550 Electrical Demons

After a nice drive today in 90 degree weather my 550 decided to act up. All of a sudden I lost my AC, Radio, Fans, Turn Signals, and Mirrors. 2 years ago i had the Radio and AC go but the fuse blew and had to keep replacing the fuses until i fixed my AC compressor who was apparently the culprit and re-soldering of my fusebox according to mechanic. This time all of my fuses are not blown and all good. After a deep dive on FCHAT my only conclusion is too send out my fuse box to rebuild and hopefully this will fix my problem. Has anyone had a similar situation and how easy is it to remove fuse box from car.
TIA

 

Could be your fuse box, but the first thing I would do is check your charging system. Alternator and battery.

 

Good idea will do! Only part that led me to that was car continued to run afterwards no problem and continued starting.

 

It's hard to find a common issue for these items (other than the relay panel). I tried isolating the issue to a particular plug on the relay panel, but that's proving difficult. To me, the mirror control wiring sounds like a key element in diagnosing the issue, but unfortunately, the available wiring diagrams don't include mirror control.

The relay panel is certain easy to remove. Just plugs and some nuts. I would inspect the pins on the plugs for signs of burning. I tried to isolate the issue to one of the pins on the two pin battery connection (on the relay panel), but I think if either of those two pins failed, you would have a lot more issues.

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I think that single red wire is for an aftermarket accessory.

Be sure to use the battery cutoff switch before touching anything. Sometimes the plugs can be a bit sticky... Be firm, but gentle with them.

After your fusebox has been replaced, I would be investing in some radiator relay kits (available from an FChatter on this forum) to move some of the higher currents away from the relay panel.

 

If pin #2 on the relay panel battery connector was faulty...

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... the following things wouldn't work:

Hazard warning lights, turn indicators, reversing lights
Horn
HVAC and radio
Dome lights, cigarette lighter, trunk/boot release
RH radiator fan
Rear heated window
LH radiator fan
Headlights and other external lights
Some key powered devices (controlled by relay N)
Windscreen wiper and stop lights.

Would you be able to check these?

 

Yes totally makes sense. I obviously checked fuses and they were ok, how do I go about checking pin #2 and where is that located on fuse box.
TIA

 

I mean the live battery connection here:

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I don't know if there are any pin identification marks. If there are, could you let me know which one is pin 2 (left or right). If no identification, you'll need to do some tests with an ohmmeter on the relay panel (with power off the car).

Anyway, look for signs of burning/corrosion/contamination on those two contacts (male and female).

 

Got it! I was just wiggling it around but never removed it to inspect. Will do that tomorrow and report back. To test with ohm reader you suggest unplugging battery then testing it with a meter?

 

This was only to determine which of the two pins were connected to the fuses for components such as the fans. With the 2 pin connector removed, check the resistance between the receptacle for the 2
pin connector and the fuse holders for the fan fuses (fuses removed). Most fuse holder contacts in this case should show continuity on the panel edge side of the fuse holder.

I’ll post a diagram later this evening showing the test points. This may help isolate the issue.

 

That would be greatly helpful and appreciated!

 

The wiring diagrams show the relay panel upside down, so I've had to flip the image...

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With the battery cutoff switch in cutoff, pull the K (battery) connector on the relay panel. Pull fuses 17~24. Put one ohmmeter probe on the inboard contact of the K receptacle (not the K plug). Then put the other ohmmeter probe on the side of the fuseholder shown with the red dots. i.e. the bottom dots correspond to the fuseholder contacts closest to the panel edge. Fuse 24 is different.

You should have close to zero ohms on all the fuse contacts marked with the red dot. If you don't get any reading on the ohmmeter, try putting one of the ohmmeter probes on the outboard socket of the K plug receptacle.

Here's a photo showing fuse colours in case you forget which goes where:

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You could probably pull the fuses one by one and do the tests, but pulling them all will guarantee that the fuse circuits are isolated from each other.

 

Wow, my technician periodically gets into the fuse box and checks everything to see that all is well. I never thought much about it.
I love my Tech

 

I followed your incredible instructions and thank you so much for taking your time to
do all this you are god sent. Battery un plugged, k plug unplugged as well as 17 & 24 and i got a reading of .134 ohms on all
other fusses 23-13.

 

Not sure if my instructions worked

Put your ohmmeter on the lowest ohm setting (the one which beeps), not "2Megohms". That 0.134 is 134,000 ohms.... basically an open circuit.

Put the, say, red probe on the "inboard" pin of the battery plug receptacle (i.e. the left one) and the black probe on the fuseholder.

Pull the fuse from the fuseholder you are testing.

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All your photos really tell me is that the outboard (right) pin is most likely pin "1" in the wiring diagrams.

 

For fuse 24 (only) use the rear contact of the fuseholder

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I thought i was on the lowest ohm setting
The one you highlighted is continuity, is that what i should be using?. I will pull out fuses and set it to continuity and try it again.

 

Yes I assume it also gives a readout for milliohms.

 

I went ahead and pulled out the FB and did not look good inside board. Found 3 plugs with burn marks on them and some horrible solder repairs IMO. I will be sending FB out to rebuild and we should be back on the road in no time What are your opinions on the plug ends? If they're just marked up but not completely melted, I can clean up metal plug ends and should be fine hopefully after FB is rebuilt.
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Yikes.

I see you've numbered the plugs. Can you match them up to this diagram and identify the pins which are burnt?


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I don't have all the plug colours, so I can only positively identify one of the plugs... the white one with 6 pins which you've numbered "2". That is plug "I" ... and I think pin 1 is burnt. That is power for the Left Fuel Pump.

The blue plug may be plug D (your #7)? So pins 5 & 6? i.e. both wires are for the RH radiator fan.

That just leaves the 8-pin green plug (with burnt 7 & 8 pins). An educated guess makes those the two pins for the Left Radiator Fan (on plug A).

Maybe you can confirm this ... and perhaps list the plug colours for future reference.

The pins get burnt like that because they present a high resistance in the circuit which produces heat. Pins can be quite hard to clean unless you have the right tools.

e.g. these type of abrasive tools can be used

https://www.ebay.com.au/itm/405046685873?

... followed up with treatment with something like DeOxit D5 which leaves a conductive coating on the surface of the pins/sockets.

I would recommend installing external radiator relays. There are lots of guys who have done this. Adding external relays for the fuel pumps might be a little more difficult.

 

clear 4 pin labeled I on diagram
blue labeled C on diagram
Green 8 pin Labeled A on diagram
I will buy that tool to clean metal terminals
and fan relays you mentioned. Do you happen to know a link for that also?

 

Can't be. Plug C has only 8 pins. The burnt blue plug seems to have 12 pins.

 

Nick, @Aerosurfer , if you're out there?

 

Your right my bad the blue plug is 12 pin

 

Great I will reach out to him. Thank you again for all your help!!

 

I don't know if some of your solder joints are burnt or if the light is just reflecting from them differently.

I've flipped the lower image to make the board easier to follow:

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Relay A soldering looks a bit black (Emergency Fan Control)
Relay N (Ignition Key relay)
Relay O (RH bank injector control)
Relay T (Reverse gear control)... not sure I would expect this to have a lot of current flowing through it.
etc....