A Walk-through: How to diagnose and fix GT4 headlight problems

Okay folks, since I just got all my lights working on my GT4, I figured that I'd list exactly what I did and how I did it. While I haven't had to do all this to my 328, it's probably very similar -- so it should apply in some sense to all 3X8s.

The setup: GT4s have four lights. When the lights are turned on to the dipped beam setting, the two outboard-positioned lights are on. When the stalk is moved to the bottom click, all four lights come on. The two inboard headlights that are only active with MAIN BEAMS are two-prong/single filament. The others are three-prong dual filament -- and have a dipped/low filament and brighter high beam filament for the main beam setting.

On my car I had one right-side low beam working on dipped and the left was out. When the main(brights) were selected with the stalk, both left side lights came on, but nothing on the right side.

So here's the checklist:

1) Check your fuses. On the GT4 there are four fuses starting at the left of the right-side fuse box. The first two are MAIN BEAMS (brights), the next two are DIPPED (regular).

2) Check power at the fuse box: Take a circuit tester (they're $4 at Harbor Freight if you don't have one) and simply clip the ground to the metal latch (not on the door, but the box itself) then flip the headlights to the dipped position and touch it to the top of both fuses of the dipped beam circuits. The test light should come on. Flip to main beams and test all four, because all should be on with the main beams. If all come on, step 3...if all but one come on-- check that your fuse box isn't melted from corroded contact bars in back. (There are two power wires that come in -- red for MAINS and yellow for DIPPED, but there are brass bars in back that jump the power to the second fuse -- If you see deformation of the plastic, contact Birdman and get new fuse blocks.) If both of either the dipped or main beams don't light and the blocks look good -- step 5.


3) Pop headlights up and disconnect battery. Disconnect a single the headlight that isn't working and test power to the light plug connector. If you have multiple out -- start with the dipped beams first. The main beams are easy: one ground and one power. The dipped beam sockets are three-pronged, which means one ground, one power for the dipped filament and one power for the high beam filament. Reconnect battery and connect the test light ground to the black ground wire and shove the test prong into the power for the dipped (green/black wire) or main (green) -- whichever you've selected with the headlight stalk. If you have power to the socket, but no light: REPLACE YOUR HEADLIGHT!!!

Headlights are: Sylvania parts 5001 and 5006 - both halogen. Available at any auto parts place.


4)If you don't get power here, but had power to the fuses, you most likely have a ground issue. Check the ground right behind and to the right of the driver side headlight pod.

5) If you didn't get power to the fuses -- the next step is simply to replace your headlight RELAY. Don't worry -- relays are available at any auto parts place. (If you're replacing all of them, europartsdirect.com is the leader for price -- thanks SeattleM5 for that tip!!!)

GT4 relay panels are either next to (or just under) the fuse box, or are accessed by removing the vertical part of the passenger footwell carpet and unscrewing the metal plate behind it. (Takes two minutes, at most.) There are two relays that specifically deal with the actual lights themselves. The top right is the "flash your brights to pass" relay- Bosch part 0332204101 (or NAPA part AR201).

The second one in on the top is the more important relay -- a Stribel SR9833 which is no longer made. Remove it and replace it by driving down to your local NAPA and getting AR289. (You can also go to O'Reilly and cross reference it against the AR289 or get a Bosch via europartsdirect.com...) This part is around $25.

If your headlight pods don't come up at all -- the fault is also usually at the headlight lifting relays. Bosch part numbers still can be cross-referenced to new numbers.

By the way -- many of the relays (such as the cooling fan relays) are Bosch 0332014113, which translate to modern BSH001516 or NAPA AR703 (but they have brackets on them with AR703.)

6) If after your relay is replaced, you still have headlight issues, it could be in the contacts of the control head (or if you have absolutely no lights, in the wires of the stalk.) Proceed cautiously, not because it's at all confusing or technical, but because opening up the control head is a pain in the tailpipe with many fiddly parts that go flying and are a $#(*& to fit back together. BUT, you simply remove the steering wheel, the nut (requires a special socket -- or make one with a grinder and a Harbor Freight cheap socket), hub,signal cancel ring, and then the signal pad. Underneath on the left are the contacts for the lights. If you see the brass contacts laying in parts on the bottom of the column, there's your problem. Otherwise, you might have worn the contacts out, or have corrosion. THERE ARE SPRINGS AND BALL BEARINGS THAT WILL SHOOT OUT SO DON'T TAKE THESE OFF UNLESS YOU'RE OUT OF OPTIONS. PM me and I can give you tips on removal and replacement. (Like drilling the top of a bodywork stud-gun stud and adding a little bearing grease to cup and hold the ball bearing, wrapping the end with a little tape for better holding bending it for better angle of attack so you can get the ball bearing back in against the detent spring..and also and wrapping reversed tape around the contacts and springs to hold them togther while you get the stalk back on.)

CASE STUDY: What happened on my car-- I replaced the headlights and that temporarily fixed things -- the next morning I lost dipped beams. My fusebox was melted, so I cut out and replaced (with jumpers) the offending circuits. I noticed I also had lost power to the dipped beam fuses (and hence no dipped beams), so I replaced the MAIN BEAM RELAY and TA-DA -- everything is back in business. (I had previously fixed my broken stalk and replaced the twisted/stretched green and black wires, which meant I was able to test the contacts in the control head.)


Hopefully this helps someone in the future. (And I hope I didn't forget or recollect incorrectly!) Add to or correct this as needed!!!

Cheers,
Sam

 

Thank you! This is very useful to me, now printed and in my "todo" binder.

/Pero

 

I wanted to make sure that I added an update:

Despite what the manual says about the "flash to pass" relay being Bosch part 0332204101, this is not the case. When I went to drive the car yesterday, the BRAKE FAILURE warning light was illuminated and wouldn't turn off. (The brakes are fine/fluid level good.)

I put a 0332014113 back in and it went away.

 

Friends,

How do you flash your brights to pass. My SR9833 I think was acting up (the main beam relay) but it had a Bosch 332 014 113 in there since 1994, replaced it with a new one and seems to be fine.

Will look for the cross reference to the correct one.

Rob

 

The thread may be too old, but my lights simply cut out driving home the other day, both lights dropped back down and then no lights. I am assuming it is the relay as it was sudden and 100%. Fuses are all OK. Going through the list of relays and trying to figure out the right ones. Am do you figure I right in my thinking?

 

Newbranch,
Yes, follow the tutorial and you should come up with the fix. If not, check back with us. And welcome to F-Chat!

 

Sam, thx for the tutorial. I went to drive at night and no running lights, headlights, low or hi, or dash lights. Turn signals, hazards, and brake lights work. Went through step one above and no power through right side fuse box light fuses though there was continuity between the contacts. Relays next I guess. Am I on the right track? Thx, Blaine

 

So here's an interesting one. I have an Australian early Dino 74 GT4 and I'm wondering about two specific things.

1. When you rotate the headlight knob to ON, and the stalk is in the upper or PARK LIGHTS position, do the buckets come up, but no lights are on in the buckets?

2. With ignition ON and NO headlights, what happens when you pull highway flash.

3. With headlights on LOW beam, what happens when you pull highway flash.

Somebody in a previous life has been into mine and cut out wires and I'm trying to reconnect back to factory specs, but the wiring diagram does not 100% agree with my car.

 

What 308GT4 "wiring diagram" do you have? Do you have the 91/74 (euro), 100/74 (early N.A.), and 144/77 (late N.A.) OM schematics, and do all three have something in the headlight wiring that obviously doesn't match your stock headlight wiring?

 

Steve, om the top left corner it says 100)

So presumed it was correct for my car which is an N/A 74 model Dino.

I've attached a PDF of the fuse box. One page shows what the wiring diagram expects, the next page shows what my car actually has.

 

So the real issue is this:

Years ago a previous owner bypassed the headlight switching as the rotational switch broke and then the column stalk switch broke. So being very unkind to the car, they cut the loom each side of the large white plug that goes to the column stalk switches that deals with headlights and highway flash.

Then they butchered the wiring and fitted a three position rocker switch in the dash. Then they threw the headlight relay over their shoulder and punched threee wires directly into the fuse board to operate a foot dipper switch for high/low beam switching.

So out of the column I have the following 6 wires to re-connect:

Heavy black wire (which I thought bought power to the high / low beam positions of the stalk)
Heavy red wire (which appears to me to be power out to high beam)
Heavy yellow wire (which seems to be power out to the low beam)
Two heavy light blue wires which are in and out to the highway flash
Light weight green wire which seems to switch earth from the rotational light switch on the stalk

On the loom side that they cut, the wires don't marry up. I have a light red, a heavy yellow, a heavy black and that's about it. The rest appear to have been deleted.

Logic is not prevailing because this is what I expected.
Black heavy wire would come off the headlight relay 87 terminal which was activated by rotating the headlight knob connecting Earth to Pin 85. This would also send earth to the lift motor control relay and lift the buckets.
Heavy Yellow and Red would power high and low beams and go to two distinct points on the fuse board, then off to the lamps.
Highway flash would get power from 87B so would be active when the headlight relay was active and the other blue would go to the fuseboard and connect to either high or low beam, depending on how the flash actually works.

Thinking that in most cars, highway flash actually flashes high beam. But I didn't know how it works on a car with headlight buckets to lift.

BUT.............

There appears to be no place on my fuseboards for the heavy light blue wires.
There is a heavy yellow/black already there
There is a heavy red already there and neither the red nor the yellow/black meters through to the cut yellow and red under the dash.

There are also a couple of spares that can be seen with an ? marked against them that I can't identify but actually exist at my fuse box.

BTW: Just for information my car has no AC fitted so that relay is missing from the board, yet the wiring is probably still there.

 

That 100) on my diagram could also be the page number I suppose. It's a huge AO size black and white printout to help my old eyes.

 

Your post #11 explains a lot about the "actual" pdf of your car's wiring

First, the wiring diagram that you have might be something that F (or someone) tried to make for RHD 308GT4, but they mucked it up some. This link:

https://www.dropbox.com/s/swnl4jhmnpfny56/MUM_Dino308gt4 1975 US 100_74.pdf?dl=0

should get you a copy of the LHD US 100/74 OM (the scan quality is poor, but it is still usable). The "Left" and "Right" names for the fuseblocks are switched from what you have so let's call them the "Ignition Coil Fuseblock" and the "Headlight Fuseblock" to keep things clear. The fuse values in your actual Ignition Coil Fuseblock match what's in the US OM Ignition Coil Fuseblock so all is OK there (you can see that the fuse values in your wiring diagram's Ignition Coil Fuseblock are just the reverse order of the fuse values in your wiring diagram's Headlight Fuseblock so that's wrong and probably related to mucking up the left-right swap).

What you'll need to have:

1. The large red wire going to the top of the high beam headlight fuses either has to come from the high beam terminal on the headlight switch or from terminal 87 of the high beam relay 88 (if you have one - and, if you have one, the red wire from the headlight switch would go to terminal 86 or 85 of that relay to actuate it, and terminal 30 of that relay would get +12V from the power block).

2. The large yellow wire going to the top of the low beam fuses has to come from the large yellow wire low beam terminal on the headlight switch.

3. The large black wire from terminal 87 on the headlight relay 87 goes to the pole of the low beam/high beam switch.

4. The large green wire from terminal 87b on the headlight relay 87 goes to the top of the 16A fuse (you show this as already OK).

5. The small green (grounding) wire from rotating knob should go to either terminal 85 (or 86) of the headlight relay 87 (and cause relay 87 to actuate when the knob is rotated).

6. The large light blue wires of the flasher switch really don't go anywhere -- as you can see on the 100/74 schematic, one of them connects to the large black wire (which is +12V when the buckets are up), and the other connects to the large yellow wire (which goes to the low beam headlights) in the harness side connector. The way it works is:

If the buckets are down and you pull the flashing stalk = nothing happens
If the buckets are up with the headlights "off" and you pull the flashing stalk = the low beam headlights flash
If the buckets are up and the low beams are "on" and you pull the flashing stalk = the low beam headlights glow a little brighter
If the buckets are up and the high beams are "on" and you pull the flashing stalk = the low beam headlights flash (while the high beams stay "on")

The "jumper" you show on your Ignition Coil Fuseblock connecting the (always +12V) power block to the top of the window switch fuses is a kluge to have the window motors operate with the key "off". If you still have a window motor relay, the tops of those fuses should be connected to that relay's terminal 87.

Give a shout if something else comes up...

 

Thanks Steve. I'm going to need to sort out this heavy yellow/black that's coming off the top row of my fuse board. That's the one not making sense. Heavy yellow straight from the column (low beam) should go there as you say.

I'm going to try and do a relay wiring diagram next to show the same thing, what I should have, and what I actually have. I'll look at getting that sorted tonight. Trying to get the best ot of the daylight to finish my shed frame right now. Here's what I'm building. It's about 50' wide x nearly 90' long, 16' at the edge to 26' high in the middle. Doing it all myself. Design, welding, erection, everything.

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Please find attached a PDF that I created today of my actual relay board compared to what my wiring diagram says I'm supposed to have. I created the drawing by first looking at the board face and showing where I have wired pins with no relays fitted and where I have relays fitted. Then I flipped it upside down crawled into that horrible tight space and tried to dissect the wires enough to see where they actually went to on the rear of the relays. For the sake of the drawing, I used 85 to the left side of the relay and 86 to the right side. 30 always at the top. 87 to the bottom and 87a or 87b shown in the centre.

So this is making it very difficult to understand where to hook my headlight stalk controls into the system, especially given the variation in colours and quantities of wires going to the actual relay board compared to what I should have.

Steve, I downloaded the file, but unfortunately even on my big monitor at 200% I wasn't able to follow the wiring diagram, as you said, the scan just wasn't good enough.

 

Try harder!

I'm feeling more and more that you should put no trust at all in the "wiring diagram" that you have - for example, not having a relay D (under control of the rotating stalk knob switch) just seems impossible. What I can offer is how to hook up your system like the US 100/74 schematic; however, I'd need some up front questions answered and would make some comments:

1. On your relay diagram, you've labeled all of the horizontal center terminals as "87a" and all of the bottommost horizontal terminals as "87". This is fine for identifying the physical positions, and I will call them "position 87a" and "position 87" going forward to match your convention, but the different relays themselves can have different terminals in those locations.

2. You show relay D as presently being Bosch 0332014125. On the internet, I see this relay has terminals 30-85-86-87-87 - can you confirm that this is true? The relay terminals should be labeled on the relay itself, and there should be a internal relay schematic shown on the relay outer case. In order for this system to work correctly in the typical F fashion, this relay D needs to be of the type of relay with terminals 30-85-86-87-87b (e.g., Bosch 0332015006). This needs to be of the 30-85-86-87-87b type otherwise the headlight bulbs would flash with the emergency flashers.

3. On your previous fuse diagram, you show a red wire connected to the tops of the high beam headlight fuses, and note this wire goes "To 87b headlight relay". However, on your relay diagram there is no "headlight relay". If this red wire actually goes to the position 87a of relay E = that would be a good thing. Please clarify.

4. On your previous fuse diagram, you show a yellow-black wire connected to the tops of the low beam fuses. Is this yellow-black wire presently connected to the position 87 of relay E?

5. On your previous fuse diagram, you show a yellow wire connected to the tops of the low beam fuses (labeled with a "?"). Do you know where this yellow wire is connected at the other end? (I believe it should go to the yellow wire of the headlight switch.)

 

Morning Steve,

I'm wondering if my diagram may have been mixed up and could even be from a 308 GTB. The guy gave me his GT4 workshop manuals and this large diagram was in it. Shame I couldn't see your version.

Got to be a very good reason why so many of the colours running to and from the relay board don't sync up with my car.

The car certainly has a D relay and the relay board legend says that it is "external lights'. But this doesn't correlate to the wiring diagrams that I'm using. What number is that D relay on the actual schematics? Mine only shows a numbered relay 87 being the main beam relay.

1. Yes, I understand that many of the relays may have 87/87 or 87a/87b or 87/87a. This was just my way to quickly identify wiring positions on my drawing.

2. The current relay in D position (external lights) is a Bosch 0332014125. It has two 87 pins. Although it's a metal cased Bosch style, it has a standard relay hanging tab fitted, designed to be screwed onto something, so obviously not original to the car. Does Testarossa have an 006. I can steal one from there.

3. Yes. I removed the red from the fuse board so no feed back possible. Continuity checks directly to centre pin where relay E should go. Check.

4. Yes. Yellow / Black wire connected to position 87 where relay E should go. But I don't have a relay E fitted. I'm going to borrow the blue strip K relay from the Testarossa to get going until I can replace it. Pretty sure that's the correct one to use. Previous owner tossed that relay over his shoulder and plugged in a foot operated dipper switch into the terminals on the board where the relay should go!

5. I traced that wire last night and yes, it is the yellow wire that was cut which should marry up to the yellow wire coming out of the column stalks. I've temporarily re-connected these at the moment.

In relay position F, I have no relay nor any wiring. Is this where highway flash (two blue wires from column stalks) should connect to. Wonder why there is no highway flash on an Aussie car. Wouldn't mind making this work, even if it flashes the fogs, Handy to use if someone fails to see you.

 

Here's a picture of the relay board showing the legend and the current relays. Clearly there are a couple of relays hat have been changed and I need to locate replacements to put it back to standard.

Don't mind the connectors fitted where relay E should go, there for testing and tracing purposes.


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So clearly the small green wire from the column rotating switch should trigger earth to relay D. And the heavy yellow wire from the column is connected to the fuse board in the right place. So relay D get's triggered and lifts the buckets, and then also would connect to E to supply power to the column stalk which then switches park/low/high.

The outstanding issues are that there is a heavy black wire cut on the column. When I connect the Fluke to the black wire and the yellow wire in the low beam position of the stalk, I get continuity. Then connect to the red wire and move to high beam and I get continuity. So I thought that the black wire must have supplied power to the switch, and then the yellow and red should run back to the fuse board to feed the low and high beam lights. But there appears to have been no heavy black or heavy red wires cut on the loom side to re-connect to.

Don't get it why people have to butcher things, only for others to have to piece them back together years and years later.

 

Stroke of luck. I managed to locate what I now believe to be an Aussie wiring diagram for a GT4. Not sure what year, but a local bloke has had the car for a long time and the diagram is supposed to be out of his owners manual. One thing to note, it has an extra relay on the drawing. Now it shows 88 and 87 relays. Off to the copy shop to make a really big one that I can actually see.

 

Revised relay drawings attached now that I have what I presume to be the correct drawing. And printed about 4 feet long so I can see it. Far less contradiction in colours of wiring now and at least this drawing has two relays for the headlights 87 / 88.

Where I have written a value eg: F85 + No.34 this means that there are two wires. One goes to Pin 85 on relay F and the other goes to a unit marker with a number on the schematic in this case the high / low beam switch.

 

Sounds like you've made a lot of headway and have a much better wiring reference. On the US schematic, the "External Lights" relay" is labeled #87, and the "Main Beam Lights" relay is labeled #88. It is not unusual to have no wiring and no relay in the F-"Flash" relay position - F Models/Versions that would have a Flash relay also have to have additional front lights (not in the headlight pods).

The D relay "External Lights" MUST be of the 0332015006 type with the "K" on the outer case (so that the large black wire in position 87 and the large green wire in position 87a are not connected when the relay is unenergized). On the US 308GT4 100/74 schematic, it is shown as "Stribel SR0833", but this is identical to the Bosch 0332015006 (and on subsequent F models that use this same relay and same wiring scheme, the Bosch 0332015006 part number is shown).

I'll have to defer to your reference on this one. I think the way this works is the red wire from the headlight switch (connects to position 86) closes this relay E when the high beams are selected. When this E relay is actuated, the white power block wire on terminal 30 is connected to both the red wire in position 87a and the yellow-black wires in position 87 (this illuminates both the high beam and low beam bulbs). The benefit of this arrangement is that the very large current to run all these bulbs does not pass thru the headlight switch contacts. This would also require using a Bosch 0332015006 relay; otherwise, the high beams and low beams would always come "on" together.

When the low beams are selected, the yellow wire supplies +12V to the low beam fuses. The current to run the low beams does pass directly thru the headlight switch in this mode.

And, finally, the white wire in the position 87a of the G "Glass Lift" should go to the tops of the Window Switch fuses (and the connection between power block wire and the tops of the Window Switch fuses removed) so the windows only operate with the key "on".

 

Forgot to ask -- What are the wattages of your low beam and high beam bulbs? I'm interested in comparing them to the US wattages (as on the US version, the headlight wiring architecture is more low beam only or high beam only, not both together).

 

Actually, you will need to look at your actual headlight architecture and compare it to the "wiring diagram" as well. For example, on a Euro 308GT4:
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#2 = a one-filament high (main) beam bulb
#3 = a one-filament low (dipped) beam bulb
So for low (dipped) beam operation only the low (dipped) beam circuit is energized, but for high (main) beam operation both the low (dipped) beam circuit and the high (main) beam circuit are energized at the same time.

However, on a US version 308GT4:
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#2 = a one-filament high(main) beam bulb
#3 = a dual-filament bulb with one for high (main) beam and one for low (dipped) beam
Consequently, for low (dipped) beam operation only the low (dipped) beam circuit is energized, and for high (main) beam operation only the high (main) beam circuit is energized.

Anyway, just want to point out this difference and the need to know what your headlight architecture is determine how to wire it -- maybe the previous modifier also mucked with the headlight bulbs and their wiring too

 

55 watts each Steve.

So thanks to your assistance from afar, I have operational lighting switch and stalks, on this car for the first time in 20 years.

BUT....................it definitely appears that Aussie cars are not designed to have flash, no wiring and no relay to that position is a bit of a giveaway, even if the local wiring diagram shows the relay and all wiring.

So I had a bit of a think about this. The way Ferrari do it seems odd. Why flash only low beams, but this only works when pods are up, so parking lights have to be on anyway.

Flash etiquette here may be different to Europe or USA. We tend to use flash in only two distinct circumstances.

1. Driving along and warn oncoming drivers that there is a hazard they are approaching, like an accident or a speed camera or police car.
2. Driving at night and using low beams and some dick is coming the other way and hasn't dipped his high beam, give him a quick flash to remind them. This is probably the most used flash.

So I'm going to insert the four wires required and a flash relay and wire flash in to be operative. Just need to feed power to one blue wire from the column, take the other blue wire to 30 on the relay, take power to 85, look green out of 85 on L and loop to 86 and then 87 back to the fuse board and piggy back to the red that runs the high beam. This should give me a high beam flash when the pods are up.