850 heated seat not working

wildlifeguy · Post by **wildlifeguy** » 16 Nov 2009, 07:29

Good morning guys,
my wife's '96 850 has the heated seats, but no heat. the light comes on when we turn on the switch, however, the seat does not warm up. Is this a common fault (208, 000km's) in volvo's and what would be a quick diagnosis.
what an excellent forum this is.... makes for great late night reading and anytime quick tips for sure.

mike

mindshadow · Post by **mindshadow** » 16 Nov 2009, 08:25

I'd check the fuse first. I believe the lights for the buttons are on a separate fuse so just because the light comes on doesn't mean the fuse for the seats isn't blown.

Other than that you could get a multimeter out and try to find the source of things not working.

Maybe some of the more well-versed people on this forum will have a better idea of what to look for, but that's definitely where I would start.

rnicolas · Post by **rnicolas** » 16 Nov 2009, 08:38

I had the same problem,
I look under the seats an noticed the wire was broken towards the seat.

wildlifeguy · Post by **wildlifeguy** » 16 Nov 2009, 08:52

fuse works fine, same fuse as pwr mirrors (#26 in fuse box).
Will visual the wiring under the seat tonite.

thanks

FCPEURO · Post by **FCPEURO** » 16 Nov 2009, 10:26

I know the RWD Volvos had big issues with the heated seats going bad. If you sat in the seat the wrong way, it would stop working.

Also, if anyone has ever pressed there knee into the seat or had something heavy that had a small foot print, that could break the heater part inside the seat.

The best thing to do would be to use a multimeter on it and see what you find.

Post by **polskamafia mjl** » 16 Nov 2009, 14:16

I can't remember where but there is a really nice and long thread with a detailed discussion about diagnosing the seat warmers. Try searching for it and I'll look around as well, if I find it I'll post the link here.

Post by **matthew1** » 16 Nov 2009, 14:32

Often the wires pull out of the seat thermostat, or the thermostat's small connectors break.

Follow wires that run up directly under the seat.

Heated Seat Thermostat Fix Tutorial via Volvo Repair Database.

Post by **Ozark Lee** » 16 Nov 2009, 20:02

Here is my standard method of diagnosing seat heater problems:

Look under the seat, on the right hand side as you look at it from the footwell, and locate the power connector for the seat.

It is the large white connector with the Yellow/Red wire and the Black wires.

Use a voltmeter and, with the seat heater switch on and the key on, check for battery voltage between the Yellow/Red wires and the Black wires. If it measures good there it means that the switch is good and the wiring to the seat is good.

You next need to locate the heater pad plugs, they are just below the front edge of the seat, they are both 2 conductor connectors. One connector is gray and the other is black.

They are pictured here:

Backprobe the red wire on the black connector and check it for battery voltage as well, the black wires on the power connector are a good ground point for the meter.

If you have good voltage there it means that the thermostat and its circuit are good. If you don't have voltage there it means that the thermostat is bad (not likely) or the wiring to the thermostat has come unplugged (more likely). The thermostat is located near the rear of the bottom seat cushion and it has a Red wire and a Red/White wire going to it. Plugging it back in is tricky and is best accomplished from the back seat and having someone sitting in the seat - that someone will get goosed a bit.

Assuming that the voltage is good on the red wire next move to the yellow wire. On a normally working system you should read voltage there but it will be less than full battery voltage.

If you read full battery voltage on the Yellow wire then the seatback heater element has burned out.

If you read no voltage there then the seat bottom heater element has burned out.

...Lee

wildlifeguy · Post by **wildlifeguy** » 17 Nov 2009, 17:44

found the problem. Simple broken wire out of thermostat.
But thanks to all the posts, I'll be ready for the any other issues which may arise.
now onto the blown instrument bulb which display time and other info.

mike

Post by **vjaneczko** » 27 Nov 2009, 21:48

Several years ago, within one day of each other, the seats became painfully hot and then didn't heat at all.

Shortly after that, I received a recall notice for my '97 850 GLT regarding the thermostats for each seat. If memory serves, the notice indicated that the thermo could fail and cause the heating element to burn out and in some severe cases, cause the foam to catch on fire. When I took the car in, I asked the tech if the recall covered the elements and he said; "Nope. The problem was with the thermostat and that's all that the recall covers". Asking what it would cost to repair, he guessed around $300 a seat.

So I never verified that the elements were burnt-out, so I'll have to take a peek!