Hi Boppers.. I'm brand new to this forum. I own a 04 1.4tdi 90PS SD. I bought it a couple of years back and noticed it never seemed to get up to temperature. I guessed the thermostat was stuck open but I had other priorities so lived with it until recently. A while back, the heater stopped working. The blower works fine, just only blows cold. I changed the thermostat last week and bled the cooling system, including the top bleed tucked away under the scuttle. The engine now quickly reaches operating temperature and sits at a steady 90 degrees. Unfortunately, the heater still isn't working. Additionally, when starting, I get a big red temp warning flash up after a few seconds and an alarm. This goes away after a minute or two and doesn't re-occur whilst the car is running. The engine isn't overheating, leading me to think this is a sender fault. Anyone else experienced this?
1.4 tdi 90PS Heater issue
- Thread starter Ghengis
- Start date
bretti_kivi
Member
Scan it and return with the fault list. Everything else is guessing.
My guess is on a faulty sender and probably a flap or two.
My guess is on a faulty sender and probably a flap or two.
Rusty911
A2OC Donor
The temperature senders on these are in two parts, one half supplies the gauge, the other the ECU. They are prone to failure and if it's the ecu side, you might think all is well as your gauge is reading correctly. If you have a generic scanner you may be able to live scan engine temp and see what what it says.
The dedicated software for these is VCDS. You can get a Lite version or full, or there is a register of members like me who have full VCDS and will scan the car for you. In this case, unlikely you'll need VCDS at this stage.
Whatever, senders are relatively cheap, have a history of failing and are fairly easy to change.
As it happens, I'm not sure this explains the loss of heater. Try cycling the heater temp control from min to max several times. They can stick.
Oh, and a 'warm' welcome by the way
The dedicated software for these is VCDS. You can get a Lite version or full, or there is a register of members like me who have full VCDS and will scan the car for you. In this case, unlikely you'll need VCDS at this stage.
Whatever, senders are relatively cheap, have a history of failing and are fairly easy to change.
As it happens, I'm not sure this explains the loss of heater. Try cycling the heater temp control from min to max several times. They can stick.
Oh, and a 'warm' welcome by the way
audifan
A2OC Donor
Welcome Ghengis, The ability to scan is extremely useful so suggest you go the VCDS route. In the mean time although we are not certain does the dash warning light look like this one?
This is the low coolant sensor. It can be triggered by obviously low coolant level either it is low or the car may be on a hill giving a false low level. The sensor itself can get covered in debris from the coolant especially if it has not been changed when required or worse if the wrong type of coolant has been used. This can be fixed by cleaning the reservoir were the sensor is fitted or by replacing the reservoir for new.
As for the lack of cabin heat, the heater flaps could be stuck as has already been suggested and would need exercising by selecting the temp from low to hi REPEATEDLY with the engine running for a considerable length of time, but if the motor has failed it will need to be replaced. The system could well be full of sludge and debris especially if someone has used the wrong coolant or mixed incompatible coolants and will need to be completely flushed to remove all traces. With the cars perhaps being stationery for long periods this sludge could have partially or completely blocked the heater matrix.
This is the low coolant sensor. It can be triggered by obviously low coolant level either it is low or the car may be on a hill giving a false low level. The sensor itself can get covered in debris from the coolant especially if it has not been changed when required or worse if the wrong type of coolant has been used. This can be fixed by cleaning the reservoir were the sensor is fitted or by replacing the reservoir for new.
As for the lack of cabin heat, the heater flaps could be stuck as has already been suggested and would need exercising by selecting the temp from low to hi REPEATEDLY with the engine running for a considerable length of time, but if the motor has failed it will need to be replaced. The system could well be full of sludge and debris especially if someone has used the wrong coolant or mixed incompatible coolants and will need to be completely flushed to remove all traces. With the cars perhaps being stationery for long periods this sludge could have partially or completely blocked the heater matrix.
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Hi Audifan, thanks for your response. The dash warning light does indeed look like that. It only tends to light up when starting from cold. The coolant is at the correct level in the expansion bottle. Obviously, I lost quite a bit when I changed the thermostat, but I topped it up with pink anti-freeze which was what was in there before. I bled it at the lower bleed first then the upper. The upper was seized and took a fair bit of effort to free it, so when I finally bled it it was up to temperature and warmed my hands up nicely, a bit too nicely tbh. I've instructed my daughter that it's now her job to scroll between lo and hi on the temperature buttons whenever we're travelling. we've only made one short journey like this so far, but I notice that the fan blows nicely on lo, but just one bar on hi. (Heater on Auto.) Will try and get fault codes scanned this week.
The temperature senders on these are in two parts, one half supplies the gauge, the other the ECU. They are prone to failure and if it's the ecu side, you might think all is well as your gauge is reading correctly. If you have a generic scanner you may be able to live scan engine temp and see what what it says.
The dedicated software for these is VCDS. You can get a Lite version or full, or there is a register of members like me who have full VCDS and will scan the car for you. In this case, unlikely you'll need VCDS at this stage.
Whatever, senders are relatively cheap, have a history of failing and are fairly easy to change.
As it happens, I'm not sure this explains the loss of heater. Try cycling the heater temp control from min to max several times. They can stick.
Oh, and a 'warm' welcome by the way
Thanks Rusty.. ?
Whereabouts is the sender located?
Rusty911
A2OC Donor
Assuming same as a 75, right hand side of cylinder head near the bulkhead when looking from front of car. IIRC it's pointing at the bulkhead as lies alongside the head: sorry no lic, but search A2OC temperature sender via google and you'll find pics on here. It's worth greasing the O-ring to help prevent it dropping down the back of the engine, plus it's easy to lose the retaining clip in same way. Worth spreading a rag underneath the area to catch errant escapees.
Good call on level sensor Mr @audifan , I had assumed you were getting an overheating warning.
bretti_kivi
Member
Failures are normally the potentiometer, nothing else. Flaps don't "stick".
The pot is the way that the car identifies where the flap is in relation to fully open or closed. If the track (or the wiper!) deteriorates through debris or corrosion of some kind, the car no longer knows what's up or down (or 1Mohm vs 10ohms) and therefore doesn't move anything. It could be either way; there might be a short, there might be infinite resistance. It doesn't know and can't tell and therefore doesn't try. "Manual" should work but might not, especially if the short is such that the system is convinced the flap is already in the correct position.
Exercising the flaps (or running a basic setting - open HVAC, something in field 001 and hit "Go" if I remember correctly) only ameliorates the problem in that it allows the car to re-learn what resistance is at 0% and 100% open and therefore understand when the flap is open or not. This might be enough to put off replacement, but it's not a cure. It can provide 1-2 years worth of relief.
And no, you can't get the pots separately, organizing that has been tried multiple times; they're a non-standard format.
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So this morning on the school run, I got my daughter to cycle between lo and hi on the heater control. The journey is not far enough to allow the engine to reach operating temp, but I continued for a few miles and kept up the exercise, not really expecting anything. Heater now works fine! I'm amazed. Thanks for all the advice. Now I just need to find what's causing the low coolant alarm to trigger.
bretti_kivi
Member
when you get a scan, I'd expect the temperature flap to appear on the list. The thing is that the system will also try to match the temperature on the output to your desired temperature.
So you can set it to two bars and 24C, and as the air warms, more will be pushed out, the fan will turn itself up. We use this a lot here when it's -10C; leave it on 24 and as the car finally gets warm just turn it back to 2 bars.
But if it's on "LO" and the car's cold, this is "correct" so fan may be deal with correctly. But the system can also decide to drop the fan level to suit the amount of warm available. Which would explain why the fan is on 1 bar at "HI"; output temperature does not fit with the desired, so the fan is calmed down.
To me it sounds like you have one, maybe two flaps with issues. I would also exercise up / down / vents / recirc and test which ones actually do what they should. Scanning can then confirm. A basic setting will cycle through everything.
So you can set it to two bars and 24C, and as the air warms, more will be pushed out, the fan will turn itself up. We use this a lot here when it's -10C; leave it on 24 and as the car finally gets warm just turn it back to 2 bars.
But if it's on "LO" and the car's cold, this is "correct" so fan may be deal with correctly. But the system can also decide to drop the fan level to suit the amount of warm available. Which would explain why the fan is on 1 bar at "HI"; output temperature does not fit with the desired, so the fan is calmed down.
To me it sounds like you have one, maybe two flaps with issues. I would also exercise up / down / vents / recirc and test which ones actually do what they should. Scanning can then confirm. A basic setting will cycle through everything.