PaulW

JimR thinks that I have some special skill. Jim, you can do this too! The wiring diagrams in the Bently are actually very, very good.

So now onto how to troubleshoot. The diagram below shows the driver's side seat heater. You also really need the next page to see where some of the traces go, but I will just explain this one.

First, there are four buses at the top, they are the 30, 15, X and 31. They are all 12 VDC buses, and one is unswitched, one is switched, one is load reduction, and I can't remember what the last one is. But just know that it is either switched or unswitched power.

Then Ground is the line at the bottom. Anything that goes from the top to the bottom is a load and wiring. So you trace from the top to the bottom.

<img src="http://www.audipages.com/Tech_Articles/electrical_equipment/seatheater1.JPG">

The switch has unswitched power that provides power to the heating element, the control switch is powered from the X bus, which is the load reduction relay I believe. It's switched with the ignition, but not on when the starter switch is turned to "start".

So you could basically check almost everything from either the switch or the green connector under the seat.

You could pull the switch (see audipages iPod installation procedure on how to get to the switch, use two small allen wrenchs attached to vice grips to remove the center vent).

Pull the connector off the switch. Using a multimeter set to DC range, measure the voltage at Terminal 1 to ground. Attach a wire to the engine block....it's a good ground and run it around to inside, then put the red lead of the multimeter in on pin 1 and the black lead to the ground wire, it should read 12 VDC. If so, it's good, if not, check ST5, S10, it's most likely blown.

Then check control power. Measure pin 5 voltage to ground with the ignition off. Should be 0. Turn the ignition on, should be 12 VDC. If not, check Fuse ST5, S2 (which is shown on the next page, look at it and follow the trace found on number 14 at the bottom, you'll see it goes to the X bus through the fuse).

Turn ignition off.

Switch the multimeter to resistance. Measure resistance of seat heater elements. Put one lead of the multimeter on pin 2 to ground. If there is an open circuit here, then no current will flow (an open circuit will be shown). If there is resistance, make a note of what it is, probably somewhere 1-3 ohms.

If it has a good reading, then pull the other seat heater switch (which you know works) and measure it's resistance. It should be the same. If it is roughly half of what you got, then one leg is open circuited.

These resistance readings could also be taken at T6K, which is the Green six pin connector under the seat. This is shown on the diagram above.

If you have both control power, seat heater element power, and contuniuty, then it's most likely the switch or the thermostat in the seat. They control the "electronic on off switch in the actual switch itself".

If you need more help after you get this far, post it and we'll go to a little further.

I'll have to throw this up on audipages.

pw

Feuerstein

Cooked nuts make for defective babies (at least that is what the story is in Europe).

With cloth seats, you don't need seat heating anyway, they don't get nearly as cold as the "dead cow" seats.

PlainRuss

&lt;The wiring diagrams in the Bently are actually very, very good.&gt;

They are exact copies (or at least the ones I have seen you post) of the factory diagrams.

TerminA8r

Everthing checked out like you said.
# 2 pin to ground and we got 2.6 ohms on driver side, then checked # 2 pin on passenger side and we got 4.5 ohms.
If I understand you right this means there is an open circut on the driver side.

What is the next step?

Does this mean that on of my elements are bad?

Thanks

PaulW

Since you have lower resistance on the driver's side, both elements are good. It has two paths for current to flow in parallel, therefore the lower resistance.

The passenger side, because it has the higher resistance, means only one of the two circuits has continuity.

Unless you have mis typed what you were writing and the driver's side is bad.

If so, then the next step would to be to perform surgery to change out the element....most likely an open circuit in there somewhere.

Or at least check the resistance one more time at the seat connector and make sure it's the same.

If one of the elements is open, all you can do is change it out. There are procedures how to get into the seat on the Bently and some of how to get into the back of the seat here.

pw

TerminA8r

Re: That's odd because Passenger seat works just fine.

TerminA8r

Re: I went back and rechecked and the reading is about the same on both sides.

PaulW

If you do, then you could have a bad thermostat....or bad ground....but does it have power?

TerminA8r

So far I have done this:

1. I have put the red lead of the multimeter in on pin 1 and the black lead to the ground wire, it reads 12.6 VDC. meaning it's good.

2.I Measured pin 5 voltage to ground with the ignition off. It reads 0. Turn the ignition on, it showed 12 VDC. meaning it's working good.

3.Turn ignition off.

Switch the multimeter to resistance. And put red lead of the multimeter on pin 2 to ground.
There is resistance, about 2.7 ohms.
Then I pulled the Passenger seat heater switch and measured it, and it was about the same, 2.8 ohms. meanig that both elements in both seats are good.

I think this means I have a bad thermostat.

What do I do next?