Short Version of My Question:

Is there a brake light failure relay in the '97 850 wagon (non-turbo)? If so, where is it and what does it look like?

Longer Version of My Question:

All three brake lights do not work at all. They have enough volts (though the passenger-side light has twice the volts the other two register).

I checked for and found continuity at the brake switch just above the brake pedal.

A bunch of previous posts claim that the brake light failure relay is often the problem . I can't find the relay on the 97 850 wagon. I can't even find a replacement part on the volvo parts websites.

So, I am wondering if such a relay exists for the 97 850 wagon. If so, where is it and what does it look like?

Any other possible causes for the brake lights not working?

Thanks in advance,

Red

 

I will be honest, I have not heard of this relay that you are talking about. Normally, when all three lights are out, it is because the brake light switch is bad. When you said you have power to the switch, do you know if it is making it's way through the switch to the rear?

 

Thanks for your reply, Andrew.

The part and the post I am referring to are linked below.

Here are the tests that I did to see if the power is getting to the brake lights. If I can do another test or I missed something, please let me know.

1. Found continuity in the brake switch when it is unplugged.
2. Found continuity in the wire that plugs into the brake switch.
3. With everything attached, found volts at each of the wires that plug into the three brake lights.

Am I missing any tests?



The part I am referring to is http://auto-parts.fcpgroton.com/brak...ct_type-Relays

This is referred to as the solution in the following post:

https://volvoforums.com/forum/showth...ke+light+relay


I just saw another post with my same problem but in the sedan. I will look to see if the wagon has this same blue box. https://volvoforums.com/forum/showth...ke+light+relay

 

Ok, it is the brake light switch after all.

I found the blue box. It is the relay switch as indicated on the box itself. You can open it by prying off the back cover with a flathead screwdriver. But, you don't need to open it up to test for continuity. Use your multimeter on 54 and 54R first and then 54 and 54L next to make sure you are getting 10 to 12 volts. Mine tested fine.

Based on Andrew's suggestion, I went back to the brake light switch. Got it to work intermittently. Opened up the switch and saw one of four terminals blackened/corroded. Be careful though, in opening up the switch I broke its casing. Mine still works intermittently even though I cleaned the terminals. So, I need to get another switch anyway.

Also, one person in this forum suggested these switches can get sticky mechanically. WD40 worked for him.