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Old 10-11-2020, 08:34 PM   #1
Rusty_ratchet
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Default S90 Headlights Not Working

1997 Volvo S90

The headlights do not work. I checked the headlights, fuses, and relay. I measured the contact voltage at the relay and it is 12.4V. The relay coil voltage is approx 8.4 V. I am trying to test the switch on the dash, but there are a number of contacts and don't know which ones I should be focused on. I did a little probing with an ohm meter, and measure approx 25 Ohms between two of the contacts. This seems too high for a switch. I'd appreciate any input.

Connector to car wiring on the left, switch on the right.


Below is a photo of the connector to car wiring. I wasn't able to get a good photo of the switch pins, but the measured 25 Ohms at the switch at pins corresponding to the pin on the lower left and upper right.
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Old 10-11-2020, 08:44 PM   #2
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Which relay did you check?
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Old 10-11-2020, 10:07 PM   #3
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Which relay did you check?
It is on the drivers side in a fuse/relay "box". I can take a photo in the morning if that would help.
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Old 10-11-2020, 10:17 PM   #4
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The problem is more likely the relay in the trunk. Yes, trunk. Pull up the left side floor panel that covers the place where a 240 spare would go. Feel along the edge of the opening toward the inner floor area. There is a bulb monitor relay clipped to the edge of the sheet metal. That is usually the reason the 960/S/V90 models loose the headlights.
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Old 10-11-2020, 10:31 PM   #5
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It is on the drivers side in a fuse/relay "box". I can take a photo in the morning if that would help.
I had no idea that there were headlight relays in the trunk! Thanks, I'll take a look tomorrow once it is light out!
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Old 10-11-2020, 11:26 PM   #6
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I had no idea that there were headlight relays in the trunk! Thanks, I'll take a look tomorrow once it is light out!
It is the bulb out monitor relay. A really odd place to put it.
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Old 10-12-2020, 07:46 PM   #7
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Is this what I am looking for?



How do I test this to see if it is broken or not?
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Old 10-12-2020, 08:02 PM   #8
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Yes. That is the bulb out relay. I have no idea how you can test it.
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Old 10-12-2020, 09:48 PM   #9
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Use a test lamp and a wiring diagram.

I can think of many ways to do circuit verification. On the quick, with NO diagram you could start with checking for continuity between the lamps and the relay.

Quickly looking at that pic, I see 4 circuits that have a "L" and an "R". That probably means "Left" and "Right" I would start with those. You can confirm, power, ground and continuity between the relay and the component. Maybe even jump power to the "L" and the "R" circuits with a jumper and see what comes on.

Or use a wiring diagram.
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Old 10-13-2020, 01:11 AM   #10
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Quote:
Originally Posted by Rusty_ratchet View Post
1997 Volvo S90

The headlights do not work.
Quote:
Originally Posted by 2manyturbos View Post
The problem is more likely the relay in the trunk.That is usually the reason the 960/S/V90 models loose the headlights.
Quote:
Originally Posted by Rusty_ratchet View Post
Is this what I am looking for?

I don't see anything about headlights.
Just "3 x Stoplight / 4 x Taillight"
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Old 10-13-2020, 11:14 AM   #11
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Time for a wiring diagram and a test lamp.
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Old 10-13-2020, 04:51 PM   #12
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Quote:
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Time for a wiring diagram and a test lamp.
Thanks. I'll start looking for a wiring diagram :-)
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Old 10-13-2020, 07:48 PM   #13
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Don't use a meter and don't front probe terminals.
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Old 10-13-2020, 10:10 PM   #14
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Quote:
Originally Posted by MasterBlaster View Post
I don't see anything about headlights.
Just "3 x Stoplight / 4 x Taillight"
I checked on my parts car today to see exactly with that relay controls and it does just do the rear tail lights. There has to be a second one that monitors the headlights.
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Old 10-13-2020, 11:31 PM   #15
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Quote:
Originally Posted by 2manyturbos View Post
I checked on my parts car today to see exactly with that relay controls and it does just do the rear tail lights. There has to be a second one that monitors the headlights.
Thanks for taking a look! I took another look at the headlight switch. It turns out that part of the plastic has broken that keeps the tabs in place (the switch was secure at the top, but the two pieces separated at the bottom). I turned on the car and saw that the lights came on when I squeezed the bottom of the switch together where the pieces separated. I ordered a new switch, and am gluing the old one so the headlights will work until the new switch arrives. Thank you for your help!
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Old 10-14-2020, 01:44 AM   #16
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I’m glad you figured it out. I had the same thing happen to a 940SE. It uses a very similar switch.
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