PTC heater....

Fishman

Fishman

A2OC Donor
Hi, I don’t think the PTC heater is working correctly on my 2004MY AMF engined 1.4TDi SE.
I find loads on info on the Webasto auxiliary heating system but not so much on the PTC.
Here are my questions...

Does it require the ambient temp to be 7 Celsius or less like the Webasto?

Are there any ways of performing a diagnostic check on it?
Are they generally reliable units?
Are they easy to change?

As far as the wiring goes I can see that it is fused directly off the battery on a 150A fuse to the heater and then to a earth stud on the bottom of the drivers A pillar. I’ve put a CT clamp around the brown wire near the earth stud. I did not get a current reading. Which either means it’s not working because it’s faulty or because the pre required conditions.

It is purely a cabin heater and unlike the Webasto does not pre-heat the cooling system.

Please help, I’m cold ?
 
Fishman said:
Hi, I don’t think the PTC heater is working correctly on my 2004MY AMF engined 1.4TDi SE.
I find loads on info on the Webasto auxiliary heating system but not so much on the PTC.
Here are my questions...

Does it require the ambient temp to be 7 Celsius or less like the Webasto?

Are there any ways of performing a diagnostic check on it?
Are they generally reliable units?
Are they easy to change?

As far as the wiring goes I can see that it is fused directly off the battery on a 150A fuse to the heater and then to a earth stud on the bottom of the drivers A pillar. I’ve put a CT clamp around the brown wire near the earth stud. I did not get a current reading. Which either means it’s not working because it’s faulty or because the pre required conditions.

It is purely a cabin heater and unlike the Webasto does not pre-heat the cooling system.

Please help, I’m cold ?
Click to expand...
There was a bit of information in a recent thread, it may help, depends if you have read it.

A2 spec manufacture codes | How to decode | useful links

I struggle to find a way to verify the correct equipment code for the Electric Additional Heater that was an option to 2004 and 2005 diesels. It is possible that it was an option for petrol car too, though never seen one my selves. When I call people wrt if the car they are selling, have the...
www.a2oc.net

What is PTC?

Andy
 
Positive Temper Coefficient... it’s an electric heating element for heating the cabin (or not) quickly on cold mornings. It’s fitted to TDi’s from 2003(ish) onwards, prior to this the TDi has the Webasto heating system, a diesel heater which could pre-heat the engine coolant and therefore the cabin.
 
Ive been doing some digging on the aux heaters in the tdi, and am planning to retrofit a Webasto and water pump to preheat the car on cold mornings. During my digging I read that the PTC heater only comes on when the outside temp is below 5C and only comes on when the altenator is generating enough juice such that the heater doesnt delplete the battery. This is around 1500rpm. From some light testing with my 2003 tdi I can tell that this info is pretty accurate, as the heat through the vents is very noticable when temp is <5C and rpm >1500. You could sit with a fast idle on the next frosty morning. It only takes 10/15 seconds for the heat to start coming though
 
Edit: This probably applies to 1.2TDI only, but i'll leave it here atm...
---------------------
They should be pretty reliable. Mine starts almost as soon as i disable econ mode on climate, when it's under 6-7 or so degrees. No need to rev etc. I'ts pretty noticeable since engine noise changes like it's working harder to idle and overall voltage drops 0,5-1V (always shown on ColorMFA).
1.2TDI 2001 with 140A generator and 900W PTC.

As far as i can understand it has 2 heating levels, one relay switches 1/3 of PTC, another 2/3 of it, combined would work at full power. That's for ECU to decide, how much power to sacrifice for heat, so revving could add heating power. Was pretty sure it operates on different levels of power and revving helps, but have not done that (revving) for a while. ELSA seems to agree by showing me 2 relays, PTC in 3 parts and ECU managing them. Add Econ button to the mix.

From net i see:
On battery:
S88​
150 A​
Strip fuse

Fuses:
14​
Low heat output relay
30A​

31​
Brake light switchHeater element (crankcase breather) (MPI engine, diesel engine)Air mass meterLow heat output relayHigh heat output relayCruise control system switchRadiator fan control unitAdditional air heater control unitExhaust gas recirculation valve
10A​

Relays:
4​
High heat output relay (J360)

8​
Low heat output relay (J359)


Don't "relay" purely on my info thought, might not be same for other models, but might be a starting point.
Are the relays there, fuses there, are they done fusing or still operational?
 
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1.2 very different when it comes to Aux Heater. 1.4 has no dual heat and are pretty much all 1500W hence the more current draw on the alternator and increased rpm to make them kick in. Cold climate cars also have some differences to non cold climate countries.
 
Might as well discard my previous post....

If i open 2004 AMF on ELSA, it seems to have Additional heater control unit. By drawing i'd think it lives within same thing as PTC itself. Because of that i'd guess it can fail. Or communication issue that prevents it working.
 
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The set up was far better for the cold climate regions. The restrictions to make it work for 1.4 diesels in the UK make it difficult to say the least. Between the temperature - not an issue, the rpm - much higher than quoted, the alternator load - difficult to achieve to start the unit and hard to maintain as any extra load exceeds the alternator load setting and that is with 140A alternators. Most try to use the aux heat at the same time as the heated window, that never works for me.
 
Does a ct clamp work on DC? Thought it had to be AC for a ct to work.... might be better off directly measuring the current.?
 
If it has dial that indicates that you are measuring DC Amperes then it should work.
If it only shows AC, then it probably will not work.
Many of them at my local electronics shop webpage have DC capabilities too.

But does the car have climate or rotary dials? If rotary, then there seems to be some microswitch on some cars that needs to work, for heater to come alive.
 
So, it's a bit chilly here and I've just been out in the other car and I noticed the outside temp was around 2 degrees.

I got home and proved that my heater does work!!!

The mistake was that it needs to be under 5degrees ambient temp. The coolant to be cold (I think less than 50degrees) AND the alternator needs to be kicking out a good amount of current.

My error was to not fast idle to boost the alternator charging.
A lot of posts never get closure, hopefully this helps others that have the same issues!
 
And as far as I can see that is the problem with the aux electric heater. Keeping the alternator supplying enough juice. As soon as more load or less rpm is applied the heater trips off. Most cold journeys are dark and often wet, that equals lights, wipers and heater all on, resulting in the heater (aux) switching off. In my experience I have not seen the heater coming back on if the load has decreased on the alternator, but that may just be me.
The best way is to let the car run for 5-10 minutes at a fast idle with NOTHING turned on except the heater. Much to the annoyance of neighbours and not the best for the car nor the planet. Only then with good heat switch things on and drive off. It is a shame that a fast idle was not programmed into the ECU when the electric aux heater was switched on.
Perhaps this winter I'll play around with it and see if there is a best temperature to select to keep the heater running for its duration or if there is something else that can be done with the alternator. Pity there is nothing that can be done in VCDS to just lock it on until the coolant temp is at the level where the aux heater is disabled. Maybe if we all log how we used our heaters along with other relevant information this could give us a best practice to using it. Is it the same method for the 900W as the 1500W version, we may finally get to know the answers.
 
Could a fast idle be mapped in when the auxiliary heater is in use? It's main function is to demist fogged/iced windows on the driveway so as Audifan mentions it's a bit useless.

I believe it's so somehow controlled within the glowplug and engine heating system (I could be wrong).
 
alternator is already 120A or 140A for the diesels IIRC. The original aux heater is a better way to do it, but it's more complex to build which is why I'm sure this was done.

- Bret
 
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