power seat

mikeyd · Post by **mikeyd** » 17 Apr 2018, 08:19

im a little stumped i have a 2004 s40 2.4L in regards to the D/S power seat I checked fuses all good i have what seems to be a good switch only because when i take the plug off the top of one of the motors and put a tester to it i get 12v so the motors are getting power the strange part is if i jump the motor any of them directly to the battery they will operate ??? what am i missing is there a relay somewhere any help would be appreciated

Post by **regent** » 17 Apr 2018, 08:52

Maybe the schematics will help you:

http://www.volvowiringdiagrams.com/?dir ... 20Diagrams

Look for 3/27, this is your Pass. Side seat control, check if the ground to the seat control is solid (with a test light bulb rather than a meter).

mikeyd · Post by **mikeyd** » 17 Apr 2018, 15:10

thanks for the schematics but does it matter that the pass seat is manual

Post by **regent** » 18 Apr 2018, 08:02

Sorry, I misread; you are indeed looking at 3/26 for D/S.

P/S and D/S have identical arrangement; same troubleshooting approach to either.

The seat control w/memory is data-networked and also receives 12V power from two fuses (F85 is always hot, and F86 is powered by the interior lighting relay 2/89 that is switched On/Off by the CEM).

This would be your case if your pass. side is manual. If power(s) and ground check good, I would suspect the module itself (you've already confirmed good working motors in there)

mikeyd · Post by **mikeyd** » 19 Apr 2018, 11:38

regent here s the newest thing if i back feed a wire from battery ground into either of the 2 motor wires the switch will operate until i go to operate the back fed motor then the fuse will blow do you think its ground related im getting close lol

Post by **mrbrian200** » 19 Apr 2018, 11:52

mikeyd wrote: ↑19 Apr 2018, 11:38 regent here s the newest thing if i back feed a wire from battery ground into either of the 2 motor wires the switch will operate until i go to operate the back fed motor then the fuse will blow do you think its ground related im getting close lol

You've probably got a broken trace/bad solder joint on the control circuit board, or a broken wire (ground path for the motors) in the harness somewhere. Since rerouting the motor grounds restores functionality, the logic/CAN functionality appears to be fine. Trace the ground path with an ohmmeter. or test light (a test light should illuminate when you're bridging across the break while attempting adjust the seat via the controls).

mikeyd · Post by **mikeyd** » 20 Apr 2018, 07:31

mrbrain i tested continuity from as far as the b pillar it goes into the frame from there but idid have continuity from that ground point to the plug for the seat switch i also tested from the main plug under the seat to the seat plug and it looks good when you say trace the ground path what path is that basically is there an easier fix or is this going to be a tracing nightmare

there are similar looking plugs under the pass seat could it be a ground issue somewhere there????thanks for your time

Post by **regent** » 20 Apr 2018, 08:22

mikeyd wrote: ↑19 Apr 2018, 11:38 regent here s the newest thing if i back feed a wire from battery ground into either of the 2 motor wires the switch will operate until i go to operate the back fed motor then the fuse will blow do you think its ground related im getting close lol

Please do not do that smoke test again...

When you ground one wire of the motor solid to Batt Negative and then apply reverse polarity via control button, the fuse will definitely blow because of short circuit current - that is what it is designed to do.

mrbrian200 pointed out your problem exactly: you need to look for a

broken trace/bad solder joint on the control circuit board, or a broken wire (ground path for the motors) in the harness somewhere