90' 740 Heated seats trouble shooting

DeathbyE30 · Post by **DeathbyE30** » 07 Apr 2016, 21:20

Recently Purchased my first volvo. Its a 1990 740 wagon, 5 Speed with leather seats.
I've been fixing all the little things getting the car ready for inspection.

Anyways I'm on my final job, Fix the inop heated seats. SO under some basic diagnosing. Ive got power to the heater switch, power via the white signal wire out. At the under seat relay, Ive got 12v at the white wire, the large gauge red/black strip wire, and ground (which I checked for continuity to a seat bolt)

The issue I believe is the relay will click and send power to the other solid red wire for about 30 seconds. then clicks off. I've tried a second relay and still the same issue. Its currently in the low 60s upper 50s if that ambient temps.

Post by **benpineapple** » 08 Apr 2016, 08:42

Perhaps the elements in the seat itself are on their way out, and conducting poorly? The fact that you're measuring power out is good, but a dip in power would likely cause the relay to switch off. Odd that it's staying on as long as it is before cutting out.

If the relay goes off, and you immediately switch it back on, will it stay on for another 30 seconds, or go off quickly/immediately?

93Regina · Post by **93Regina** » 08 Apr 2016, 12:09

DeathbyE30 wrote:The issue I believe is.

Monday, 30 January 2012: Fix Heated Seats in Volvo 240

Safety: Heated Car Seats Could Pose Burn Danger

Reality: 95 850 turbo Up in flames with pics

When I replaced the HVAC fan, I left unplugged the heated seats, for one good reason.

93Regina · Post by **93Regina** » 08 Apr 2016, 12:14

Extreme DIY car mod

DeathbyE30 · Post by **DeathbyE30** » 09 Apr 2016, 20:04

Well, I believe I've found my issue. The lower heating element had failed. My question is are people bothering with buying new ones from a dealer? the lowest price I could find was 80 for just the lower pad. Has anyone used an aftermarket with success?

DeathbyE30 · Post by **DeathbyE30** » 11 Apr 2016, 18:31

Well, apparently that wasn't my complete issue. I repaired the heater element, and checked resistance its 3ohms, and shows good continuity. If direct voltage and ground is applied the seat heats up as it should. But with the relay in place it still clicks on for a few seconds and switches off. Do these relays have an internal thermostat? or could I really have 3 bad relays. They all came with the car So I'm not completely doubting it

93Regina · Post by **93Regina** » 11 Apr 2016, 20:24

DeathbyE30 wrote:But with the relay in place it still clicks

See this cite above: Monday, 30 January 2012: Fix Heated Seats in Volvo 240

I assume he covered this topic...no..yes???