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Electrical: Heated Seats

Old 02-12-2019, 10:35 PM
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Default Electrical: Heated Seats

2003 Buick Park Avenue, Base model 3.8L.
Heated seats don't work.
Hi All, I've been working on my seats for about a month or so. Took out the passenger seat, took it apart and put more foam in it, a couple new motors and checked the heated seat elements etc.
The seat elements checked good continuity. the thermistor checked around 990 ohms and the FSM says it should be in the range between 800 and 1100 so that should be good.
Started doing some troubleshooting on the wiring in the car.
I thought I had found an open ground circuit. It had something like 3000 ohms between the heated seat switch and the control module under the seat. I couldn't find anything other than a loose connection in the fuse block going to this ground, there are 3 or so splices and they looked good, and the ground points on the body are tight and clean. so I repaired the fuse block and put it back together.
Good Continuity on the circuit! I thought I had fixed it. But the heated seats still didn't work!
After further checking, I found that with the key off the ground circuit shows good continuity but with the key on it went to high resistance(3k), the manual calls for less than 60 ohms.
BTW, I previously checked voltages at the BCM and Control module and everything was as it should be except the 5v signal from the switch is 5v at the input but only 2v when the switch is pressed for either hi or low heat. I don't know is this is normal.
And of course there isn't any voltage going to the elements but the 12v feeds are hot to the control module.
Basically, does anybody know what would cause the ground circuit to change like this?
This is a head scratcher for me.
Thanks for any input!
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Old 02-13-2019, 09:25 AM
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Not sure which ground you are talking about....

On your heated seat switches, when you press once, does hi light up? press again, does lo light up? press again, go out?

When you press a seat switch, do you hear the seat module click?

It sounds like you have access to the trouble tree, "Heated Seat Inop"? You followed it step by step? If you make one incorrect measurement, that will lead you astray....
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Old 02-13-2019, 01:02 PM
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Best to load test these circuits as a simple resistance measurement can look ok when in fact it'* bad.
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Old 02-13-2019, 03:06 PM
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Thanks for the tips guys.
When I hit the heated seat switch the light for hi comes on and i hear a click in the heated seat module. if i hit the switch again the light for low comes on and if I hit it again it goes off.
I do have a field service manual and am using the 'heated seat inop' troubleshooting section.
The ground wire from the switch goes through a fuse block and to a ground point on the A pillar and the ground wire from the module goes to the A pillar ground point (G201 on schematic). Having trouble finding all the ground splices. I think there are 3 in the harness.
I was checking the ground from the switch to G201 and reading hi resistance. I also got hi resistance from the BCM inhibit signal at the module connector. Which is supposed the be low.
I have been checking under load.
What threw me off was that the resistance goes low with the key off. I guess i need to ignore that and go by the trouble tree.
heading back out there now, will let you know what I find.
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Old 02-13-2019, 03:16 PM
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never done uploaded before. hope this works.
Attached Files
File Type: pdf
Scan_0001.pdf (544.1 KB, 8 views)
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Old 02-13-2019, 04:03 PM
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If you think you have a ground problem, the easiest thing to do is, shave some insulation off the ground wire at the harnesses(switch, module)......then run a redundant ground to those wires.......
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Old 02-13-2019, 05:29 PM
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thanks Tech II, I tried that and no change.
I started the troubleshooting chart again and still came up with hi resistance grounds and followed the steps further.
I did notice something. with key on and I hit the heated seat switch, the hi indicator lights up, and I hear the module click, but then after maybe 5 seconds I hear it click again. and then it will click again so I shut it off. Is that normal?
going to keep checking. Kind of stuck at the moment.
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Old 02-13-2019, 05:33 PM
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BTW Carfixer007, the manual says when checking for resistance to remove power and load from the circuit. I've always done it with them hooked up too. I guess I just learned something.
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Old 02-13-2019, 07:14 PM
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One question, did both seats fail at the same time?
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Old 02-13-2019, 08:06 PM
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I bought the car about 3 yrs ago and neither heated seat worked.
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