Strange issue here. Just replaced the heater core which obviously involves moving things around, though it’s worth mentioning I followed Michael Neal’s method so I did not tear apart the entire interior. Just removed the steering column and unplugged things in the way.

Everything has been put back together but some fuses under the driver’s kick panel are only getting 4-5V with the engine on. Engine off it’s between 0.2 - 0.8V. I haven’t checked every fuse but most of them are this way, but I can confirm the one that sends power to the door locks works fine.

A couple months back I had an issue with the fuses and successfully performed the fix for the fuses that involves wedging small pieces of rubber between the copper prongs so I can confirm the copper prongs are tight.

Any ideas how so many fuses (but not all) can receive partial voltage? Never heard of such a thing. The ones that aren’t acting up are reading the full 12.48V so not the battery.

 

IF, these fuses are Ign ON powered, then I suspect the Ignition Switch Electrical Section is the culprit.
Getting VERY common now as age creeps in.
Easily removed, dismantled, cleaned, and refitted.

I have a PDF on this and will add to this post when more time is available.

PDF attached as promised. 9PM Adelaide time.

 

Hi Grant - Good write-up on the Ign, Sw. Thanks
Do you know if it's the same switch on the facelift cars?

 

Were the voltages BETTER before the work? Were they tested previous? Just wondering

 

I would look carefully at the wiring diagram and then work backwards, from the supply side of the fuses, testing the voltage at every stage or connector, until I found a true 12 volts. Then the source of the problem would be pinpointed.

 

Thanks Grant, I’ll look at my ignition switch this evening.

Jay - yes they were all performing properly before the work.

Greg - that was my initial thought as well; I guess I was hoping someone might provide a simple one shot solution I had overlooked (some almighty fuse or something). Though to his credit, Grant might’ve.

 

Was under the driver kick panel testing voltage on the back of the ignition switch when suddenly the wiper started working. What do you know, the ignition protection relay is sort of faulty…I bumped it with my head and that completed the connection.

Had to share this in video form:

 

Beer O'clock in my opinion.

Always the simple things.

 

Unfortunately while replacing the ignition protection relay yielded 12V to the fuses that were at 0, the horn still doesn’t work. Here’s the weird part:

Pins 85, 86, and 87 are supposed to have 12V with the ignition on. I get 12V at 85 and 86 but about half that at 87 (like 5.4 or something).

Bad relay, right?

I‘ve tried four different ones and same thing on all of them.

How is this possible? I thought maybe a bad ground but I’ve gone so far as to connect the purple steering column ground wire to the engine grounding strap and no difference.

Any ideas?

 

Check the frontmost fuse in the LHS of the engine bay inner wing. This controls the fan, but ALSO - and this is NOT shown on any factory wiring diagrams, the horn circuit- which in effect has two fuses in its system.
Cannot help with the relay!.

 

Not sure what year you have but 80s vintage horn relays...and perhaps later...were wired like this:

86 = 12v with key on
30 = 12v constant
87 = 12v output to horn
85 = ground/trigger

So you wouldn't have 12v at 87 unless the relay was triggered. And if you don't have a full 12v on 30 then you'll never have a full 12v on 87

Does 85 go to ground when you press the horn button?

Cheers
DD

 

You know what you’re right; I thought something was off about this wiring diagram. So let me rephrase: with ignition on I’m getting 12V at 85 and 86, but only 5-6 at 30. I’ll check if 85 goes to ground with horn push.

 

I completely forgot about that mystery fuse. I’ll give that a shot, thanks Greg.

 

In that case, lack of supply voltage to 30, I agree to look upstream at the source....the fuse. Most likely some corrosion at the fuse

Cheers
DD

 

For my own education: if there’s corrosion somewhere upstream, wouldn’t 86 also be low on power?

 

Greg you are the man. Did the fix on that fuse by cramming a piece of rubber next to the copper prongs, bingo - the horn works.

On a side note, I discovered that you better not use anodized screws in the back of the steering wheel to hold in the horn pad; they do not carry current so you have to use “normal” steel screws.

These cars are hilarious.

 

Depends how far upstream you go and what tributary you take

Voltage to 86 comes from a a different fuse, via (from memory) the protection relay then to a fuse. Voltage for 30 comes from the main "+" junction post on the firewall then on to a fuse

Cheers
DD