Rear brake light question
05-07-2016, 06:35 PM
#1
Drifting
Thread Starter
Rear brake light question
Hi
I was wondering when the rear brakes are applied does only the
Center High Mount Stop Light (CHMSL) light up? Or should the 4 rear lamps light up as well? This is a 1991 zr-1. Only my CHMSL lights up.
thanks
todd
I was wondering when the rear brakes are applied does only the
Center High Mount Stop Light (CHMSL) light up? Or should the 4 rear lamps light up as well? This is a 1991 zr-1. Only my CHMSL lights up.
thanks
todd
05-07-2016, 06:42 PM
#2
Have you in the past had EXPORT lamps on the car?
Connector at the SLS is likely. If the CHMSL is working the SLS signal is reaching the ABS circuit which the CHMSL is a splice off of. Blue at the SLS is ABS/CHMSL - white is the feed to the directional switch.
Last edited by WVZR-1; 05-07-2016 at 06:52 PM.
05-07-2016, 06:58 PM
#3
Drifting
Thread Starter
The CHMSL is controlled by a wire from the ABS to the light. The four in the cover are from the SLS through the directional switch.
Have you in the past had EXPORT lamps on the car?
Connector at the SLS is likely. If the CHMSL is working the SLS signal is reaching the ABS circuit which the CHMSL is a splice off of. Blue at the SLS is ABS/CHMSL - white is the feed to the directional switch.
Have you in the past had EXPORT lamps on the car?
Connector at the SLS is likely. If the CHMSL is working the SLS signal is reaching the ABS circuit which the CHMSL is a splice off of. Blue at the SLS is ABS/CHMSL - white is the feed to the directional switch.
The 4 rectangular lights work when the directionals are on, and the CHMSL only goes on when the brakes are applied so I guess I am good.I just thought the rectangular lamps turned on as well when the brakes were applied.
Thanks for the help
05-07-2016, 07:06 PM
#4
You should have 5 red stop lights when the brake is depressed, 4 in the bumper and the CHMSL - you DO HAVE ISSUES I'd say and it's likely just the connector at the SLS - unless you've EXPORT lamps and then it's not wired correctly.
Last edited by WVZR-1; 05-07-2016 at 07:12 PM.
05-07-2016, 07:13 PM
#5
Drifting
Thread Starter
thanks
todd
Last edited by 91vettezr1; 05-07-2016 at 07:27 PM.
05-07-2016, 11:35 PM
#7
Melting Slicks
05-08-2016, 01:44 PM
#8
Drifting
Thread Starter
Got under there and the stop lamp switch works the CHMSL but not the 4 rectangular lamps. I am going to replace the switch and see what happens. I also noticed another switch next to Stop Lamp switch,(vacuum release switch for cruise.) There is a vacuum hose connected to it and the end has a 2 prong elect connector but nothing was connected to it.Cruise worked last time i drove the car( 6 months ago)Does the switch have a wire connected to it? I looked everywhere under the dash but saw no loose wire.
thanks
todd
Last edited by 91vettezr1; 05-08-2016 at 02:06 PM.
05-08-2016, 03:32 PM
#9
White wire from SLS to the directional harness right side of column.
05-09-2016, 01:35 AM
#10
Team Owner
Do your Hazard lights work? All 4 rear lights? I looked in my '91 Chevy Corvette Electrical service manual and the Hazard switch feeds the same line that the white brake light wire does. If the Hazards work, it seems the problem has to be in the brake switch from where the white wire comes from
Last edited by ZR-71; 05-09-2016 at 01:36 AM.
05-09-2016, 11:22 AM
#11
Drifting
Thread Starter
Do your Hazard lights work? All 4 rear lights? I looked in my '91 Chevy Corvette Electrical service manual and the Hazard switch feeds the same line that the white brake light wire does. If the Hazards work, it seems the problem has to be in the brake switch from where the white wire comes from
Just checked and hazards do work. I should have the new brake switch installed later this week. I will let you know the results.
thanks
05-09-2016, 11:49 AM
#12
Hazards and stop only share a fuse and since you have CHMSL the HAZARDS are known to be powered and that only confirms it's NOT a fuse issue. SLS is certainly the go to for a solution but I would think confirmation of the WHITE to the A terminal of the SLS is a first maybe and to 17 of the directional switch next.
You can attach the connector to the new SLS and check while in your hand. If it works in your hand it should work installed. If you don't have 5 stops in your hand you won't have 5 in the car.
You can attach the connector to the new SLS and check while in your hand. If it works in your hand it should work installed. If you don't have 5 stops in your hand you won't have 5 in the car.
05-11-2016, 10:23 AM
#13
Advanced
On our 90 the CHMSL had stopped working last year and I changed the SLS to a new one.
it has a plunger on it that has to "be set" after the install as to when the CHMSL lights and also when the four in the back will light.
as I was doing this I could get the CHMSL to light and than it took about another 1/2" of movement to light the other four. I adjusted it and it works fine.
now, if your breaks come up on a "hard pedal" just after the CHMSL lights and you get little or no movement on the pedal, it will not light the four in the back......adjust your SLS and see if they light or press real hard on the pedal and see if they light.
today, if I Press the pedal just the right amount I will get only the CHMSL to light and than just about 1/8" more press and the four will also come on.
In normal use they all come on at the same time, I have to try real hard to only have the CHMLS come on only. I can only do this when it is parked and look in a mirror it see it.
Dean Nelson
it has a plunger on it that has to "be set" after the install as to when the CHMSL lights and also when the four in the back will light.
as I was doing this I could get the CHMSL to light and than it took about another 1/2" of movement to light the other four. I adjusted it and it works fine.
now, if your breaks come up on a "hard pedal" just after the CHMSL lights and you get little or no movement on the pedal, it will not light the four in the back......adjust your SLS and see if they light or press real hard on the pedal and see if they light.
today, if I Press the pedal just the right amount I will get only the CHMSL to light and than just about 1/8" more press and the four will also come on.
In normal use they all come on at the same time, I have to try real hard to only have the CHMLS come on only. I can only do this when it is parked and look in a mirror it see it.
Dean Nelson
05-14-2016, 12:05 PM
#14
Drifting
Thread Starter
On our 90 the CHMSL had stopped working last year and I changed the SLS to a new one.
it has a plunger on it that has to "be set" after the install as to when the CHMSL lights and also when the four in the back will light.
as I was doing this I could get the CHMSL to light and than it took about another 1/2" of movement to light the other four. I adjusted it and it works fine.
now, if your breaks come up on a "hard pedal" just after the CHMSL lights and you get little or no movement on the pedal, it will not light the four in the back......adjust your SLS and see if they light or press real hard on the pedal and see if they light.
today, if I Press the pedal just the right amount I will get only the CHMSL to light and than just about 1/8" more press and the four will also come on.
In normal use they all come on at the same time, I have to try real hard to only have the CHMLS come on only. I can only do this when it is parked and look in a mirror it see it.
Dean Nelson
it has a plunger on it that has to "be set" after the install as to when the CHMSL lights and also when the four in the back will light.
as I was doing this I could get the CHMSL to light and than it took about another 1/2" of movement to light the other four. I adjusted it and it works fine.
now, if your breaks come up on a "hard pedal" just after the CHMSL lights and you get little or no movement on the pedal, it will not light the four in the back......adjust your SLS and see if they light or press real hard on the pedal and see if they light.
today, if I Press the pedal just the right amount I will get only the CHMSL to light and than just about 1/8" more press and the four will also come on.
In normal use they all come on at the same time, I have to try real hard to only have the CHMLS come on only. I can only do this when it is parked and look in a mirror it see it.
Dean Nelson
todd
Last edited by 91vettezr1; 05-14-2016 at 12:06 PM.