No heat seat
 

Volvo V70 my06 2.4l 170hp. Nothin fancy pancy. Just bought the car and the dealer and he refuses to sort it out, which leaves me in dispair of trying to fix it myself.

So I have no heat seat i either seats, drivers nor passenger side. I have voltage 15 volt to the thingy under the seats and meassured the seat elements to about 1 ohm in resistance.

What could possibly be the fault since the elements and the voltage is there and correct. Could it be the CCM or some relay spooking arround?


Would be so happy to get them working to the winter.

(excuse my poor eng writing, not native)

You should be getting battery voltage going into the heater module and much less voltage coming out to the pad plugs...... around 5v delivered in pulses/waves so check the module out voltage.

Pad resistance needs to be less than 1ohm.

I believe it uses what is known as pulse width modulation (PWM) whereby the voltage is switched on and off rapidly to control the temperature. That means you can't just connect up a 12v to the element and expect it to work. Likewise, you may not be able to get an accurate reading with a digital multimeter as demonstrated by the 15v you are seeing.

Can't offer much assistance with regard to resolving the problem with the dealer other than it's a 10+ year old used car and it's not they type of mechanical fault that a dealer warranty would normally cover.

On one of the circuits I had 0.4 ohms and the other about 1.3 ohms and we gotta take off about 0.3-4 ohms for the multimeter cables. So the OHM should be fine I supose. Check the connectors that nothin seemed burnt there.

I have 15 volts in and should have about 5 volts out, ok... will check that and see if that is the case.

Lets say that I ahve everything on the right side in that perspective that the seat is all fine. What could be wrong apart from that?

I know that but in the car declaration it is stated that they are under normal funtion and not that they are faulty. But we'll see in the future what is resolved and not in that matter. WOuld be nice though if I got some heat :)

So PWM that aint easy to test I guess, but could it be a faulty CCM since the signal is sent from there?

The fault codes I have for this issue are: CCM-DD12 and CCM-DD30, no signal to either seat.

Could it be the relay-box under the seat that have broken on both sides.

Check your leads resistance again. I would expect 0.1 to a maximum of 0.2 even on cheap leads which would give a net reading over 1.0 ohm which may be too high.

Let us know when you get a module out voltage at the plugs.

I have now tried to meassure the cables and this is what I have found if you have a look att the picture.

The thermostat or thirmister i did not manage to get a reading of in either voltage nor ohm's.

I have checked the fuses on the dashboard side and they are fine. But I have no clue to if there are any fuses in the CEM that could be faulty if someone is pointing to towards the fuses.

So you have volts into the module but not out which could point towards a faulty module but on the thermostat pins, you should be getting a few thousand ohms at least so if that is open circuit, I would say that your problem lies there.
To be certain, unplug the seat base and resistance test the thermostat pins again.

For some more information I alsao tested the input side to the seat which can be viewed in the picture below.