Does the janitor look at your keychain with admiration?

No, no janitors admiring enviously my heavy set of keys. I just replaced the lock and cylinder 2-3 years ago. My key chain is fairly light. I wonder if the switch on the column could be at fault.

This weekend, I will clean up the body ground strap.

 

I guess the problem is the issue only manifests itself when I am hauling and is definitely more obvious after dark. I am going to try diddling the steering column ignition switch and keychain in the dark. Now does that sound kinky, or what ?

 

Will definitely try that.

 

Now that’s really weird.

Once the speedo starts tipping from 80 to 90, both the turn signal dash lights come on well as the high beam dash light. The engine seems fine and not cutting out.

I lightened to the key no effect.

Jiggled the key and the body-frame ground (wile stationary) nothing happened.

This is really weird… and unsettling

 

My next test will be to see if it does this with headlights off.

 

Looking at a diagram, the front ground looks common as well. Tomorrow I’ll check out health if that area.

 

Increasingly thinking this is the issue. I seem to recall the headlights also dim. Maybe at 80-90 the wind pressure is such it’s compromising the ground ?

 

Might want to check the turn signal/running light (1157) bulbs on all four corners of the car. Make sure all the elements are in good shape, and the bulbs are installed correctly.
The vibrations at 80mph+ could cause a broken element, or incorrectly installed bulb to create a short and back feed power through other circuits.

 

Well, we have more conclusive data but not quite a smoking gun IMHO. And let’s hope there were no speed cams out there

I found what looks like the ground from front headlight harness. It doesn’t look like the stock location but it does seem to be the OEM wire coming out of the harness. IIRC, the stock location is on the radiator support.




Note the blue paint on the tape. There was some blue overspray on the eye connector and the frame area didn’t look like it was sanded clean through the black paint. Still, I have seen worse that nonetheless worked.

So I sanded everything a went for a drive testing two things. 80-90 mph with and without the headlights on.

With the headlights on, the high beam dash light No longer comes on. The turn signal dash lights are much weaker and require a higher speed to activate.

With headlights off, no dash lights come on. I even pushed it all the way to 100 mph Nothing came on.

So, we seem to be onto something - but not there yet.

 

You I've following this thread since I posted in it and I have to laugh because you guys are all shooting from the hip. As I said earlier the common denominator is the dash is not grounded, period. OP do yourself a favor, stop dicking around and run a jumper wire from the negative battery terminal to the dash ground and see what happens.
And if that doesn't work it means the ground is broken is further up the line. Try it with the gauge fuse removed.

 

Thanks. I appreciate your feedback. I’ll try a jumper. It never occurred to me that the ground wire could be compromised higher up. Good point. Though I would have thought that tugging on it would have revealed something.

You are definitely onto something; what you’re saying makes sense, but , with all due respect, only partially. I spent a lot of time poring over the wiring diagram searching for the common denominator and, unless I’m mistaken (quite likely) it can’t be the dash ground.

For these three lights only to come on and the heads lights to dim the common failing ground would have to be up front. If the ground there fails the current feeds back to those three specific bulbs and would dim the headlights. Think about it. If the headlights are not on, the problem disappears entirely because there is no current that can feedback to the three bulbs.

Why is it only these three dash bulbs and not the entire dash are acting up ? Why is there no issue with headlights off ? Why did improving the ground up front have a positive effect? Why is this only acting up at speed ?

I think the ground wire of the front harness is compromised. Another point you made.

I’m also eyeballing the alternator. Something else is bothering me. Why would this only be happening at high speed… unless maybe it’s higher rpm related ?

This doesn’t look right either and the case ground also looks anemic. I do know this is a 140 Amp alternator that can be hooked up with one wire.

Now I gotta remember how to do a voltage drop test…

 

Aaaand the plot thickens again. Past midnight here and I nipped into the garage*. I was planning on doing a voltage drop test but couldn’t quite figure out how to do it on the ground side

Then it occurred to me, I cleaned the ground location, but it’s not the stock location - that is on the radiator support. I should check if it’s any good. So I removed the wire and checked the ground location. Very, very poor despite being down to bare metal. I’m amazed the horns and lights even worked.

It’s not the wire. It’s the front end of the frame. At higher speeds, the air pressure must be pushing down on nose further compromising the ground.

Tomorrow I’ll add a ground strap there to see if that changes anything.

*curiosity killed the cat but satisfaction brought him back

 

Hm... a second ground somewhere...

So there are two grounds there. I remember replacing my radiator core support a few years back; mine was totally rusted out. However, I don't remember having a removed or reinstalled that ground.

Hmmm ​​​​​​​

 

1st your alternator ground wire has seen better days...
2nd the location of that ground is not correct...There is a 5/16" threaded hole near C/L on the right side, just don't install a bolt over 1/2" long.
#2 the Front Of Left Fender Skirt ground in the diagram shows it up top on the core support, it could also be at the bottom of the core support I drew that location is as well.
I know your car is earlier but ground locations should be similar to later years.
1977 locations.
I have added red stars and numbers to there locations from what I have seen of the photos you posted.

 

Well, this is a slice of pure sliced gold Many thanks !!! I searched for the OEM harness wire for the alt. I can’t find it yet. I did see the ground bolt hole you are talking about - easy fix… if I find that harness ground

As for the radiator support…


Well hello there.



I bet you go here.

 

Found the alternator ground wire… cut short and meticulously taped up. I extended it and reconnected it to the correct location with the proper gauge wire.




I also found brown wire with a white stripe. I’m guessing that’s from the ignition switch to activate the alternator. I don’t think it’s necessary to reconnect that one on this alternator.

So I took the car for a test drive and: solved !!!

Thanks everyone for your input. I couldn’t have done it without your help.

Now, I should probably restore the engine mount to frame ground and the exhaust pipe ground.

 

You're still not home yet. You always had two problems, your instrument panel lighting or/and bird cage ground and your front lighting harness ground. By repairing the front lighting harness ground the front lighting return is no longer finding a path back through the instrument panel lighting. I know this because of this statement:

If you were to do a voltage drop check between the instrument panel ground and the cars frame you probably find you are losing a bit there. A bad front lighting harness shouldn't affect the instrument panel because the instrument panel has its own ground, but it didn't. See where I'm getting at. Lose that cheesy braided ground strap and put something more substantial between The birdcage and frame.

 

Processing, processing, processing - noggin' heating up

Yep !!! I get it. Would replacing with a heavy gauge wire be better than another braided strap ? I never understood to point of bare braid over sheathed copper.

 

To make my life easier I spang for something I should have acquired a long time ago



No clue how it works but I’ll be it will be helpful