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90' 740 Heated seats trouble shooting

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DeathbyE30
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90' 740 Heated seats trouble shooting

Post by DeathbyE30 » Thu Apr 07, 2016 9:20 pm

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.

benpineapple
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Re: 90' 740 Heated seats trouble shooting

Post by benpineapple » Fri Apr 08, 2016 8:42 am

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?
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93Regina
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Re: 90' 740 Heated seats trouble shooting

Post by 93Regina » Fri Apr 08, 2016 12:09 pm

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.

Image

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93Regina
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Re: 90' 740 Heated seats trouble shooting

Post by 93Regina » Fri Apr 08, 2016 12:14 pm


DeathbyE30
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DeathbyE30

Re: 90' 740 Heated seats trouble shooting

Post by DeathbyE30 » Sat Apr 09, 2016 8:04 pm

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
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Re: 90' 740 Heated seats trouble shooting

Post by DeathbyE30 » Mon Apr 11, 2016 6:31 pm

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

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93Regina
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Re: 90' 740 Heated seats trouble shooting

Post by 93Regina » Mon Apr 11, 2016 8:24 pm

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???

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