Hello all,
Have a 94 Volvo 940 turbo Gauge or warning lights stop working intermittently, alternator fails due to the alternator exciter not lighting up.
I have had this in the shop several times and we have narrowed it down to the small plug "I think 4 wire white plug" in the middle of the instrument cluster. It has a white cap that is pushed on to keep it from falling off?
Anyways there seems to be an issue with the actual pins on this connector just not being tight enough and somehow it must wiggle loose or something but it never comes off. vehicle will start fine many times in a row then randomly the idiot lights will not light up so I reach up under the dash and jiggle the connector/wires on the pictured connector plug and the lights start working for up to a day or 3 weirdest thing. I have already replaced the instrument cluster so I am pretty sure I can rule that out as being the issue and chances of 2 clusters having the same issue is very slim I would think (well it is a Volvo so maybe that statement incorrect, lol).
At any rate I need to find a used or new plug with the wires attached so we can try splicing in a new/used connector that hopefully will not have the same issue. I think this plug is the same on the 740 and 940 of similar years.
I don't want to spend a bunch of money on a plug I do not know is going to work any better. Donations welcome :) I am located in Washington State, USA
Thanks
Rob

Do the solder repair to your gauge cluster.
I feel this is a mandatory fix to any 940, and have done it to both of my 945s.
I resolder every single joint on the cluster.

A good soldering iron helps.

Do this fix, then go from there.

https://turbobricks.com/maint.php?content=art0031

Thanks MrNabisco, I had already done that before I installed. I also cleaned the Ground Spook suggested which Hopefully will help but now having issues with the damn heater control valve so waiting for parts to show up to repair that then drive the vehicle again. fingers are crossed.
If anyone has plugs that have been cut or wiring harness for instrument cluster let me know

I am still suspicious of the instrument cluster. How about reflowing the circuit panel soldered joints and re-install the original cluster.

Marty

Pretty sure it is not the the cluster cause we had the same issue with the original. Most likely the wiring at the plug but I will give that a try for fun

Hi Robsha,

If anyone has plugs that have been cut or wiring harness for instrument cluster let me know
--> Try finding it at a pick n pull yard. This a rare item as wiring only comes with the car. Else you could try to open/dismantle the 4-wire plug casing itself using jewellers screwdriver and tighten those electrical contacts directly. Another option is to slip something thin (eg. paper/thin cardboard) beneath that blue ribbon cable on the cluster to create tighter fit.

From Volvo wiring diagram, that 4-wire plug carries both power and ground for the instrument cluster and input from speed sensor at differential. Same power also used for alternator exciter light.

Amarin.

Dear robsha,

Hope you're well. On an instrument cluster for a '94 940, there's only one four-wire connector with a "white cap". That connector goes to the speedometer. The "white cap" is an anti-tamper device: once the cap is removed, it cannot be re-installed and no replacement can be had for it.

If the speedometer's connector were faulty, you'd see that: the speed and/or mileage indicators would stop working completely or would work intermittently. If the speedometer works reliably, do NOT cut-and-splice a new connector onto the wires that go to it. You're more likely to create a problem where none exists.

The problem is more likely to be a corroded ground for the instrument cluster. If I recall correctly, this ground is behind the door-side panel in the driver's footwell. Be advised that an invisibly-thin layer of corrosion can disrupt the flow of electricity. Thus, do NOT rely on visual inspection.

Rather, use an aerosol corrosion-remover, e.g., Deoxit, to clean both the ground plate (welded to the body) and the connectors attached to it. Remove each ground wire and clean the ground plate and each connector, by spraying Deoxit on it according to direction on the spray can. Then, re-install the ground wires.

Please post back with your findings.

Hope this helps.

Yours faithfully,

Spook

Hey Spook,
thanks for that information I will check for that ground. I already used an aerosol corrosion-remover on both Instrument clusters which did seem to fix some other issues on the old cluster but not this issue. I will let you know what I find out but I do find it strange that that particular plug only controls the speedo but I cant really dispute this but strange when I jiggle that plug and the wires attached the idiot lights come back on.
I will look for that ground and clean it up and let you know if that helped.
Someone that I know had previous issues with his 89 240 and said that Volvo used a lot of fusible links and wondered if that may also be connected to the Cluster possibly causing issues as well.

OK cleaned up the ground and that appears not to be the issue