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