Electrics guru's step inside

I'm trying to troubleshoot my non functional panel lights (heater and various switches backlights). Can anyone tell me where they get their 12V from and where they are grounded? I thought it was the Auxiliary lights relay, which I checked today and found to be working, as when I removed it the red and green lights which illuminate on the foglight switches no longer came on. I'm also not sure if that relay even controls the lights that aren't working. EDIT: its a 1989 740.

The dash lights and all the others are controled by one of the connectors on the back of the clocks, I know this after several hours and a very bad back, from trying to sort them for MOT. Looking at the clocks from the drivers seat, it is the connector behind the temp gauge side. Put your hand up the back, and play about with the connector, and they should come back on.

I don't know which car you have but will take a shot. The 760 and early 960 work on the same principle. They have a number of 1.2 watt bulbs that are fitted into sections of perspex prism. Each one will light up a number of switch units. The switch unit function does not matter - it is the proximity of the switches that determines which is lit by which bulb. I do not think that these panel lights are through any relay. They will have a common feed from the panel light rheostat switch and that may be where your problem lies. The earthing is usually down to a common earth point behind the radio unit (centre console). The lights may in fact be working as they do have a habit of coming out of the prisms - no bulb in the prism makes it look like the bulbs have failed. Volvo is very good at providing these bulbs/holders with just enough cable and anyone rummaging about behind the dash etc could accidentally pull them loose.

Do you mean the lights on the instrument cluster like the speedo, and all the warning lights? All those are working. The ones which don't are the ones to illuminate the heater dials, and the little diagrams on all the switches. For example, the little picture of the rear window demister etc. Also the light which illuminates the fuses, and the rear footwell light. All the bulbs look fine. That ground sounds like its worth investigating, maybe its been pulled loose. My car also does not have a rheostat for controlling the brightness of the lighting. I've found a multimeter, just needs a battery because its been left on as usual lol. I'll have a poke around with it tomorrow morning.

OK sorry thought you had no instrument lights as well. Could just be bulbs have gone, I know I have had to replace several on both my 740 and 940.

I hope its not just all the bulbs, that'd be pretty embarrassing... They all look as bulbs should do

I would still try to have ago at playing with that plug on the back of the clocks, that was what was wrong with the 740.

Thanks, I'll give it a try tomorrow.

... so err... how much are new bulbs from volvo? :laughing-smiley-003 I'll be needing a full set... I checked them all by eye and they all looked fine, but stuck one on a battery tonight and it didn't light. Then got out the multimeter and found 12 - 6V at the wires depending on which stage the ignition was at.

So I went out today to try and find some new bulbs / LED's. Top tip: instrument cluster warning lights take the same bulbs and get very little use compared to the switch ones and there's easily enough there so you can save money buying new ones that way. I wanted to try and get some red LED's to make them match my radio so I bought some 12V super brights, but the car only puts out about 7V so they're a bit dim. I'm not sure if its worth converting the bulb holders or just coloring in the bulbs red...