back again with the back up lights

azureblue · Post by **azureblue** » 26 Jan 2019, 16:33

And on it goes - I was sure it was the PNP switch. I got a parts yard one, (blue and black male 9 pin type) and tested it for continuity on pins 1 and 2. I also tested the original, in the car, and both showed continuity in reverse. So maybe it isn't the pnp switch. So back to the back of the car - recheck the bulbs and they are good. test fuse F4 (10A) and it is good. Turn ignition key to II and leave car in Reverse. check for power between F4 terminals - nothing. Check F4 terminals for power to ground (the big bolt that holds the relay and fuse box on)- still no power. Pull Relay RM14, and I can hear it click. Wiggle it and I can hear it click. Swap with another identical relay - still no lights. BTW, RM14 is all by itself on the top row of relay sockets, one in a group of four, to the left, and is the only one in the left hand group of four top row sockets that is wired. And I've never messed with the relays back there.

So can anyone tell me what I am missing here? I really need to get the backup lights working so I can pass inspection before the end of Jan.

Thanks in advance.......

IslandV70 · Post by **IslandV70** » 27 Jan 2019, 05:37

Can you get a voltmeter into the relay socket? I don't have the Volvo wiring diagram in front of me, but normally a relay like this works as so:
There are 4 pins and corresponding sockets for them to fit into. One should go to ground, one should always have 12 volts + when the car is on, one leads to the backup light bulbs, and one gets 12 volts to turn the lights on. If you can take measurements there it would be a good start.
Note a relay with bad internal contacts will still click but not provide power to the lights.
One test is to pull the relay out and put a jumper wire between the 12 volt socket and the backup lights and see if they go on. Someone on here may have the exact terminal numbers for this test.

azureblue · Post by **azureblue** » 27 Jan 2019, 07:20

Thanks. I do have a voltmeter. I think I can find the relay pin out - I remember seeing somewhere. I tried swapping with an identical relay but the lights still didn't come on. But I will try the jumper and take some voltage readings.

Post by **jimmy57** » 27 Jan 2019, 07:32

The relay I see in the wiring diagram for reverse lights on on the right side of REM in the middle of the inboard mini relay set. There are 7 relay locations, not all used, with the shunt locations above. It is the middle of the 7. The wiring diagram has the relay terminals labeled 1-5 with the feed for lights on 5 and the out is 3. If there are numbers you could see where relay inserts they have 3 as th power in (5 on relay) and 1 as out to lights (3 on relay). jumpering those two connectors where relay inserts should turn lights on.

azureblue · Post by **azureblue** » 27 Jan 2019, 07:39

Much thanks - I found the pin numbers on the bottom of the relay. I'll get to it shortly.. Much appreciated.

IslandV70 · Post by **IslandV70** » 27 Jan 2019, 08:26

Make sure there is 12 volts on the power in side too

azureblue · Post by **azureblue** » 27 Jan 2019, 14:44

and it was the relay. I got one from another car, and the lights came on. IDK why swapping with another relay didn't make the lights work, but a new replacement did. Much thanks.

Post by **E Showell** » 29 Jan 2019, 11:02

Please put a check mark on this so we are aware of the resolution. Thanks.