1990 GMC Sierra Dash Brake light ON

ZIPDADDY

MEMBER
1990 GMC SIERRA
V8
2WD
AUTOMATIC
101,000 MILES

Had front brake job done, including new lines. Next day light comes on. How do I reset switch. Already did computer/battery disconnect to no avail.
Thanks in advance
Zip.

Thursday, May 8th, 2008 AT 10:17 AM

7 Replies

MERLIN2021

MECHANIC
17,250 POSTS

Which light came on? Red brake light? ABS? Both? Or service engine?

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Thursday, May 8th, 2008 AT 2:39 PM

ZIPDADDY

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6 POSTS

The only light on is the red brake light. It is on constantly. I don't believe this truck even has ABS, but not sure. I really think it's the same light that comes on when a brake line "blows", sending the switch to one side or the other. The key is it came on right after front brake lines were replaced.

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Thursday, May 8th, 2008 AT 5:07 PM

MERLIN2021

MECHANIC
17,250 POSTS

Check the fluid level in the master, and check the parking brake lever switch. If they are ok, check for any leaks, and that DOT 3 brake fluid is the only thing that was added! You can tell if the rubber has swelled on the master cyl, cap!

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Friday, May 9th, 2008 AT 2:58 AM

ZIPDADDY

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6 POSTS

PLEASE, are you reading my question thoroughly? I've already checked all the items you've mentioned. No leaks, parking brake switch OK, master full. OH, I have checked and found that the light DOES get slightly brighter when P-brake is applied. Hmmm.
Thanks again
Zip

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Saturday, May 10th, 2008 AT 9:59 AM

MERLIN2021

MECHANIC
17,250 POSTS

If all these where checked, it's possible the proportioning valve is stuck off center, jack up the rear of the truck press brake pedal, do the rear brakes hold? The other thing to do is grab an assistant to help bleed the front calipers, you will need to press and hold the button on the front of the prop valve while you bleed it. Sorry about the confusion!