Where is the ground connection for driver's side headlight and parking light?
They are very dim on my car. Passenger side is fine.

If your grounds are OK run a wire directly from the battery to the live terminals on your headlights. See if that helps.

I had an '88 745 GLE that had a bad wire going to the headlight - no light, but I measured 12 volts in the socket.

I stripped the wire back, and about a foot from the headlight I found a bunch of black gunk and one copper strand that made a very bad connection!

The headlamp assembly chassis grounds are to ground rails at the front corner of the fenders behind the air box or washer bottle areas. They can be mildly awkward to get at.

If both high and low beam are noticeably dim on the one side compared to the other then suspect the grounds. Another possibility would be that the reflective coating in the headlamp is noticeably hazed compared to the other side.

Much more likely is a problem at the headlamp connector. It's not an uncommon problem and often becomes chronic once it starts. If there is poor contact in the connector or if you've changed to high intensity, high wattage bulbs then the connector can overheat, fatiguing the little female copper contact fingers which only makes the problem all the worse, even more heat and allowing corrosion to build up. I've seen quite badly deformed connectors from the heat. You can try to pinch the contact fingers together and use contact cleaner -that often provides at least temporary relief. Many people have to resort to cutting off the connector and splicing in a new one. Just be sure to weather seal the soldered splices, like using heat shrink tubing, preferably the self-sealing type. I've got one 940 that's had chronic dim headlamps since the day I got it and occasionally needs the connector tweaked and cleaned, like once or twice a year -I really should replace that connector one of these days.

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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Hi Boris,

When you say passenger side, you mean as you sit in 940, and you are in a left-hand drive region like US and Canada and France. So, the passenger side is the 940 right side.

See here for Mitchell Service wiring diagrams:
http://www.v8volvo.se/mekartips/volvo/index.html

In the 940 link page, you want to download the Volvo 940 1992 Michell.pdf file. Or merely open in the browser you use.

The low beam or high beam or both are dim?

At the headlight and parking light connector, find the black wire for each. The wire with black insulation connects to the nearby sheet metal under a self tapping metal screw with washer. These black ground wire terminate in ring terminals so far as I recall on 940.

You can loose the screw and wiggle the wire. Inspect for rust. Treat with some grease. Reinsert the screw in such a way as not to cut new thread. Place the screw tip in the sheet metal hole, and slowly turn the screw counter-clockwise until the screw sets or drops a bit indicating screw thread alignment with the thread in the sheet metal hole. The screw should take up the thread and tighten to beyond snug. Maybe 3-5 ft-lbs or tight enough not to loosen with regular car vibration. Use of grease lessens the counterforce friction presents.

The wire harness connector at the back of the 9004 headlight bulb can form corrosion. A wiggle may restore brightness. The same corner lamp brightness. I'll guess the turn signal bulb is not as bright or flashes at a different rate than the other unaffected side?

The black ground wires that terminate in ring terminals are collected under the single sheet metal screw. So maybe some corrosion there.

Yet look through the Volvo 940 1992 Michell.pdf. See PDF page 21 for wire colors. Though I doubt there may be a voltage drop causing a dim headlight and corner parking light. Yet may help to check voltage at the connector if a loosen and tighten at the black wire sheet metal screw connection to disrupt corrosion does not restore proper headlight and parking light brightness.

Sometimes corrosion can travel up into the ring term (or other crimped connector) barrel where the copper stranded wire is crimped.

Please read the Volvo 700-900 Series FAQ on the electrics of headlight and horns (copy and paste URL in a new browser tab or window):

https://www.brickboard.com/FAQ/700-900/ElectricalLightingHorns.htm

Questions?

Unemployed Technical Writer Boyeeeeee
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Jonathan Harshman Winters III: The Mightiest, Greatest, & Most Powerful North American Comedian & Comedic Actor in Perpetuity

Thanks!
This is exactly what I was looking for.

Hi Boris,

Works better now I hope?

You read responses from Dave Stevens and james_a_sousa here?

Please lettuce know.
--
Jonathan Harshman Winters III: The Mightiest, Greatest, & Most Powerful North American Comedian & Comedic Actor in Perpetuity