2003 Volvo V70 High mount brake light

Googs1080 · Post by **Googs1080** » 07 Mar 2015, 14:28

Hi all,

The high mount brake comes on every 10 seconds. it lasts for just a second then will go back off until 10 secs later. The high mount light will not come on when the brake is pressed. The top rectangle thing in the rear fuse compartment clicks with the light. I swapped out that one with another one. The other one clicks every 10 seconds as well. Anyone have any ideas where to look or what is happening here? The left and right brake lights work fine.

draser · Post by **draser** » 09 Mar 2015, 13:04

I'd unplug the harness going to it, and see if the relay clicking stops. If it stops then the high brake light is the problem.

Sardine · Post by **Sardine** » 09 Mar 2015, 17:53

... see if the relay clicking stops ...

The clicking will most likely stop since the power input (via 10/19:1 has been removed.)
A better test is to a) Unplug the harness; b) Feed +12V to 10/19:1 via a resistor of some value, and 0V to 10/19:5; and c) Observe the output.
If the High light is on then 10/19 is OK. If it turns on then off as before etc. then it's not OK.
Since I don't know what's inside 10/19 I can't tell you what kind of input it expects. I would start at say 24Ohm to get 1/2 amp into 10/19 and reduce the value if I the light does not turn on. It may well expect a raw +12V and limit the current internally somehow.
By the way, are you sure the clicking sound comes from 10/19 (High light.)? It could be coming from the REM.

Googs1080 · Post by **Googs1080** » 10 Mar 2015, 13:03

The clicking is coming from the REM (#5 relay), not the high mounted light. The #5 relay clicks even with the light removed from the harness. It clicks when I replace #5 with another relay as well so I am thinking what ever is sending a signal to #5 relay might be where my problem lays. Not sure how the overall REM logic or construct is, but could a master relay on or to the REM be on its way out and passing a cyclical current which #5 is bearing the brunt of? I ask because there is another relay just to the right and above where #5 is and that one feels warm to the touch where as the others have no noticeable temperatures.

Sardine · Post by **Sardine** » 10 Mar 2015, 14:02

I'm not sure what REM (#5 relay) is. Have you seen my post on the old thread, the one before draser's post?
If you could tell me what REM (#5 relay) is, I can have another look for you.

Googs1080 · Post by **Googs1080** » 10 Mar 2015, 14:52

Your reply about feeding 12+v to 10/19:1? I see that but not sure what the means. Unplug the high light harness and then add power to it and see what happens is my read of it yes? I don't understand what 10/19:1 is in real world. Is there a panel that these are all plugged into? sorry I am very inexperienced at this detailed stuff. If oyu can tell me how to get to 10/19:1 I will certainyl test as you stated.

I added a picture of what my REM looks like and relay #5 that is clicking if that helps. I have another high light and relay #5 clicks as well with that new one connected. So relay #5 clicks with a light attach or without a light. it clicks if I put a new relay in the #5 slot. It clicks if I install a new high mount light.

Googs1080 · Post by **Googs1080** » 10 Mar 2015, 15:32

Sardine, i found the other post you referred to. I agree, seems needless Volvo split these up. I will try and study the diagrams to figure out where these pins actually are so I can try and move them as suggested to see if 10/19 is the culprit. if hooking it to 2/79 works then I will keep it there. lol

Sardine · Post by **Sardine** » 10 Mar 2015, 15:56

Those two relays are:
1) Warm relay: RMI13, i.e. 2/72, "Relay, rear window wiper."
2) What you call REM (#5 relay): RMI16, i.e. 2/16, "Relay, itermittent rear window wiping on/off."
This data is from page 26 of the wiring diagram.

These relays have nothing to do with brake lights. I think somehow you have a cross connection between the wiper circuitry and the "High Mount Brake Light." There is some post about cross connection due to broken wires in the rear of V70 sometime ago. Look for that post to work out how to fix your problem.
By the way, if your wiper is on then turn it off and see if the "High Mount Brake Light" stopped blinking.

Googs1080 · Post by **Googs1080** » 10 Mar 2015, 18:39

Sardine, you are spot on! That was the problem alright. I feel dumb not thinking about the intermittent cycle and connecting the problem to the wiper. The high mount is operating off the rear wiper! I turned the wiper off and the clicking and light stopped. I will check the older posts for going after where the cross connection might be happening. Interesting, I found electrical tape wrapped around the wire bunch but the adhesive on the tape was more of sticky ooze versus holding the tape on. Maybe that is where the cross connection could be happening. just gotta figure out wire colors tracing. Seems both have same yellow and then one uses a white wire and the other uses a black wire!

Googs1080 · Post by **Googs1080** » 10 Mar 2015, 21:11

If anyone else has gremlins in the rear like i did, just pop off the plastic hinge cover and pull down the cloth/rubber sleeve. Pull the wire bundle up and you will find the broken/frayed wires. All but one in mine was frayed or broken. Thank you all very much