You may have a intermittent grounding problem "somewhere" in a lighting circuit. "Maybe" door switch or either door...but could be anything

FWIW my 67 came with main battery cable to block with an aux (smaller wire to PS fender. Copper straps from each VC to firewall and strap from body to subframe, PS

IIRC the white wire on door switch is white and I believe the ground and the + wire feeding the sail panel and other interior lights is orange. Apologies if its opposite but use a DVM and start probing.

LED or any light will have issues if there is a circuit problem, grounding or + source.

Regarding "brightness" of any lights, headlights or interior, a headlight relay harness will make them all brighter as it removes the full 12v load off the headlight switch. I got mine from Speedway but other vendors likely have them. Plug & play, no cutting any stock wires. It won't resolve your grounding or + power issue but is a significant improvement, especially the headlights.

 

You may have a intermittent grounding problem "somewhere" in a lighting circuit. "Maybe" door switch or either door...but could be anything

FWIW my 67 came with main battery cable to block with an aux (smaller wire to PS fender. Copper straps from each VC to firewall and strap from body to subframe, PS

IIRC the white wire on door switch is white and I believe the ground and the + wire feeding the sail panel and other interior lights is orange. Apologies if its opposite but use a DVM and start probing.

LED or any light will have issues if there is a circuit problem, grounding or + source.

Regarding "brightness" of any lights, headlights or interior, a headlight relay harness will make them all brighter as it removes the full 12v load off the headlight switch. I got mine from Speedway but other vendors likely have them. Plug & play, no cutting any stock wires. It won't resolve your grounding or + power issue but is a significant improvement, especially the headlights.

I am not good with electrical but will add body to subframe strap and VC to firewall straps. From what I've read you can't have too many grounding points on these cars. I do have a DVM that a friend gave me many years ago when he got a newer model. The only thing I use it for is checking my vehicles battery voltage. I really don't know how to use it. So if I start with the door switches, do I pull the kick panels off and probe them with the car running or not? Thanks in advance for your help.

 

I noticed the sail panel lights dimmed in sequence with turn signals or 4-way flashers. This occurs when engine is not running. This also happens when it's running, but with no flashers turned on all interior and exterior running lights are flickering a little bit. This has been going on for as long as I've had the car.

I wanted to add LED lights on the rear only and from what I've been reading they won't work if you have a grounding problem.

Any help would be greatly appreciated and here's what I have done or checked so far.

Negative batt cable is running straight to block. I added a braided strap from block to frame and another wire from battery(-) to fender. Where else do I need to check or add grounding?

Do you have a smaller redundant negative cable on the battery cable to ground?

 

I do not. I just have the 2 smaller wires. 1 to fender and the other runs through the firewall with the aftermarket ac hoses and vacuum line. What size should the smaller redundant cable be and where to ground it?

 

the door switches just unscrew. Just open door and they are on the A pillar lower part about midway of door. The one wire going to them if you just touch to body or any ground, the interior lights come on. When you put it back with the wire on, rotate it about 5-6 times counterclockwise as screwing it in will otherwise wind the wire up into a coil if you don't. Those switches are cheap to replace but IDK if that is your problem

Your dash light switch also just may be worn and needing replacement

The continuity function will work on meter if you disconnect battery and whatever wire you probe to ground it will beep. It looks like on your meter that is the arrow+ symbol. Just set it to that and touch the two meter ends together, it should beep as a test.

There is one member who is very knowledgeable at wiring (Nova??) so ideally he can jump in with 411

 

Great,thanks a lot. That would be much easier than taking the panel off. I'll give those a check.

PO replaced the light switch in 2020. I do realize it could still be bad.

 

I noticed driver side SP light is much brighter than PS. I know it could just be the bulb, but I can't get the covers off to check. They look original so probably fragile. How exactly do they come off?

 

if your referring to tail lights, the bulbs just come out with socket from inside trunk. One side being dimmer is often bad ground from socket to housing. Get a AAW socket and pigtail and replace. Around $14. Do not buy the $5 one from auto part store.

 

While I'm working on these issues I also noticed my voltage regulator does not have a condenser attached to it like I was reading in an older post. They were talking about a 68 though. Is the 67 suppose to have one? I just have a ground running from the VR to the ground where the headlight is grounded.

I was actually referring to the sail panel covers. They feel awful tight and I'm afraid of breaking them. Do they twist or just pull off?

 

You do need more than just the one large cable ground between the battery negative post and the engine. This main large cable is basically needed for the starter and alternator mounted to the engine but your other things on the car rely on a chassis ground and since your motor and transmission are probably on rubber mounts, then there is no good electrical connection to things grounded to the body of the car. You can get a ground path from the engine and transmission to the body of the car but this can happen through shifter linkages or through the bearings in the transmission which then connects to the driveshaft, rear axle and such and then a electrical connection can be made from the rear axle assembly to the body of the car through the emergency brake cables but is is not the best electrical path.

If you have dedicated grounds from the battery negative to the firewall and/or a ground from the engine to the firewall, this should be better.

Also too, think about the main power getting into the car through a single power wire. If the turn signals flash on and off they may be working just fine but may be getting some voltage drops on that circuit that you do not see and then if the domelight is turned on with the flashers going on and off, the dome lights might see at one point 13.0V and then when the flasher turn off the voltage rises to let's say 13.2V and then they dim once again as the lights are only getting 13.0V when the flashers are on and lit up and you see the flickering.

Jim

 

Thank you!
I am working on getting a couple more grounds added, but just to make sure for now about the dimming.
The dimming occurs on all lights (inside and out) when I turn on 4-ways or TS's. It's the same whether the engine is running or not. Headlights are the only ones I don't notice the dimming.

 

@Rjames40 In your other thread about turn signals you mentioned you have a Dakota Digital dash. How did you ground the DD unit? I would suggest grounding it to the engine block or possibly directly to the battery. If you've already done this then disregard my suggestion.

 

I really do appreciate all the suggestions to look at how things are done by me and PO. On DD unit I do not have the ground running to the block or battery. I will get that on the list along with the other grounding wires I need to run.

I do need to mention that the TS issue with the lights dimming has probably been going on ever since I've owned the car and I didn't realize it. The reason I'm saying this is because I've never had the door open while checking the TS bulbs. I've always started the car and reached through the window, so the interior lights wouldn't have been on for me to notice the dimming. It was just recently when I had the door open going through all the sensors and functions of the DD unit making sure everything was working when I noticed the interior lights dimming. I think I mentioned this before but the lights have always had a slight flickering when the car was running and no signal switches were on.

I'm sorry if this is a little long but I remember seeing someone being told to enter as much as possible about your problem so the guys here can help better diagnose.

Rick

 

Your DD instrument cluster does not need to ground to engine or - battery directly, just to some ground under dash. However, your body does need to be grounded to engine and frame. - Battery cable to engine block and PS fender

As a test just take a clip lead and attach it to some metal part of your DD cluster and clip the other end to some ground location under dash to see if that resolves your issue (assuming you do have all engine, frame and body ground cable/straps on)

 

The Dakota Digital dash has a control box that must have a good ground for proper operation. The best ground available generally is the engine block due to the battery negative terminal being connected to the block. Look up any of the DD wiring instructions for further explanation.

 

The courtesy light's white wire is the ground. It is connected to the sail panel lights, the roof light and the lights under the dash. It also goes to the headlight switch. Ultimately, it goes to the door switches to complete the ground path.

When the door is opened the little door switch makes the connection to ground. This completes the circuit and the lights come on. If you remove the switch, it is not going it illuminate the lights because it is no longer connected to ground. Sometimes the switches get rusty and no longer make a good connection to ground.

Turn your headlight switch to light up the courtesy lights. Then turn on your blinkers. Do they still go dim?

Over time, the light sockets get hot and burn the contacts. You might have a poor connection between the socket and the bulb.

 

Ok, here's what I have done today.

Battery to block ground is good. Battery to PS fender and braided strap from block to frame good. I added a braided strap from frame to firewall. I ran a temporary ground from Dakota D gauges strait to Battery.

I still need to check door switches and SP lights.

I did find something interesting today that I was unaware of. The lights are still flickering when the car is running because I was watching close to see if some of this work paid off. They did not start flickering for a few seconds until after the car was running. I thought that was odd so I tried this 5 more times. I turned on running lights and a TS and then started the car. I timed 7 to 9 seconds before they started flickering.?

 

I did find something interesting today that I was unaware of. The lights are still flickering when the car is running because I was watching close to see if some of this work paid off. They did not start flickering for a few seconds until after the car was running. I thought that was odd so I tried this 5 more times. I turned on running lights and a TS and then started the car. I timed 7 to 9 seconds before they started flickering.?

What alternator do you have ?

If it's an original style with the external regulator, unplug the regulator with the engine off, then start the car and see if the same thing happens after 7-9 seconds like what you noticed before.

OR

If it's a newer internally regulated alternator, then with the motor off, unplug the 2 wire connector on the alternator then start the car and see if the same thing happens after 7-9 seconds like what you noticed before.

OR

If you have a 1 wire alternator, disconnect the battery and then take off the cable on the output post of the alternator, tape it off so it cannot short to ground then reconnect the battery, start the car and then see if the same thing happens after 7-9 seconds like what you noticed before.

After or between doing any tests with the alternator not producing output, maybe hit the battery for a bit with a charger to keep it's voltage up but do not do the tests with the charger connected to the car so you do not create some other added issue(s).

If the alternator is kicking in and out and producing a higher voltage then a lower one quickly, then this would get the lights to flicker up and down in brightness.

Jim

 

Door switches are ok. I have the SP lights out and they appear to be ok, but I may add the redundant grounds like someone recommended. I need to go back through the thread and find who that was because I don't know where a good place to add them would be.

There is a TS 90 on one side and a GE 1004 on the other. After searching online most bulbs for a 67 show only 1 contact point and crossing them at the auto parts stores close to me, they crossed to a single contact bulb.

What are you guys using?

 

I would start with the front park/turn lights and make sure their ground wire have a good ground connection and tightly screwed to the core support.

If this doesn't solve it, use jumper wires with alligator clips to ground the rear lights.

Hopefully one of these sets of mproved groundings will give you the asnwer.

 

If for any reason you change your VR, consider a solid-state version like Tuff Stuff. Made in USA. Amazon

 

I may get a SS VR just to put on the shelf. And then re-check grounds on parking lights and tail lights with a separate ground. I will then work on Jim's suggested tests. This may take some time, but I'm determined to figure this out, as long as I have help from you guys.

 

IDK if OP's VR is his core problem but only suggested to consider a solid state one if replacing it. For me, my original type was failing output at idle and also subsequently my stock 3 wire ALT went bad with the low glow GEN light on at idle

I have HEI (Pertronix module in stock distributor) and have read HEI is happier with a SS VR. For me, it has not been any problem since install. I prefer USA made products and have found Tuff Stuff products have worked very well for me.

My 3 wire ALT is just an AC Delco I bought from Summit, 35 amp. I don't have any heavy amp load draws added (EL Fans, big stereo, etc)

Solid wiring connections and grounds are critical to and need to be solid or gremlins will show their faces

 

I am learning so much here I don't know if my ol brain can handle it, but anyway I have some good news. I re-checked grounds on parking lights and rear lights. Drivers side PL housing has a stud broke off and assembly it looks like Gorilla glue or epoxy holding it in. Light and TS working so I just added a redundant ground for now.

Took rear light assemblies out and cleaned all lights, sockets and everywhere assembly comes in contact with the car. Put it all back together without the exterior sealing gaskets because there wasn't any when I took it apart. Started car and didn't notice any light flickering at idle. Turned on all lights and still no flickering until I turned on TS or 4- ways. They still dim in sequence with the flasher, but not as bad.

I did run the 2 wires directly back to the tail light assemblies from battery and didn't notice any difference.

O well, on to the positive wires like Jim suggested. I downloaded the manual on the Fluke meter, but haven't had a chance to look at yet.

Again I thank you all for the help.

Rick

 

I am learning so much here I don't know if my ol brain can handle it.

I downloaded the manual on the Fluke meter, but haven't had a chance to look at yet.

Again I thank you all for the help.

Rick

I used the peak hold feature on my fluke years ago as I had a customer that after I put a new radio in his car he was driving down the road and just the audio cut out. The display stayed lit and worked fine.

I put my meter on the battery and only so often when the engine was revved the meter then caught a peak voltage of 18V. The radio's audio was going into protect from too much voltage but the display we guess just didn't care.

He put on a new alternator and the audio issues went away.

The meter should also be able to measure the lowest voltage when things like the starter is turning over the motor.

Jim

 

As I started on the positive wire testing I thought I would remove the wrap and the electrical tape on the outside to get familiar with some of the wire colors and see what others have done.

A wire terminated with a wire nut on it. It's hot and testing the same as the battery. Looks like the only place it could have reached is the horn rely.

And then there's this.

5 wires. 1 to horn relay(left side), 1 to VR, 1 to alternator, 1 to wire that's terminated w/wire nut and 1 that runs in the harness going behind the rad support and appears to run over to PS.

The large red wire coming from the firewall runs to the right side of horn relay.

Keeping in mind this is an rs with headlight doors and motors, but no motors are there. I'm guessing that's what all the plugs are for.

There is also a large red wire on the positive battery connection (PS) that runs down to the headlight bucket area and then across the radiator support to DS.

Not sure if any of this is causing my issue, but wanted to keep getting as much info posted as I run across it.

Again, much appreciated for the help.

Rick

 

As I started on the positive wire testing I thought I would remove the wrap and the electrical tape on the outside to get familiar with some of the wire colors and see what others have done.

View attachment 328529

A wire terminated with a wire nut on it. It's hot and testing the same as the battery. Looks like the only place it could have reached is the horn rely.

And then there's this.

View attachment 328531

5 wires. 1 to horn relay(left side), 1 to VR, 1 to alternator, 1 to wire that's terminated w/wire nut and 1 that runs in the harness going behind the rad support and appears to run over to PS.

The large red wire coming from the firewall runs to the right side of horn relay.

View attachment 328532

Keeping in mind this is an rs with headlight doors and motors, but no motors are there. I'm guessing that's what all the plugs are for.

There is also a large red wire on the positive battery connection (PS) that runs down to the headlight bucket area and then across the radiator support to DS.

Not sure if any of this is causing my issue, but wanted to keep getting as much info posted as I run across it.

Again, much appreciated for the help.

Rick

Yep, you will just have to see what is up.

Buried connections with wire nus are not a good thing.

Your picture (and while not super clear so maybe check your camera settings) of what looks like 10 gauge wires all being connected together with a crimp terminal and soldered probably is factory.

This is a main charge wire connection I took out of a 66/67 Chevelle and IS factory:

This connection is what the guy from mad website talks about as being a "splice".

Jim

 

Did you notice some of my meter readings on Post #36? It's right after your Post #27.

 

that splice in the picture above is original to the car or I should say GM crimp solder splice

 

Yes, my splice looks just like that. The only difference is mine has five 10ga wires with 1 of them terminated with a wire nut put on it. Like to know where it's suppose to go, but everything is working (at the moment) so I'm focusing on the lights dimming.

Thank you for the reply. Every little bit is helpful.

Rick

 

Jim, I have the 10ga wire made up to run from the battery to the fuse panel inside. I also have one to run the negative if more readings are done.

Keeping in mind that I'm not real sure about what I'm doing on this electrical, I need to ask a question before I start this.

If I run a 10ga (fused 30amp) wire to check these, is there a possibility I could be "back- feeding" the smaller wires and potentially do some damage?

Also, do I start the car and apply the load before or after I connect the wire?

Thank you

Rick

 

If everything is basically working on the car and not blowing any fuses or fusible links, if I were to take a 10 gauge test wire with a 30A fuse at the battery and run it to let's say the POWER side of the dome light fuse I should be fine.

Be aware that on the dome light fuse, one clip of the fuse goes to the battery and the other to the dome light circuit and a way to check this is to take the fuse out and one side will show power which is getting power from the battery and the other side will be dead which that side goes out to the dome light.

If it was me and if I then were to make this connection off of my test wire to the fuse blocks dome light fuse the voltage measurement at this spot on the fuse block will either be the same as it was before OR it would increased (it cannot decrease). NOW if the dome light is NOT on, chances are the readings WILL be the same as you are not drawing any power so make sure the dome light is on and illuminating things.

If I show a significant increase, then this tells me there is an issue with the original/old wiring and I have voltage drops on that side.

If it is real close between the original wiring and then with this test wiring addition, then we need to progress further into the circuits.

Maybe too do a before and after voltage tests with the ignition switch in the run position and then when the signals are on and off.

Jim

 

I went back to some basics after reading a lot of older posts.

I went through and removed all grounding points that I know about and cleaned them down to bare metal.

I read where the alternator case should have a ground run to the radiator support. Mine does not and there is a terminal stud marked Ground. Do I need that grounded? I ran a temporary ground to the Rad support and no change.

Cleaned terminals on horn relay even though horns were working. Cleaned ground wire from VR to radiator support. I do not have the condenser.

I cleaned the terminals on the fuse panel as good as possible without removing it. Replaced with 2 new fuses in the tail and hazards only.

Not sure what else to check. I know there's power running to the headlight switch at all times and even if I don't pull the switch out, still have dimming. Could the switch be bad and causing this?

Thanks in advance for your help.

Rick

 

Rotate the rheostat many times without power. You may have some oxidation on the resistor. Any oxidation will decrease voltage to instrument lights and sail panel lights. Minor voltage flucuations in the charging and car electrical systems will show up in the lights first.

Here is a photo of the switch and rheostat. It should help you understand why the rheostat will get oxidation after many years. The wiper copper contact and the exposed wire wound resister are exposed to the cabin elements all the time. High humidity will cause the oxidation over time.

If you can't get the switch to improve, find a good switch. A NOS switch could be good only if stored in a climate controlled storage area. Little chance to find people storing parts in heated/ air conditioned warehouses or garages. Here is one for the hidden headlights. Bit expensive, but better than china junk.

ACDelco Switch D1588 Searchfor this number when you decide to find a new one. Still made in China now. But still better than low dollar parts by unknown vendors coming from china.

 

That’s a good place for no-ox on a q-tip