3rd brake light not working. CHMSL - ZR-1 Net Registry Forums

jad1014 · 08-27-2021

Hello,

My CHMSL are not working. My rear brake tail lights work and hazards work. I unplugged the two connectors going into the stop light switch and the smaller light blue one has no power in the connector. I assume it should have power? Where should I look next? I am afraid i am beyond my threshold with solving electrical issues.

Thanks
Jason

Matt B · 08-27-2021

Brake lights are all in one connector. The other one is to disable the cruise control.

Energy is provided via the center wire whereas the two outer ones route the current to the brake light "clusters" - 4 lower and central high.

Remove the switch (just pull it out towards the inside of the car) and measure the resistances between center and both outer contacts.

If there is an issue open it by carefully prying out the 6 small latches and thoroughly clean the contact points.

Good luck! 20210711_103727.jpg 20210711_103510.jpg 20210711_104120.jpg

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Corvette95 · 08-27-2021

I MAY be wrong, but going from memory, both switches will cause an in/op third brake light. I vote either bad switch or just as likely, all those expensive little bulbs in the lamp are out.

Young1 · 08-27-2021

Go to Napa and get a new switch. Been there done that. I even took the 30 year old apart and cleaned it. It still did not work. Put in a new one and good for another 30 years!

DRM500RUBYZR-1 · 08-27-2021

post 3 and 4 are correct.
It is almost a 50-50 chance that it is one or the other.
Every time we check the switch first, it's all of the bulbs out.
If we check the bulbs first, it is the switch.
Trim limber techs probe the switch first.
The more "executive cut" techs opt to probe the bulb sockets first.
Working under the D/S hush panel can be a contortionists' practice session.

Marty

jad1014 · 08-27-2021

Quote:

Originally Posted by DRM500RUBYZR-1

post 3 and 4 are correct.
It is almost a 50-50 chance that it is one or the other.
Every time we check the switch first, it's all of the bulbs out.
If we check the bulbs first, it is the switch.
Trim limber techs probe the switch first.
The more "executive cut" techs opt to probe the bulb sockets first.
Working under the D/S hush panel can be a contortionists' practice session.

Marty

Thanks to all. It is only one switch to replace, correct? I though the second switch with the unused plug was for cruise control.

Should this connector have power:

jad1014 · 08-28-2021

Hi - i replaced the switch and it didn?t solve the problem. Whats a good way to test for power at the bulb? I put a tester on the sauder back section of the board that holds the four lights, but not sure if that?s a good way. What?s a good source for replacement bulbs?

HAWAIIZR-1 · 08-28-2021

Quote:

Originally Posted by jad1014

Hi - i replaced the switch and it didn?t solve the problem. Whats a good way to test for power at the bulb? I put a tester on the sauder back section of the board that holds the four lights, but not sure if that?s a good way. What?s a good source for replacement bulbs?

Some of us have upgraded to LED strips.

http://www.zr1.net/forum/showthread.php?t=30223

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Matt B · 08-29-2021

Quote:

Originally Posted by jad1014

Whats a good way to test for power at the bulb?

Maybe to open the brake light and measure at the sockets. If you have to replace bulbs you need to open it anyway.
You may also try to measure resistance between the plug and ground. If the circuit is closed (I.e. At least one bulb is okay, circuit board is okay and there is a proper ground) there should be any reading. If there is no reading circuit is broken somewhere. From here I'd open the brake light and check everything inside.

As for the bulbs due to the lack of availability of that US standard on my continent I replaced mine with 8 watts G4 standard socket halogen bulbs. They are a bit larger but squeeze in nicely. These are also available as LED.
Screenshot_20210829-095418_eBay.jpg

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jad1014 · 09-09-2021

I don?t think I have power to the CHMSL bulbs. The SLS switch has been replaced and I found some 891 bulbs and replaced two with no luck. I think that?s about as much as my skill set will offer for this problem. I didn?t bother with the 20A fuse since my hazards work. Any other thoughts? Thanks again.
Jason.

08-27-2021	#1
jad1014 Join Date: Jun 2019 Location: MA Posts: 27	3rd brake light not working. CHMSL Hello, My CHMSL are not working. My rear brake tail lights work and hazards work. I unplugged the two connectors going into the stop light switch and the smaller light blue one has no power in the connector. I assume it should have power? Where should I look next? I am afraid i am beyond my threshold with solving electrical issues. Thanks Jason

08-27-2021	#2
Matt B Join Date: Jan 2021 Location: Beautiful Bavaria Posts: 523	Re: 3rd brake light not working. CHMSL Brake lights are all in one connector. The other one is to disable the cruise control. Energy is provided via the center wire whereas the two outer ones route the current to the brake light "clusters" - 4 lower and central high. Remove the switch (just pull it out towards the inside of the car) and measure the resistances between center and both outer contacts. If there is an issue open it by carefully prying out the 6 small latches and thoroughly clean the contact points. Good luck! 20210711_103727.jpg 20210711_103510.jpg 20210711_104120.jpg Sent from my SM-G991B using ZR-1 Net Registry mobile app __________________ ZR-1 #638/1991 Last edited by Matt B; 08-27-2021 at 06:49 PM.

08-27-2021	#3
Corvette95 Join Date: Jan 2006 Location: Decatur, AL Posts: 1,119	Re: 3rd brake light not working. CHMSL I MAY be wrong, but going from memory, both switches will cause an in/op third brake light. I vote either bad switch or just as likely, all those expensive little bulbs in the lamp are out. __________________ Corvette95 Registry and Forum (*************) 1989 C4 Conv Wht/Gry Auto Hardtop Top Flight SOLD 1995 C4 Coupe Purple/Blk 6 Speed 1989 C4 Conv Wht/Red Auto SOLD 1996 C4 Conv Black/Tan Auto SOLD 1994 C4 Coupe Wht/Blk SOLD 1995 C4 ZR-1 White/Gry #278 Dual Dunn Head SOLD 1986 C4 Coupe Black/Red 4+3 SOLD 1990 C4 ZR-1 Red/Red #0454

08-27-2021	#4
Young1 Join Date: Sep 2016 Location: Ocala, FL Posts: 899	Re: 3rd brake light not working. CHMSL Go to Napa and get a new switch. Been there done that. I even took the 30 year old apart and cleaned it. It still did not work. Put in a new one and good for another 30 years! __________________ Steve Young 1991 ZR-1 Quasar Blue Metallic/Black #729 Second Owner 1991 ZR-1 Dark Red Metallic/Black #2040 SOLD 1990 ZR-1 Dark Red Metallic/Saddle #1670 SOLD Double your happiness.....complain half as much.

08-27-2021	#5
DRM500RUBYZR-1 Join Date: Sep 2008 Location: Mullica Hill, New Jersey Posts: 2,593	Re: 3rd brake light not working. CHMSL post 3 and 4 are correct. It is almost a 50-50 chance that it is one or the other. Every time we check the switch first, it's all of the bulbs out. If we check the bulbs first, it is the switch. Trim limber techs probe the switch first. The more "executive cut" techs opt to probe the bulb sockets first. Working under the D/S hush panel can be a contortionists' practice session. Marty

08-28-2021	#7
jad1014 Join Date: Jun 2019 Location: MA Posts: 27	Re: 3rd brake light not working. CHMSL Hi - i replaced the switch and it didn?t solve the problem. Whats a good way to test for power at the bulb? I put a tester on the sauder back section of the board that holds the four lights, but not sure if that?s a good way. What?s a good source for replacement bulbs?

09-09-2021	#10
jad1014 Join Date: Jun 2019 Location: MA Posts: 27	Re: 3rd brake light not working. CHMSL I don?t think I have power to the CHMSL bulbs. The SLS switch has been replaced and I found some 891 bulbs and replaced two with no luck. I think that?s about as much as my skill set will offer for this problem. I didn?t bother with the 20A fuse since my hazards work. Any other thoughts? Thanks again. Jason.