OBP

Looking for some advice on a weird seat heater issue on my 05 TAP/Ecru. Drivers side seat heater tends to fail intermittently after I apply leather care liquid on the seat. Does not happen on the passenger side. In winter, it failed for nearly a week before coming back to life. Yesterday it failed for the evening, then started working again today. Each time right after I applied leather care to the seats. Same amount applied to passenger and driver's seat and the passenger seat is always OK.

Any idea what is causing this ?

Of course each time I go to the dealer, it is working fine !!!!

nwcn98

I'd take a close look at the switch 'wheel'

redliner8

iTrader: (1)

The leather cleaner wouldn't be the cause of the problem. Sounds like a lose connection somewhere. How do you know it's intermittent? The light on the heat switch turns off and on intermittently, or the seat heats intermittently?

OBP

The light on the little wheel switch is just fine. Lights up when I roll the wheel to the right. It's intermittent because I get better heat from the lower back heating pad than from the seat heating pad. The seat heating pad feels like it tries to heat up, then fails. All this while, the little wheel switch and its orange lamp work fine.

And all this only only happens when I apply leather cleaner on the seats. No problems otherwise.

VVTiBob

How, in the sense of pressure, are you applying the cleaner? In other words, are you putting your knee or some other sort of odd pressure on the physical seat. Check this thread https://www.clublexus.com/forums/sc-...ted-seats.html and this thread https://www.clublexus.com/forums/sc-...t-on-dash.html comment #6 for info.

OBP

Hi Bob, thanks for the links - found one of them myself earlier on. No I don't put any special pressure on the seats when I clean them. I just wipe the cleaner on and spread it around. There is less pressure when i do this than when I sit on the seat.

The heater has been weak today - it takes much longer on the drivers side to warm up. The passenger side is fine.

VVTiBob

Well then I'd do your best to make sure all connectors are properly seated, i.e. nothing loose from the switch in the center console all the way to under the seats. I'd also examine the switch itself for signs voltage problems, if you have volt/ohm meter you can test/measure the resistance as you manipulate the wheel on each side to see it there's a difference. Also take a look at the fuse to see if there's any indication of a problem there. Other that those items, it might just be the heating element has reached the end of its useful lifespan.

OBP

Thanks Bob. Have not done anything yet but the heater is toasty warm today. Hmmmm

VVTiBob

Intermittent problems are the worst....Next week when your area gets "the worst cold snap in 50 years" it won't work at all. LOL

OBP

OK seat heater issues are back ( not that we really need it cos it is warming up but still ...). Two days ago, the rotary switches on the center console totally failed - no lights and no heat. Was only 6 hours after the drivers seat heater was used and it was warm when used.

Went home, checked three heater fuses: driver's side footwell, passenger side footwell and under the hood on the passenger side. Removed inspected and replaced. All looked good - no problems with the fuses. Swapped out one of the 50 amp fuses ( for the seat heater ) under the hood for another 50 amp fuse for something else.

Started car, drivers side seat heater worked, passenger side did not - lights on rotary switches light up. OK - at least something works.

Replaced fuses in all their original spots ( re-swapped the 50 amp one under the hood ).

Same thing - drivers side heater works, passenger side does not.

Next morning - nothing works - no lights on the rotary switches - nothing.

Drive about 4 or 5 miles, checked both switches - both now work and both seat heaters work.

Finally, going home that evening, check both seat heaters - drivers side works and passenger side does not work. Lights on rotary switches light up.

So to all the electrical wiring gurus out there, does this sound like some kind of shorting issue ? Or what do people think this could be ?

My passenger seat is rarely used so I don't know if the heating element should be broken or not ? My guess not ...

DarthSid

OBP, please refer to the attached diagrams. These diagrams are from my 02 SC430 Electrical Wiring Diagram book. I'm providing a position of the parts in the seats harness connectors and positions. I'm also providing a layout of the seat heater controllers which are directly in the seat. I suspect you may have a loose connection as stated by other members or worst case, a defective seat heater controller. Or as stated by VVTiBob, consider also inspecting the control switch and connections.

Lastly, I'm also providing a full diagram of the seat heater.

There is a main 50 amp fuse upstream which you stated you already inspected. Also inspect the 20 amp fuse down stream and connections as well.

OBP

Thanks Darth Sid

OBP

My latest finding in this ongoing challenge: the headlamp/parking lamp switch can "fix" the situation when my seat heater switches die. Usually, my head lamps are in Auto mode. Today, my seat heater rotary switches failed again. But when I recycled my headlamp switches from Auto down through parking lights only and then "off", the seat heater switches revived and both seat heaters worked. So something in my headlamp circuit is giving my seat heaters a jolt which revives them when they "fall asleep".

Next test - leave headlamps in the fully off position ( not Auto) to see if seat heaters work the next day. Will report back.

JDaveSC430

OBP; I'm having the same seat heater failure and when I turned headlamps from auto to off, the seat heater worked as always. my problem started after my airbag recall fix done in June at the dealer; it's in their shop now and at first they thought it was the controller, but, after trying a new one, they said that wasn't the problem. I told them about my copying your actions with the auto setting head light switch, and, they said the only thing thing the heated seats share in common wiring wise is the auto tele/tilt steering column ground connection. Dealer said the seat uses the same ground as the power wheel telescope/tilt function. So, my question to them is could this ground connection have been disturbed during the recall repair somehow?

I use my seat heater often year round due to back problems and know it was working prior to the dash removal and reinstall; and have told them that. I've tried to use it several times during this past summer and no heat; but, they headlight switch was always set to auto until I tried it yesterday while taking it to the dealer to change the controller; when I got to the dealer seat was still nice and hot and service manager came over and felt it and knows it was working now.

They are checking with Lexus engineers for help; so I am wondering if you ever had resolution to your issue like this; or if anyone with more wiring knowledge than me has any thoughts or suggestions? The auto light function works as always, and, with its sensor located on the upper dash it seems logical a wire or ground wire from that sensor could have been dislodged during the recall.

Lexus seems stumped at this time; many thanks in advance!
Dave H

OBP

Hey Dave, glad to hear someone else is experiencing my problems and I am not completely crazy. Of late, my seat heaters are working fine. Once in a while my passenger side will fail but it usually comes back on its own. Drivers side has been good since my last post. My headlamps are usually in auto mode and I have not recycled the headlamps to off recently.

Useful info on the elec ground issue connected to the steering wheel telescope circuit. Will discuss that with my tech the next time I need service.