Slow to heat up

[T6Paul]

I don't know if there are several heating elements in parallel - then one failed would slow down the heating? @Robert @Dilbert

[Guide] Heating Seat Failure And Repair

My drivers seat heating has stopped working. After quick check with resistance meter I have discovered very high resistance (few kΩ) in the drivers cushion element, backrest element was still okay (few Ω) Next thing was to carry out some research and establish faulty component part number. It...

www.t6forum.com

Anyways, measuring the current (or resistance) would give some ideas. Either a traditional multimeter, or by almighty VCDS/OBDeleven via OBD diagnostics port.

Thanks, All parts of the seat get hot, VCDS would be the easiest, I'll see what I can find out

 

[Fluff34567]

I don't know if there are several heating elements in parallel - then one failed would slow down the heating? @Robert @Dilbert

[Guide] Heating Seat Failure And Repair

My drivers seat heating has stopped working. After quick check with resistance meter I have discovered very high resistance (few kΩ) in the drivers cushion element, backrest element was still okay (few Ω) Next thing was to carry out some research and establish faulty component part number. It...

www.t6forum.com

Anyways, measuring the current (or resistance) would give some ideas. Either a traditional multimeter, or by almighty VCDS/OBDeleven via OBD diagnostics port.

My seats also take a long time.. what seat materia do you have?

I have OBDeleven will have a look for a test.

 

[T6Paul]

My seats also take a long time.. what seat materia do you have?

My seats are the Caravelle leather / alcantara ones

 

[Fluff34567]

Mine also.

@mmi what seats have you got?

 

[mmi]

My seats also take a long time.. what seat materia do you have?

I have OBDeleven will have a look for a test.

Mine also.

@mmi what seats have you got?

Mine are just fabric/textile Simora.

 

[Dilbert]

I don't know if there are several heating elements in parallel - then one failed would slow down the heating?

The seat base element and seat back elements are in series. Any problems affect the whole seat. The elements are made from fine multi-strand enameled copper wire.

One of our captains seats was much slower to warm from new than the other seat and it never got to the same temperature as the other. The element finally failed as detailed here: https://www.t6forum.com/threads/guide-heating-seat-failure-and-repair.17340/#post-263946 You can see the element construction in the images.

Since repair it works as well as the other seat. I suspect that some of the strands in the multi-strand enameled wire were fractured all along. The point where ours failed was at the bottom of the grove where one of the steel wire braces ran across the seat base. They are very tight and I wonder if this had strained the element.

 

[Robert]

To get it diagnosed properly I would suggest to disconnect the plugs under the seat.
Then measure resistance of the back and the base element separately. Each one should read few ohms.

Also there is only one thermistor in the base element. It could be sending false feedback but that is very unlikely malfunction.

 

[Dilbert]

Each element measures around 1 ohm each. You should measure around 2 ohms between pins 3 (brown) and 4 (brown/blue) on 8 pin black connector T8. (Assuming your wiring is the same).

The thermistor (which is embedded at the rear of the base cushion) measures around 8.5K ohms between pin 2 (black/white) and pin 3 (brown) on the same connector.

The problem when some of the strands fracture (as I suspected) is that a very low current from a multimeter does not show it up.

 

[Rg_]

Mines the same, takes a while to reach temperature. It's normal.

 

[andys]

My seats heat up very quickly, I’m turning them down from full within a minute, often before even leaving the car park and the setting is down to 1 a couple of minutes later.

 

[musttriharder]

Each element measures around 1 ohm each. You should measure around 2 ohms between pins 3 (brown) and 4 (brown/blue) on 8 pin black connector T8. (Assuming your wiring is the same).

The thermistor (which is embedded at the rear of the base cushion) measures around 8.5K ohms between pin 2 (black/white) and pin 3 (brown) on the same connector.

The problem when some of the strands fracture (as I suspected) is that a very low current from a multimeter does not show it up.

Thank you so much for this. I've just installed the Kufatec loom, but I ordered the wrong seat elements and I wasn't sure which wires I needed to join together - I guessed correctly as I have the same resistance measurements you quote.

My heated seats still don't work though. Do you know if pin 2 receives a variable voltage from the HVAC controller (or indeed how the pressing the button translates to seat temp?). I have 12.5 volts at Pin 4 and Pin 3 is earthed - I'm trying to figure out if the relay I bought is knackered or the HVAC panel

 

[Dilbert]

Do you know if pin 2 receives a variable voltage from the HVAC controller

Sorry, I have not measured the exact voltages (other than know it was ~12V) or looked at the waveform to see if its a variable voltage, current limiting or variable duty cycle (PWM) that controls the variable temperature settings. Someone else may have some more info on this.

However, are you sure the elements you have installed are the correct wattage/resistance?

 

[musttriharder]

Sorry, I have not measured the exact voltages (other than know it was ~12V) or looked at the waveform to see if its a variable voltage, current limiting or variable duty cycle (PWM) that controls the variable temperature settings. Someone else may have some more info on this.

However, are you sure the elements you have installed are the correct wattage/resistance?

the resistance values are the same as you've quoted. They are genuine VW - from a T4 I think. How might I verify the wattage?

 

[Robert]

U = 12V - when ignition on and engine off
Than measure your current with ordinary multimeter in series and apply to below formula
P = U x I

Alternatively measure heating element resistance
and use this formula
P = U² / R

Accuracy of your final result will be down to the accuracy of your measuring device

 

[Dilbert]

How might I verify the wattage?

Easiest way is ohms law.

Power = V x V (voltage squared) divided by resistance. The problem you have is measuring the resistance accurately. 2.00 ohms at 12.5V would give you 78.13W. 2.20 ohms at the same voltage is 71.02W. 1.80 ohms is 86.81W. So you need a good multimeter to give an exact figure. Also, the resistance will increase as the element increases in temperature.

If you can measure the current, power is Voltage x Current.

A better practical check would be to compare your good seat to your repaired seat. You can check voltage, resistance (as accurate as you can) and current (using a DC clamp meter over one of the wires would be easiest).

 

[musttriharder]

Easiest way is ohms law.

Power = V x V (voltage squared) divided by resistance. The problem you have is measuring the resistance accurately. 2.00 ohms at 12.5V would give you 78.13W. 2.20 ohms at the same voltage is 71.02W. 1.80 ohms is 86.81W. So you need a good multimeter to give an exact figure. Also, the resistance will increase as the element increases in temperature.

If you can measure the current, power is Voltage x Current.

A better practical check would be to compare your good seat to your repaired seat. You can check voltage, resistance (as accurate as you can) and current (using a DC clamp meter over one of the wires would be easiest).

Thanks - I haven't got a good seat - it's a retrofit using the Kufatec loom. I was all reasonably straightforward until I bought the wrong elements

 

[musttriharder]

Ok, so I'm beginning to lose the will to live with my seats!

I've measured the resistance of the 2 new (correct) elements at 1.8 ohms combined between pins 3 and 4 and 10.4K Ohms between pins 2 and 3.

Ignition on, engine off:
Pin 3 (earth) of the Kufatec harness at 0.6 ohms
Pin 4 (live) of Kufatec harness at 12v

Ignition on, engine on, measured between pins 2 and 3
Switch on 3 (max) 14.07v
Switch on 2 (med) 14.07v
Switch on 1 (min) 14.07v
Switch off 0.06v

Seats don't heat at all.

A better practical check would be to compare your good seat to your repaired seat. You can check voltage, resistance (as accurate as you can) and current (using a DC clamp meter over one of the wires would be easiest).

Which of the 3 wires should I be checking for current @Dilbert ? They are all wrapped together quite tightly. If I put a DC clamp round all 3, I get 0 amps
Is there any way I can check the relay? That's the correct part number (5K0959772) and new
Thanks for any advice

 

[Grim Reaper]

Clamp meter around either the 12v feed OR the earth return, not both.
To increase accuracy you can (if you have enough wire) loop the wire through the clamp meter ring a second, third or fourth time and then divide the reading you get by 2, 3 or 4.

 

[Robert]

Alternatively if you don't have clamp meter you could connect your meter leads in series and measure your current directly. I would expect your reading to be below 10 amps.

 

[musttriharder]

I’ve carefully unwrapped some of the binding on the loom and put the dc clamp meter round pins 3, 6 and 7 in turn (the 2 live and one earth), and the result is 0.5 amps in all cases. The earth connection for the loom seems good, so I’m at a loss now really