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Ask Mike S. Your Own Question
Mike S.
Mike S., Mechanic
Category: Car
Satisfied Customers: 7081
Experience:  25+ years experience as an auto mechanic.
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Once I pay answer can I ask another question, will you help

Customer Question

Once I pay for the answer can I ask another question, will you help me until the problem is corrected, no extra cost.
Submitted: 1 year ago.
Category: Car
Expert:  Randall C replied 1 year ago.

Hello, Ja sets up different promos at times, you select which you want so,, with that said? usual is a deposit, then we work the problem, Give and answer then? you accept/rate us then? most important.. even after rating or accepting our answer the post does not close , You can still come back to same post with any followups at no add'l charge so if you decide to proceed? i would need all the question details etc to see if I can help, Let me know, Thanks

Customer: replied 1 year ago.
When I turn the lights on the brake lights doesn't work but with the lights off the brake lights work. I was thinking a relay or maybe a ground problem. What do you think?
Customer: replied 1 year ago.
I checked the 10amp fuse for the brakes and it checks good.
Expert:  Randall C replied 1 year ago.

odd so you are saying with vehicle turned off, keys out all brake lights work ok but they dont work when you turn headlights on? or something different?

Customer: replied 1 year ago.
Key in and running with the headlights on no brake lights, turn headlights off the brake lights work.
Expert:  Randall C replied 1 year ago.

how about just parking lights and,, do NONE of the brake lights work as well as the 3rd high mount brake lights?

Customer: replied 1 year ago.
The lights on the far right and the far left were on, I guess that would be the parking lights. I'll check the 3rd high mount brake lights later when the wife gets home and get back with you. Thanks
Expert:  Randall C replied 1 year ago.

ok

Customer: replied 1 year ago.
Same with the parking lights. Break lights only work when head and parking lights are off.
Expert:  Randall C replied 1 year ago.

this one ? I am unsure of. brake lights use different grounds etc so best I opt out and open the post to the other experts

Expert:  Roy replied 1 year ago.

good afternoon my name is ***** ***** I will assist

the first thing that comes to mind is the bulbs. have they been changed and has any wiring been done? I wonder if the brakes are the dull side and park lights are the bright side of the bulbs

Roy

Customer: replied 1 year ago.
Hey Roy. The bulbs have not been changed recently nor has the wiring. The break lights are not dull, they do not come on when the headlights/parking lights are on when the break pedal is depressed. Can you help?
Expert:  Roy replied 1 year ago.

just to check, remove the socket and bulb assembly and have someone work the lights for you and see if the other filament comes on with the brake lights when the parks are on

Roy

Customer: replied 1 year ago.
They don't come on, I also moved the ground wires around to see if it made any difference, no difference.
Expert:  Roy replied 1 year ago.

ok, without being there and testing my self, I cannot continue on this forum. I will open it up to the other guys to see if they have any ideas

Roy

Expert:  Mike S. replied 1 year ago.

I am surprised no one has given you a wiring diagram as of yet. Here is it,

The taillight and the brake lights share the same ground, so a ground wouldn't be the issue.

The stop and taillights also share the same feed wire, so that wouldn't be it either up to the b4 splice.

You could possibly have a shorted relay so, remove the tail relay and/or the tail fuse to eliminate that taillight circuit for right now, then turn the headlights on park and press the brake pedal and let me know if the brake lights work now.

Customer: replied 1 year ago.
I removed the tail fuse then turned the headlights on park and pressed the brake pedal and the brake lights came on.👍
Expert:  Mike S. replied 1 year ago.

try a new tail relay.

Customer: replied 1 year ago.
Where is the tail relay located?
Expert:  Mike S. replied 1 year ago.

Drivers side junction box, the same box that fuse was.

Customer: replied 1 year ago.
Ok thanks
Expert:  Mike S. replied 1 year ago.

If that fixes it don't forget to rate me well, if it doesn't fix it let me know so we can continue.

Customer: replied 1 year ago.
I'm trying to find the location of the relay
Expert:  Mike S. replied 1 year ago.

Drivers side junction box, the same box that fuse was.

Do you still have an owners manual?

Customer: replied 1 year ago.
I found the relay trying to get new relay. When I get it I will let you know if it solves the problem.
Expert:  Mike S. replied 1 year ago.

ok

Customer: replied 1 year ago.
Bad news, put new relay in but it still doing the same thing. I noticed that the relay is hot to the touch.
Expert:  Mike S. replied 1 year ago.

There is a short in the tail lamp circuit. Try leaving that tail fuse out and feel if that relay still gets hot.

Customer: replied 1 year ago.
Ok
Customer: replied 1 year ago.
It doesn't get hot
Customer: replied 1 year ago.
You would think that a fuse would be blown if there was a short.
Expert:  Mike S. replied 1 year ago.

What amp fuse is in it? It's supposed to be a 15 amp.

Anyhow, stick an ammeter in that fuse's socket and measure the amperage while the relay is back in and see what is going on. You will have to turn the light switch on. Make sure that isn't a harbor freight fuse cause GM had a tsb out on their fuses saying they could short them fuses out across the battery and they still wouldn't blow. Just put in a new 15a fuse after checking the ammeter draw.

Then if the ammeter draw is over 15 amps, pull both front parking light bulbs one at a time and read the ammeter after removing each bulb. Then start disconnecting or removing each bulb listed at the bottom of that wiring diagram where C comes in, starting with the stop fuse, then the license bulbs and checking the ammeter after removing or disconnecting each one.