Heated(?) seats - here's a puzzle!

[Joe Harding]

340, 1988 1.4. Comes equipped with all the necessities (wheel at each corner, brakes etc.) and the odd luxury like heated seats.

Now here's the mystery. Heated seats don't. Here's my check list to date:

Power arrives at both switches. 12volt or thereabouts. Does not drop off at switch on of seat.
Seat element shows continuity with about 3 ohm on each seat. This yields a power of approx 50 watts according to my calculations, which seems about right for a bum-warmer.
Earth connections fine, less than half an ohm from connector to chassis (about 0.2 ohm from memory).

Current draw via fuse is 4amps per seat. Fuse shows no sign of volts drop.

So why do I get no heat from either seat? Is it simply buried too deep in the fabric to feel? Any one else seen (or failed to feel) this illogical problem?

Answers please on a postcard to this thread.

Thanks

[Pyssysalo]

There is a thermostatic switch in series with the resistor/heating wire. That switch cuts the current at 50...60°F. You can feel the warmth only in a very cold (25°F) morning.

It's now about 15°F here in Tampere, Finland. Weatherman said it's going to be 0°F in Monday morning. And I don't have heated seats in my '85 340 . Let's see how does the engine start then. Last winter (minus 25°F) it was five gas pedal pumps, 100% choke, 3 sec. starting, and the engine started up and kept running. Then immediately 50% choke. Heater begins to blow warm during scraping the windows and grooming the snow off. Good spark plugs and SAE 0W-50 synthetic oil is the secret.

[macplaxton]

Originally Posted by Joe Harding

Is it simply buried too deep in the fabric to feel?

Shoudn't be, should be able to feel the element through the cover if you know what to feel for.

I haven't looked too much into them to be honest, I know my 1982 343 has a heated driver's seat, but doesn't have a switch, it's automatic and I only noticed it 3 months after buying the car, when I nipped round to a newsagents and for a split second I thought I had an accident in my trousers!

In this weather they should work and be noticeably warm.

[Paul240480]

+1 you should be able to feel them with ease.

My old 340GL had a duff one on the drivers side & a good one on the passenger side. Said passenger side was great & most passengers only needed a minute or two of it before switching off. Never did get around to investigating the drivers one though.

[granitegob]

I would say its possibly the temp rating has been reduced to minimum

[Joe Harding]

Still doesn't answer my question though. There is current draw and presumably power output at 50 watts. That means a thermostat is switching in. No refreshing sense of trouser accidents though.

[TonyS9]

If you are consuming power you are heating somewhere. It is possible it has wrinkled up towards the back of the seat.

I replaced mine with a brand new one a while back and both seat and back pads had disappeared from the useful area.

Mine shows a resistance of 1.6R=90watts.

You should notice it, it is nice! To fix it just undo the hook rings at the hingle point and roll the cover up a bit.

[Joe Harding]

At last, it makes sense. I'll have a look and see. After all, unless we discard Ohm's law, what else can it be?

You're a star, sir! Thanks

[Joe Harding]

Still no further forward. Managed to put my hand on a heating pad whilst 4 amps going through it. Not even discernably warm. Weird!

[Wilbo8711]

mine is exactly the same, i shall investigate also!