This one has me stumped. I have a 93 940 wagon with heated leather seats.
Both seat heaters were inop , but after cleaning both switches the drivers side came alive.
The passengers side is still inop.
After checking out FAQ re the seat heaters it looks as though Volvo used a relay/thermostat clamped under the seat carriage. sure enough that little
green unit was under the drivers seat but missing under the passengers seat. Wires with connectors just hanging under there with no relay in sight.
Checked a few sites for the relay but unable to locate anything close. Even Dave Barton's site, noted for having this type of oddball stuff, had nothing.
Anybody have any experience with this type of problem?? Any ideas??

Dear Dom's940,

Hope you're well. If you can speak/read Ukrainian, see: http://vegaauto.com.ua/search/3523890/VOLVO.html . This is the seat heater relay for leather seats.

There's also a relay specifically for cloth-upholstered seats. Sprechen Sie Deutsch? If your German is good, see: https://www.teilehaber.de/itm/volvo-s90-v90-940-960-740-sitzheizung-steuergeraet-rep-3523889-volvo-3523889-src5518923.html .

I believe these parts - Volvo #3523889 and 3523890 - are what you need. I think they're no-longer-available (NLA) in the US. Suppliers in Germany and Ukraine may have: (a) old-stock Volvo brand items or (b) an aftermarket equivalent.

Before ordering, verify that the passenger seat actually has the heating element. There's no point spending $100+ for a part, that is useless if there's no heating element installed.

I may have one of these. I'd not use seat heaters: a seat heater malfunction could cause serious brain damage!!

Hope this helps.

Yours faithfully,

Spook