The Stovebolt Site Forums The Parking Lot Big Bolts 1972 c50 lighting issues

Ok so I have a few issues going on, main thing I have going wrong is my driver brake light will not light up when brakes applied but running and turn signal lights work fine and all other lights operate as should. Other issues my right turn signal indicator light comes on when I turn headlights on but signal doesn't actually blink but it is lit up and when i use signals they work as they should.... and since I been trying to track all wiring down to fix, I found a wire coming from harness section by front passenger headlight/battery bank that is cut after a inline fuse connection which the fuse is blown and my question to you folks with same truck what does that wire with fuse go to and how should I be fixing this brake light issue or are these related and once fuse connection is fixed all works fine???

Thanks mike

Hy DIY.MechanicMike, it sounds like you have two different problems, the no left brake light but functioning left rear turn signal says turn signal switch problem to me. You didn't say which right turn signal lights up, front or rear, if it's the front I would suspect a ground problem with the headlights. You also did not tell us the colour of the wire you found, the colour would help us to identify the original purpose of this wire

I take it you haven't found another wire dangling someplace.

As 3B mentioned, the turn signal indicator lighting up with the headlights sounds like a poor ground connection somewhere, causing the current to backfeed through the other light.
Good luck! Let us know what you find.

Ok so all my turn signals front and back work. Headlights work as should. Running lights work as they should. Driver brake light does not work but passenger does. The turn signal indicator on dash board lights up right turn signal but doesn't flash, it does then flash and operate when I apply turn signal lever that direction. Hopefully this is much clearer of my issue.

Now the wire with inline fuse that has been cut after fuse I believe is for the alternator,voltage regulator, battery and I think it suppose to hook to junction box(location: front passenger corner panel in engine bay by battery) that is where positive battery cable get power from alternator. At least that's what I think, it's very hard to decipher wiring diagrams from manual to actual engine when they dont put pictures in manual of different wiring harness connections and locations. But I did what I could and this is my "edjumacated" guess lol. Hopefully somebody can push me the right way to fix this, I can post pictures of need be. Thanks mike

Sorry forgot the wire with inline fuse appears to be black.

First thing I would do is check ALL the bulbs. I know that sounds silly but you might just get lucky.🛠

And btw I havnt had any issues with battery or alternator since i replaced one that i purchased truck with and I've had it almost 5 years now so however the guy before had it rigged is how it still is if there is a bypass of that fused wire.thanks mike

Well I can definatly check them again but the brake light that is not working I've took out and put into other socket that works and it lights up there so pretty sure the brake light issue is something other then bulb but turn signal thing could be havnt messed with it to much since the signals actually work. I'm a firm believer in not fixing things unless broke or could cause serious issues or lots of cash output Haha cuz I have to many broke things to fix to be fixing things that arnt haha and not to mention the lack of time geez is the clock moving faster and faster each day???? Lol jk

You are right. I got this problem before a time or three.
What happened is sometimes the bulb circuit touch inside and power flow through the other circuit this way. Try removing one bulb at a time and see. Might be corrosion behind a bulb too, or touching connection. Try to work systematically, you'll find the problem.
For the brake light, I also suspect the turn signal switch. Take it appart and look inside, might just need a clean up of the contacts.

Good luck!

J. F.

The light bulb thing is mostly for your turn signal light that goes on when you turn on the parking lights.

Sorry for the confusion.

J. F.

So the turn signal switch seems odd to be messing with brake light but electrical stuff usually doesn't make sense . So how do I go about taking the signal switch apart and cleaning it? Is that switch on the steering shaft?

The switch is under the steering wheel.

The brake light switch sends it's power up to the turn signal switch (under the steering wheel) and then back to the rear stop lights. When you activate the left or right turn signal the brake light power is interrupted and the flasher power is directed to that light leaving the other light in the stop mode. So the turn signal switch does have control of the brake lights as well.

Hope this helps,

Mike B

Ok makes sense now why turn switch would effect it. Thanks for the break down there "Mike b". so how do I go about out cleaning the switch like just wipe off dirty connections and put the electrical grease on there? Or are there other ways of going about it that I should be aware of? Thanks mike

And when u say under the steering wheel you mean steering wheel has to come off to get to it correct?

Hy DIY.MechanicMike, if I am remembering correctly the turn signal switch is made of a plastic type material and is not designed to come apart, the switch is probably the same as the one in a pickup and should be available to purchase from any of the restoration parts supply businesses. Yes you must remove the steering wheel to access the turn signal switch. Mark the steering shaft and steering wheel position before you remove the wheel so that it goes back on in the same position, hope that helps.

Signal switch wasn't a problem to get ordered now I'm working on tracking down at least part number for upper steering column bearing for 72 chevy truck. napa couldn't match measurements to any of the bearings they can get, but they sent me to this online parts store h&h classic parts which they told me it was for some reason discontinued and none of there distributors have picked it up but they can get upper steering column bearings for early 50's models which blows my mind, heck there's more 70s models on road today then 50's why wouldn't you remanufactor a bearing for something you'll sell more of ?? But any help on part numbers for 72 chevy truck upper steering column bearing would be great or any other online classic parts warehouse that would have some for the 1972? Thanks mike

Mike,

To insure you get the best coverage and best responses to your NEW questions you should ALWAYS start a new thread. People won't be looking in "lighting issues" for a "steering bushing issue".

Sorry, my books only go to 1967...

Mike B

Hy DIY.MechanicMike, I believe the bearing, steering shaft p/n is 5955201, there is someone on this forum that searches part numbers at GM dealerships for old stock, I hope he sees this. As Mike B said, each new subject should have its own post, you would get more interest in the new subject that way, hope that helps.

Update!!! : brake lights work on both sides now that I got new turn switch. It's not installed yet but I checked by just plugging it in and hitting brakes cuz I still have steering wheel off and column apart to replace upper bearing. Which I found an upper bearing from classicpartsdotcom for the 1972 chevy truck steering column and apparently the upper and lower bearings are the same in these models. I talked to parts help line and they gave me the o.d. of bearing shoulder(1 5/16"), o.d. of bearing cup(1 1/4"), and i.d. of bearing (3/4")and they seemed to be the same size as mine or at least very very close I think the thousandths decimal numbers were off but that's not gonna effect it fitting they assured me so hopefully it's the right fit, they were 16bucks a bearing plus 10 bucks shipping so not to bad when the first few calls I made about it had me worried it was a relic lol.

But the right turn signal indicator on dash is still lighting up when lights are turned on so, gonna fidget with the bulb right now and see if that works it out.

And will start new thread for steering issue , can you copy these sections out to another thread?

Now for the turn signal indicator on dash it still lights up the right one when lights are turned on but when front right turn bulb is removed the light goes out.... I went back and forth a few times removing and plugging in and the old bulb pulled right outta the socket so I put new bulb in thinking maybe that's what it was but nah new bulb made light come back on what else can i try to fix this???? Thanks mike

It's a ground issue on the right side and you're getting feedback from the ungrounded headlight. To test, clamp a battery jumper cable to a clean ground on the engine or neg side of the battery and clamp the other end to a clean spot on the back side of the light housing and see if the issue goes away...if it does then the rusty fenders are no longer giving you a clean path to ground. Run a new ground wire from the frame to a new clean spot on the fender or to the back of the light.

Mike B

So "mike b" you are an "og"!!! Lol hooked ground from battery to light and it lit up and turned the indicator off so can I just run a wire from negative on battery directly to the light socket mounting bolt and that do it or??? And btw my head light appears to be grounded to that bolt on light fixture does that have any effect on this? Thanks mike

Just add a new wire from a clean spot on the frame to the light mounting bolt or follow the existing wires back to a good ground source so it looks nice. It wouldn't hurt to oversize that new ground wire (#10 awg) as there may be more than one light circuit befitting from it.

Other than it looking bad, you can't have to many ground wires...

Mike B

Yeah I was just thinking about taking the ground bar out of an old breaker box and wire that directly from negative terminal and bolt it to frame and just start hooking electrical grounds that become issues to the ports lol. Would this work? Cuz I'm sure there will be future issues as it's getting older and the humidity here in southern illinois ain't giving up lol

You already have a ground bar...the frame!

Make sure the battery ground strap goes to the starter mounting bolt or a bell housing bolt right next to the starter. Then put a second strap from the starter/bell housing to the frame. Now as you find ground issued just connect anywhere out of sight to the frame with a short piece of wire and you're done. Done forget to clean ALL of the contact areas to clean bare metal.

Mike B

Ok so my battery ground goes to one of the head bolt holes on the front part of engine.... is this an ok grounding point or is that shysty? And that is the only ground I think I have so I guess they assumed the engine is mounted to frame so it's all connected.?.?.? Not sure... but if I need to run another ground I will.

But about the turn indicator, is it possible the light socket is bad because I put ground from battery straight to socket mounting bolt and it went away but then a few turn signals later it came back.. and then I jiggled bulb and it came on and indicator glow went out. So I then took bulb out and put wire brush in drill and cleaned the socket thinking there was a connection issue but that didn't do it either so I'm thinking there's a short behind the spring loaded contacts in the socket. Is this possible? And if so how should I go about fixing cuz this is becoming a tedious or deal with to much back and forthing lol

Try this, take the bulb out and using a pair of pliers squeeze the contact(s) creating a small burr on each contact. Then put the bulb back in place. If there is a contact issue this has been known to cure it. Good luck.🛠

Wow that totally worked Haha. thanks for that tip, I'm sure it will be useful in the future... unfortunately.

Finally done with the petty electrical probz!!! Thanks everyone for all the great help.