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240 91, heated seat switch?

J

jambo

Member
Joined
May 15, 2005
Both front seats heated, but now the driver's side switch on-indicator doesn't light and the warm is gone on that side :-( The wiring diagram I'm guessin' for the '90 is going to be the same as for the '91 (?) http://justplainobvious.blogspot.com/2012/01/fix-heated-seats-in-volvo-240.html and the guy who publishes this says "If your heated-seat indicator bulb illuminates, it means the fuse and wiring up to that point is good." Does this mean conversely that if the left bulb doesn't illuminate but the right (passenger) side does then the problem is likely with the driver's-side switch itself?
 
Light bulbs in the switches could be out, or switches could be bad. Check with a DVOM. Should see 12V on one side of the switch with the key on. Should see continuity through the switch with the switch closed.
 
It might be my foggy memory but I also seem to recall that the seat won’t come on at all unless the interior temp of the car is below a certain threshold. When it does come on it should be full power for the first few seconds and if it’s not extremely cold it will go to like 1/2 power.

Could be wrong but I recall reading that somewhere...
 
If the fuses are fine and you haven't taken the console apart, then it is probably easiest to check for 12V at the connector under the seat. If you have 12V there then the problem is in the seat. If not, it is likely the switch.
 
The contacts inside the switches get dirty. You can clean the switches by carefully taking them apart. My a/c switch did this and cleaning it fixed it. You use a couple small screwdrivers to pry the plastic housing tabs apart to get to the parts inside. Heated seat switches are in a location that gets a lot of dirt.
 
The thermostats in the seat grids have a tendency to fail. I bypassed them on mine and it works fine now. If you're getting 12 volts at the connector under the seat that would be the next thing to check.
 
mattd1205 said:
The thermostats in the seat grids have a tendency to fail. I bypassed them on mine and it works fine now. If you're getting 12 volts at the connector under the seat that would be the next thing to check.
Click to expand...

If you bypass the thermostats won't the seat grids overheat? Fire much?
 
nel621 said:
If you bypass the thermostats won't the seat grids overheat? Fire much?
Click to expand...

I did this and regulated the temp using the switch on the dash. It was inconvenient so I built a thermostat that goes under the seat and has a thermistor (as temp sensor) under the heating element. It works but it would have been a lot easier to just buy a new seat heater.
 
You used to be able to buy that exact thermostat from electronics suppliers like digikey and newark. But I haven't check them for that part for a long time. Volvo does still supply it, too. 3521725 is available from gcp.se for $23 plus shipping.
 
On this 240 both sides feed from fuse 13, 16 amps. The indicator bulb on the passenger-side was coming on when the switch was pushed, and the driver's-side quit coming on a couple of weeks ago. Both switches looked exceptionally clean so I didn't bother taking them apart. Assuming the passenger-side switch was good (bulb lit), I put it on the driver's side. Still no rumpus warmth. Slid the seat forward and cut into the red and the black insulation on the wires underneath, to read 12 dc volts.

I am done until warmer weather, when I'll start to wonder how easy it is to take out the seats. "It's just four bolts" is encouraging, but somehow working in a cold garage-- which I have to drive to, forty miles away, otherwise having just a parking space outside my apartment-- for any number of hours to make the seat-warmer heat for a couple of months, until spring, doesn't cut the mustard. Guess it's not that important to me, but I'm glad to have done some trouble-shooting.

I'll still put a voltmeter on the switches to be sure. But looks like something in the seat grid: thermostat, best bet.

Thanks, everyone.
 
The wires under the seat should go to a connector. You should be able to measure at the connector and not have to cut back insulation.

Once my seats are out of the car I work on them in my living room. It's not a bad job :-)
 
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