Headlight switch gone bad?

[dmw319]

So my brake lights work just fine, but when I put my headlights on, the brake lights aren't working anymore. Is the switch the most likely culprit?

[LockDoc]

Originally Posted by dmw319

So my brake lights work just fine, but when I put my headlights on, the brake lights aren't working anymore. Is the switch the most likely culprit?

I would say most likely bad grounds.

http://67-72chevytrucks.com/vboard/s...d.php?t=422234

LockDoc

[dmw319]

Originally Posted by LockDoc

I would say most likely bad grounds.

http://67-72chevytrucks.com/vboard/s...d.php?t=422234

LockDoc

Thanks, I will check these.

[Ol Blue K20]

Originally Posted by LockDoc

I would say most likely bad grounds.

http://67-72chevytrucks.com/vboard/s...d.php?t=422234

LockDoc

X2 on the grounds. I would clean and check them all.

[dmw319]

So bringing back this thread.. it seems that my left brake light is intermittent. Sometimes it works, sometimes it doesn't. This also affects my left blinker. On my instrument cluster the left blinker is sometimes lit up already so my left blinker lights don't function correctly. Then other times it seems to work normally.

Could this still be a grounding issues? I have purchased 3 ground straps and plan to redo them all.

One question I have: are the rear taillights grounded anywhere to the frame? Anyone have a picture of their wiring back there to show me what it should look like?

Thanks!

[Andy4639]

Originally Posted by dmw319

So bringing back this thread.. it seems that my left brake light is intermittent. Sometimes it works, sometimes it doesn't. This also affects my left blinker. On my instrument cluster the left blinker is sometimes lit up already so my left blinker lights don't function correctly. Then other times it seems to work normally.

Could this still be a grounding issues? I have purchased 3 ground straps and plan to redo them all.

One question I have: are the rear taillights grounded anywhere to the frame? Anyone have a picture of their wiring back there to show me what it should look like?

Thanks!

Do you have the cluster grounded? I would add a ground to the cluster while I was checking on the ground issue.
Also check the rear light housing and make sure they are grounded good through the housing screw's.

[dmw319]

Originally Posted by Andy4639

Do you have the cluster grounded? I would add a ground to the cluster while I was checking on the ground issue.
Also check the rear light housing and make sure they are grounded good through the housing screw's.

I assume the cluster has a ground stock? I haven't added anything extra.

fyi here are the lights I have:

[Andy4639]

Originally Posted by dmw319

I assume the cluster has a ground stock? I haven't added anything extra.

fyi here are the lights I have:

It should but that doesn't mean it does! I just went through this with mine. LED's need to be right also. No wires crossed. Regular lights don't care. Also if you put the LED's in front you need flashers for them.

[dmw319]

thanks, just sick of the left blinker not working consistently all the time.

[LockDoc]

Originally Posted by dmw319

So bringing back this thread.. it seems that my left brake light is intermittent. Sometimes it works, sometimes it doesn't. This also affects my left blinker. On my instrument cluster the left blinker is sometimes lit up already so my left blinker lights don't function correctly. Then other times it seems to work normally.

Could this still be a grounding issues? I have purchased 3 ground straps and plan to redo them all.

One question I have: are the rear taillights grounded anywhere to the frame? Anyone have a picture of their wiring back there to show me what it should look like?

Thanks!

Yes it could still be a grounding issue. Did you read through the link I posted earlier? I know it is three pages long but there is good grounding info all the way through it..... The bed should be grounded to the frame and the lights are grounded to the bed.

Originally Posted by dmw319

I assume the cluster has a ground stock? I haven't added anything extra.

The picture below shows where the cluster ground connects to the dash and where the wire connects to the cluster plug.

LockDoc

[dmw319]

Originally Posted by LockDoc

Yes it could still be a grounding issue. Did you read through the link I posted earlier? I know it is three pages long but there is good grounding info all the way through it..... The bed should be grounded to the frame and the lights are grounded to the bed.



The picture below shows where the cluster ground connects to the dash and where the wire connects to the cluster plug.

LockDoc

Yes, I did read the link. That is what prompted me to buy the ground straps, just haven't put them in yet.

Thanks for the pic of the cluster grounding!

Do you happen to have a pic of where the lights are ground to the bed? I have a feeling that may be my missing ground.

[LockDoc]

Originally Posted by dmw319

Yes, I did read the link. That is what prompted me to buy the ground straps, just haven't put them in yet.

Thanks for the pic of the cluster grounding!

Do you happen to have a pic of where the lights are ground to the bed? I have a feeling that may be my missing ground.

No picture, but if memory serves me correctly they ground through the tail light housings and screws, except for the lighted side markers, they have their own ground wire. Make sure the housing is clean where the screws tighten up against the housing on the inside, or go ahead and put ground wires on them.

LockDoc

[dmw319]

Originally Posted by LockDoc

No picture, but if memory serves me correctly they ground through the tail light housings and screws, except for the lighted side markers, they have their own ground wire. Make sure the housing is clean where the screws tighten up against the housing on the inside, or go ahead and put ground wires on them.

LockDoc

thanks. ill have to take some pics of my taillights/wiring and post them here. I don't see any noticeable grounds.

[dmw319]

I rechecked my grounds and everything seems to be correct.

Here is a video of the issue. When I put the lights on, the left blinker only (not the right one) turns part way on. Help!

https://youtu.be/M4c3zyJ_Ijg

[randy500]

No blink is usually a bad bulb. I believe the blink comes from heat build up in the flasher causing the bi-metal to bend, the bad bulb doesn't create enough current flow to heat the bi-metal, hence no flash. Bad bulb or bad ground. Use a test light on the socket to see if it blinks.

The taillight housing grounds through the screws to the bed and the bed to the frame through the bed bolts. That path could be compromised by paint, etc. Also the taillight housing where the bulb goes in has a brass insert and that insert can become corroded between it and the taillight housing which interrupts the ground path. Check with a test light grounded at that location checking power at the bulb pins in the socket. Then check using a good ground to the bulb pins.

Sometimes people install a heavy duty flasher too which prevents a good blink, the heavy duty one is for towing and slows down the flash due to the extra load from the trailer lights. You could try exchanging the 4 way and normal flasher to check that.

[dmw319]

Thanks Randy. What is strange is that it blinks on and off normally if my headlights are off. When the headlights are turned on is when I run into the issue.

[randy500]

Originally Posted by dmw319

Thanks Randy. What is strange is that it blinks on and off normally if my headlights are off. When the headlights are turned on is when I run into the issue.

I forgot about the change with the headlights on, I think the headlights may be getting a false ground through the marker lights. Each headlight has a ground strap about 6 inches away to the core support. Check to see they are both good, the ground path for that circuit is core support to RH inner fender which has a ground strap to the frame. The frame is grounded through the 2 ground straps on the firewall to the engine valve cover, check that too.

No LED bulbs right? Those cause havoc with the flasher.

Check that all bulbs are the same brightness headlights on and off, if one is dimmer it indicates a ground problem or a marginal or bad bulb.

[dmw319]

ok maybe this will help.

this is my what my taillights are plugged into. 2 wires are connected and 1 is cut and not in use. its like this on both sides. any idea what its for?


when i pull back my battery on the passenger side, this is the ground, looks ok to me?


ground on the driver side:


valve cover, driver side. missing a ground clearly, but where should it go into on the firewall?


valve cover, passenger side. also missing a ground, there is a hole in the firewall but its directly behind the center of the engine. what should i do with this side?

[randy500]

I haven't had too many stepsides so not sure on the connector, someone will chime in on that I'm sure, you could check continuity between the cut wire and the taillight housing to see if its the ground.

Headlight ground staps pictured are connected correctly, possibly dirty connection of paint interference.

Valve cover ground straps go to firewall and install with 3/8 head sheetmetal screw.

Check the ground strap under the battery from frame to inner fender.

And ground the engine to the cab, somehow.

[randy500]

Is there a ground strap on the negative battery cable? Usually not I think, so if that is the case the ground path to the lights is through the engine to the transmission to the driveshaft then the rearend through the springs...not a great path.

[dmw319]

Originally Posted by randy500

Check the ground strap under the battery from frame to inner fender.

Any pics on that one? I have a big rusted out section right where you are talking, so that could be my culprit.

[dmw319]

Originally Posted by randy500

Is there a ground strap on the negative battery cable? Usually not I think, so if that is the case the ground path to the lights is through the engine to the transmission to the driveshaft then the rearend through the springs...not a great path.

no, i do not believe there is.

[randy500]

I was gonna say something about that rust fender, I saw it in the picture, the ground strap is probably there, its a little rearward and by the frame, you could make some ground wire with ordinary wire to ground the core support to frame and the engine to the cab. The front turn signal housing can corrode inside too like I described on the taillight housings.

Use a test light like I described from housing to light bulb pins, kind of difficult to do though.

[dmw319]

Originally Posted by randy500

I was gonna say something about that rust fender, I saw it in the picture, the ground strap is probably there, its a little rearward and by the frame, you could make some ground wire with ordinary wire to ground the core support to frame and the engine to the cab. The front turn signal housing can corrode inside too like I described on the taillight housings.

Use a test light like I described from housing to light bulb pins, kind of difficult to do though.

a pic would really help, cause i am 99% sure I do not have a ground strap in the location you are referring to. ill take a pic to show you what i mean

turn signal housings all look good.

[randy500]

The ground strap can be seen from underneath, attaches like the firewall with a 3/8 head sheet metal screw. Then to the frame with a regular bolt.

Turn signal housings can look good but have corrosion in that sleeve insert which the bulb locks into preventing the ground path. I just had to re-do my dodge dart taillights for this corrosion I am talking about, had to remove the bulb connector and put in a new universal one, only had blinkers sometimes if the bulb was in just the right spot, hit a bump then no blinkers.