Fuse blowing: Air pump/turn signal/glass lifter/rad fan relay

Hi all,
I am hoping to get some help here. The subject fuse is blowing, and the parking brake light mysteriously comes on when it does.

I am not super versed in electrical work and troubleshooting, but I do have a multimeter.

In terms of other clues as to what may be going on, I did recently replace the window switches (it had been wired for 5 pin units, and I replaced with new 5 pin units), but the windows (and blinkers etc) were all working fine for some time after that swap.

I drove it 3 weeks ago which is where I first experienced the blown fuse and parking brake light. I replaced the fuse at that time and the radiator fans came on straight away (which I was glad about- seemed to be fixed).

This time, I was on the road, observed the condition with blinkers not working and red parking brake light on, so I pulled over in a parking lot and replaced the 15A fuse. Even though the car was maybe 195 degrees (similar to what I recall for last time), the fans did not come on this time (but the fuse did not burn out immediately or anything either). Then when I started driving, I noticed the red light come on again, and blinkers not working. I presume it must have blown maybe when I put the ignition on and/or the car started.

The amp meter gauge generally shows quite high (like pinned to or beyond +40 when over say 2,000 rpm or so); not sure if this is normal.

Thoughts on what would be reasonable to do next to diagnose? I read something about the parking brake light illuminating due to ground sneak path… and maybe just a second order thing and I should try to find the short.

I was thinking of measuring the voltage and current across the fuse terminals with the ignition on with my multimeter, and then playing with the blinkers and window switches to see if anything changes.. short of that maybe pulling out the window switches since it is a thing that changed and see if the fuse no longer blows.. (though they were working fine for some time as I indicated earlier).

Any thoughts are much appreciated!


Sent from my iPhone using FerrariChat

 

You mentioned a lot there. I'm going to comment on one small item - I believe that some of the "newer" cars had the brake light show if there was low fluid. It doesn't make sense that that would occur after a fuse blows, but you might want to check the brake fluid level.

 

Thanks Ken.

It could be that, but the parking brake light is only on when said fuse is blown, and I read elsewhere that this can just be the current from the short I have taking another path that happens to go through that light, which makes sense to me.

Through troubleshooting, I was able to confirm:

1) I have a hard short through that circuit, which only manifests itself when the ignition is in the on position.

2) it is not my window switches (short is still there with both positive window feeds in the center of the two 5-plug switches unplugged)

I am somewhat at a loss as to what to do next.. are there any known component failure modes in the air pump, turn signal, safety harness circuit (what is that? Seatbelt check?) and radiator fan relays?

I guess next I’ll try to figure out where the turn signal and radiator fan relays are located… though to be honest I am not positive what I would do with that information…



Sent from my iPhone using FerrariChat

 

Unfortunately, the pdf copy that I have of Angelo Wallace's translation of the 246GT/GTS Workshop Manual is of such poor quality that the schematics are virtually unusable. If you can get me a better copy of the schematic shown on page 56 (which I think is for a US 246 since it has the air injection pump) or some other readable copy of a schematic for your car, I'd be glad to give it a look over.

 

Thank you Steve!

Here are some high resolution shots from the chassis supplement book I have.. does this help?

I am thinking that the fact that the fans did not come on today when I put a fresh fuse in, when the car was hot (without key in) may be a clue? Because I am pretty sure they *did* come on in the same situation before this was a “hard” fault/short. So maybe it is something with the fan relays? (But I am absolutely no expert here as you can surely tell!)

Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login


Sent from my iPhone using FerrariChat

 

I think my high resolution was not so high. I’ll try maybe a pdf scan tomorrow…


Sent from my iPhone using FerrariChat

 

Greg

Wiring issues on the Dino are a nightmare but can be easily solved by working in a logical manner. First step is isolate the problem fuse and check for short circuit in the wiring. Disconnect each component in turn served by the fuse and find out which one is the culprit.

Here is a coloured wiring diagram produced by Adrian Le Hanne, very useful to get blown up to A3, may not be applicable in all cars as they changed over the years but its a good starting point. It does contain some minor errors but on the whole its very good.

One thing that does concern me is the high charging rate, you could have a big issue here if its not solved. The ammeter wiring runs through the main loom and at the sustained charging the wires will get hot and melt. There are lots of posts on this, use the search function to find them, I had similar problems in this area and it was a few items causing it, bad electrical connections, earthing and voltage regulator.

Tony

 

Yes, please try again in pdf, if possible -- being able to resolve the very small item numbers is what's important (like the tiny item numbers for the various warning lights in the tach and speedo). That does look hopeful as being the right schematic for a US 246.

That might help some if they use the same numbers for the various item, but I think it is for a different Dino -- not only is there no air pump in the item list (it may be there and not labeled), but there's no parking brake warning light switch nor parking brake warning light shown (The Wallace translation has ~5 schematics in it, IIRC, and none are clearly labeled for which Dino they are for). Since Greg reports some very strange behavior from the parking brake warning light, it may be the best thing to look at for how that could even happen (in the typical parking brake warning light architecture, having any upstream problem cause that symptom is near impossible -- so the 246 parking brake warning light wiring design must be something pretty strange/untypical).

+1 -- it's like the ammeter and alternator behavior are just confirming that there's a huge short somewhere.

 

Ok, thanks Tony! I will broaden my search here to more generic electrical problems. I am sure there are posts that say where relays (and other components in question here) are where on the car as well, and your color plot should help me determine which ones to unplug and then check if the short is still there at the fuse. And thanks for the caution on the high current. I will plan not to drive her until this is worked out! I have attached a high res pdf of the electrical wiring diagram I have from my factory chassis service manual abstract in case it is of use as well.

 

Perfect! Please give me a day, or so, to have a look.

 

Steve- thank you so much for the offer.. any help trying to figure this out is much appreciated, and as I recall the Ammeter was not as high prior to this, and your explanation that the alternator is trying to "feed" the short makes a lot of sense (and surely is not great for the ammeter to work that hard). I kept the revs down when I observed this was happening. Another possible clue is that the parking brake light was dimmer (at idle anyway) the first time I experienced the problem (prior to replacing the fuse and "fixing" it temporarily). Now with what is apparently a harder short, the parking brake light is visible even at idle.

 

The charging issue could be a easy fix and yes dont drive until resolved. Mine was a cumulation of bad bulkhead / firewall fuse block & connections. In the end I rewired that circuit with upgrade wiring and never had a problem since.

These wires can get very hot if its not dealt with, as they run in the main harness it could have shorted out.

Tony

 

OK, the bad news is that the 246 schematic that you posted does not have a single fuse running the items in your thread title (and it seems to have some serious wiring errors on it, but it doesn't matter because we won't use it). The good news is that I (remembered that I) have a copy of the 60/72 OM Supplement for 1973 US 246, and the schematic in it does have a single fuse running all of the items in your thread title -- copy attached (although it also seems to have some wiring weirdness on it, too). My first advice is to find relay item "89-Safety belt electric circuit relay (SIPEA T10-12S)" and unplug it and see if your parking brake warning light then works correctly (unfortunately, unlike later F OM, there doesn't seem to be any diagram in 60/72 describing the relay locations) -- i.e.,

key "on", engine not running, parking brake "off" = parking brake warning light "off"

key "on", engine not running, parking brake "on" = parking brake warning light "on"

You might also give a little shake to (the unplugged) relay 89 to hear if anything is broken and rattling around inside. If the parking brake warning light behavior is still bad with relay 89 unplugged, give a shout back, and I'll try digging deeper. If all is good with the parking brake warning light behavior with that relay 89 unplugged, see if the ammeter is now better behaved (and/or if that same fuse blows) when the engine is running.

 

Ok great thank you! I will try to find that relay 89. I guess I’ll search the forum, and also physically look at the relays below the fuses for numbers/indicators.. I wanted to mention that the parking brake light had never illuminated in the past, whether the handbrake was pulled up or not, so that may be another clue.. I suspect that does not change anything with the recommended course of action. I have never tried to troubleshoot that. Will let you know what I find here..


Sent from my iPhone using FerrariChat

 

No, no change to the course of action, but it might change what "OK" behavior is -- maybe "OK" should be the parking brake warning light not illuminating when it shouldn't and the fuse not blowing (rather than the parking brake warning light being "on" when it should be "on").

The "switch" in the parking brake lever mechanism is usually a very crude thing that can get bent up and malfunction (either "on" when it shouldn't or not "on" when it should), but no matter what's wrong with it, it should never blow a fuse.

 

Thanks for the clarification, Steve, and I really appreciate your very clear communication style!

 

I shouldn't have written "unplug relay 89" so casually. I should've written "unplug the wires from relay 89, carefully marking which terminal that they are connected to" and that you'd have to unbolt it to give it a shake -- I forgot that your model does not have relay sockets.

Another question: Is your unfastened safety belts warning light and/or buzzer working correctly or not?

 

Thanks for the clarification. The unfasten safety belts is not operational; there is actually a 2-wire harness that terminates ti a female white plug that is unplugged under the passenger seat.

I won’t be able to troubleshoot my Dino until Friday at the earliest, and am very much looking forward to doing so..

I am hoping/assuming the relay will be around where the other relays are…

Will let you know!


Sent from my iPhone using FerrariChat

 

You must have more "undone/not working" than that -- that plug on the passenger side seat is just for the passenger side (there is a switch in the seat itself to detect if a person is there and a switch in the seatbelt receiver to detect if the seatbelt end is plugged in, or not) -- the Driver's side also has (different) switches working in parallel to activate the unfastened seatbelt warning light/buzzer. Not surprised if it's been disabled (as the buzzer is quite annoying ), but can also be a sign that something is wrong with relay 89 and/or a modification was done poorly. The best way to disable the unfastened seatbelt system IMO is just keep relay 89 unplugged -- only the unfastened seatbelt system will not work -- the parking brake warning light system should still work OK (but you stated you have something already wrong there, too). Will await your report.

The placement of relay 89 on the 60/72 schematic indicates that it is located with most of the other relays.

 

Ok, I was finally able to take a look and did not get very far. What I found is that only 3 of the relays say “SIPEA” on them. I circled the 3 in the attached photo, and also numbered them based on another post I saw that had US relays called out in TAV 116 (image also attached). However, I don’t have the list of what those relay numbers correspond to. I am wondering if anyone has the next page to TAV 116 that may reveal which relay may be relay 89? (I could not see any meaningful numbering on the relays themselves, though they are very packed in there, except the black one on the end, which said “T5220” and “1B” (and 12V). Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login

I guess once we find out (hopefully) which one is 89, I can cross the bridge of how to unplug it.. depending on which one it is, I may need to disconnect the battery and remove the whole panel for access..

Thanks in advance!


Sent from my iPhone using FerrariChat

 

The descriptions at Maranello Concessionaries for TAV 116 suggest that it is the 11 (USA) relay on TAV 116:

https://www.ferrariparts.co.uk/diagram/ferrari/246-dino-gt-coupe-spyder-(from-ch-02132)/116-fuses-and-relays

because:

2U = brake warning relay (so not this)
6U = A/C relay (so not this)
11U = relay (has to be this by process of elimination)

Another sanity check would be to measure the resistance from terminal 87 to terminal 30/51 on the unplugged relay 89 (relay 11U) = should be 0 Ohms when the relay is unenergized (i.e., a normally-closed relay). Although Sipea T-5220 (a normally-open relay per my internet searches) seems like not the right relay for relay 89 (and, unfortunately, the pictures of relay 11U on the Maranello Concessionaires website show no markings at all) - but might explain your unfastened seatbelt warning system not working if someone used the wrong relay.

Make sure you note which wire color goes to which terminal on the relay (the terminal numbers should be shown on the relay) -- the 246 schematic not showing the wire colors is a real negative.

 

I just checked my '74 GTS and the #11 relay is a T5170. Pretty sure it is original.

 

Use oldtimer's method - Tony said logical way, not random way

Go to fusebox and find your blow fuse.
See the big wire enter from one side to fuse, ID that is the power supply
See the other side of fuse with 5 wires - those are the circuits using power

Use a flat head screwdriver and loosen the wire connection at the fuse circuits, then remove one wire (only one please) from the circuits, tighten screw to secure 4 remaining wires then drive and do the thing that blows fuse.

If fuse does not blow then the circuit you disconnected holds the short. Track it down by following downstream.
If fuse does blow then it is still one of the four remaining, so remove one more wire and repeat until circuit is isolated.

Once you find the circuit that blows to short, follow it and trace each location for the failed part.

 

Does your unfastened seat belt warning light and buzzer system work correctly? (My quicky internet search shows that that is also a normally-open relay; whereas, the 60/72 schematic shows relay 89 is a normally-closed relay.)

 

All of the components are there but were disconnected when I got the car in '84 and I never tried to test it. I will at some point just to make sure it works.