Faulty heated seat

[V8andTurbos]

Hi all. My 2019 a class drivers heated seat has an intermittent fault. The heated seats works as normal usually. But sometimes I’ll turn it on and within a few secs it will turn off. Only the drivers seat.. is this a fix I could do myself or will I need to book in to the dealer?

 

[MrGreedy]

Hi all. My 2019 a class drivers heated seat has an intermittent fault. The heated seats works as normal usually. But sometimes I’ll turn it on and within a few secs it will turn off. Only the drivers seat.. is this a fix I could do myself or will I need to book in to the dealer?

Unless it's a loose connector, probably either under the seat, or at the rear of the seat and usually accessible by partially de-upholstering, then the job is more involved, including the fault finding.

To check the loose connectors, just have a look under the seat with a torch and check/wiggle with ignition definitely off, to see if any are loose.

I'm not up on modern Mercs, but the leather upholstery at the rear sides of the seat back (accessed from the rear passenger foot well area) can usually be pulled apart slightly to gain access to the heated seat pad connector.

If it's not the connector (the easiest check) the most likely culprit is a broken heating element.

The system usually works by turning on, checking for seat heating, and if it doesn't detect heating within a couple of seconds (e.g. due to broken heating wire) then it turns off.

A proper STAR code scan will probably give you a very very good start in terms of fault finding .

If the seat pad is duff, then it's a seat out, fully de-upholster, and either replace the duff pad, or more likely, replace the whole leather seat cover with integrated heat pad, which is of course an expensive way of getting a new pad but might be the only option Merc parts department give.

The tools to do the pad replacement are basically a socket set and probably some hog ring pliers plus hog rings and wire cutters, but it's a long tough job for a novice like me.

I've done both front seats in an Insignia a couple of years ago. I could buy one seat heat pad base and one heat pad back, £70 each from the dealer plus £30 for hog ring kit and a can of spray contact adhesive.

And 3 day's work.

If you find it is the heated pad element, I could recommend getting the pad/new seat cover, and taking it to a vehicle upholstery specialist and getting them to do it no doubt in a couple of hours due to their experience.

 

[V8andTurbos]

Thanks for the response. I’ll have a look at the wiring and see if it’s loose. Going further than that I’ve booked it into merc next week. Hopefully they should rectify the issue as it’s still under warranty.. I don’t have access to a STAR unfortunately

 

[MrGreedy]

Ah, great . If under warranty that's ideal. They might have produced updated seat pads since original fit and the new ones could be less susceptible. This is a common redesign part on cars as the original heat pads prove to be less robust than originally hoped (and you can't beat the testing of millions of users actually taking the cars put day in day out).

 

[V8andTurbos]

The seat heatings working as normal today. Checked wiring. Nothing obv loose.. in the meantime, till the seats repaired - is it still safe to use the heated seat? Don’t want to damage further or worse, cause a fire etc..

 

[MrGreedy]

I would have thought it okay. If the wire is broken, as per my earlier post, the system will run a fault check in a couple of seconds after switch on and turn itself off again if not working correctly.

 

[DrNick]

I'd keep using it. You want to break it properly if you can, otherwise it will come back as "no fault found"