bulb failure sensor 1977 245

jh240 · Post by **jh240** » 19 Jul 2011, 10:05

So... I've been having troubles with the tail lights on my 1977 Volvo 245 and have undertaken fixing it myself... The wires have continuity all the way up to the connector in the dash, and 12v is sitting on the fuse... I was under the impression the bulb failure sensor relay was under the dash on the far driver's side but can't find it anywhere... does it plug into a wiring harness piece? a permanant socket in the dash? I just don't know where to look next but was told that when that relay goes bad (or isn't there) that you will experience weird issues with the lights... Can anybody out there giv e me a lead on where to look next?

Post by **billofdurham** » 19 Jul 2011, 11:22

The bulb failure unit is up under the dash on the driver's side as in the attached:-

240 1986 relays..pdf: (120.98 KiB) Downloaded 260 times

The unit is round and look like this:-

: Bulb failure unit.JPG (5.22 KiB) Viewed 2167 times

The unit works by comparing pairs of bulbs and if one of the pair fails it will set the bulb failure light. If the unit does go bad it can cause failure of one or more pairs of lights. If you don't have 12 volts to the rear light bulb holders check to see if you have 12 volts to the brake light bulb holders or any of the other lights working through the unit. If you do then this indicates a failure of the unit on the rear lights portion only. The only remedy is to replace the unit or take it out of the loop altogether and splice the appropriate wires.

Bill.

jh240 · Post by **jh240** » 19 Jul 2011, 12:35

thanks! I've got a replacement yellow one that is what this car should have... all I can find under there though is a round canister with 12pins on it as opposed to 15... Is this just a different stock part or has someone possibly messed with it and replaced the part wrong, while adding different connectors?

jh240 · Post by **jh240** » 19 Jul 2011, 12:36

I'm pretty sure it's just the instrument cluster hookup from looking at wiring diagrams.

Post by **billofdurham** » 20 Jul 2011, 12:33

My book shows the bulb failure sensor on the '77 245 has 12 pins and is red.

Bill.

jh240 · Post by **jh240** » 20 Jul 2011, 15:42

got it and it solved all my issues... It was smaller than any of the replacements I've seen and was silver... I was unable to purchase a replacement of the right size so I busted it open and jumped the proper connections for the tail lights. I DO want to know the story of how it has a funky sensor though

Post by **billofdurham** » 21 Jul 2011, 11:54

Thank you for the update.

Bill.