Volvo 940 and 960 instrument clusters suffer from printed circuit foil and solder joint troubles. I've had trouble with the ABS and Coolant Loss warning lights not working. The problem has been a break in the printed circuit track feeding those two warning lights. If your ABS or Coolant Loss light don't come on with the engine off and key in the run position, your car has this problem. 940s didn't come with a Coolant Loss warning light, but many of us have added them using the 960 Coolant Reservoir. Sometimes the Parking Brake warning light doesn't work in addition. The picture below shows three warning lights on the back of the cluster. Light 8 is for Coolant Loss, light 9 is for ABS, and light 10 is for the Parking Brake. The problem is the printed circuit track feeding lights 8 and 9 from light 10 will have a defect and not supply electricity. Installing a jumper wire from the solder joint just above lamp 10 to the printed circuit board a lamp 8 fixes the problem. It beats buying another instrument cluster that may have the same problem.

Nice solder joints, John. Did you find the actual cracks occurred where the flex circuit bends around the plastic frame?
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Art Benstein near Baltimore

"A study in the Washington Post says that women have better verbal skills than men. I just want to say to the authors of that study: "Duh." (Conan O'Brien)

I couldn't find the crack in the track, I just know it is there. For some reason, it is warning lamps 8 and 9 that give trouble, and sometimes warning lamp 10 (which would probably include lamps 11 and 18, see below). The Emergency Brake warning light was occasional along with warning lamps 8 and 9, when I bought the car. The speedometer was bad and I bought a used instrument cluster with a good speedometer. The used instrument cluster had no power to lamps 8 and 9, and the spare cluster I just bought had the same problem. Any one with a 900 series should check to see that all of the warning lamps, shown in the owner's manual, are functional.

The same track feeds warning lamp 11, BRAKE, and lamp 18, SERVICE. So those lamps may also fail depending on where the break is. I can install jumpers to all of them to save a car.
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john

I suspect that many of these fine cars will be scrapped due to owner frustration about instrument panel problems, including speedometer and PCB failures. Note that to do any of these repairs successfully, you really need a good wiring diagram of the panel. The only ones I am aware of are in the Volvo OEM Wiring Diagram books.
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See the 700/900 FAQ at the drop-down menu above right.

It is pretty easy to trace out the power tracks on the printed circuit without the wiring diagrams which I misplaced during the remodel.

The only thing on 940s which is inferior to 740 models, is the instrument cluster and speedometer. From my experience 50% of the 940/960 instrument clusters have printed circuit foils with bad circuit tracks.

Between the bad speedometer, failed warning lamps, and bad heater core I paid $1000 for a very nice car the owner didn't want to spend money on for those potentially expensive repairs.
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john

what specific soldering methods can you offer to minimize foil damage?

iron type, wattage, solder type.......anything really

I carefully scrape the plastic off of the foil to make it bright. I use a 25 watt iron with a chisel tip to quickly tin the foil. You must move fast and very quickly melt the solder onto the foil, or you'll curl the plastic base. I use electronic solder with resin flux which contains lead. The solder with lead in it works the best for me. I understand it is hard to get.
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john

Dear John,

May this find You well. I hope your New Year has started well and improves rapidly. Your research should go into the FAQs!!

Lead/Tin solders can be had from Qualitek (in Illinois, 630-628-8083). While I doubt they sell small amounts, they likely can direct you to wholesaler, who can recommend a retailer.

I have a roll of their Rosin Core solder (NC601). It is 0.02"/0.51mm in diameter. It is 63% Tin (Sn) and 37% Lead (Pb). It is ideal for fine electronic repair work: it melts at 364°F.

Hope this helps.

Yours faithfully,

Spook