Heater not working

Hello .. thanks for the donation .. much appreciated This sounds from your description, like you have a fault on the Motorized In-car Aspirator ... my manual does not supply any test procedure for this unit !! you could try disconnecting the wires and see if you get the same symptoms ? hope this helps .. let me know ! Motorized In-car Aspirator An intake grille (mounted on the fascia, outboard of the steering column and below the EOD vent) houses the aspirator thermister. The remotely mounted motor / fan assembly draws cabin air through the grille and thus over the thermistor; a flexible hose connects both components. The electrical resistance of the thermistor changes in response to variations in air temperature, this change being converted into an electrical signal. The A/CCM uses this signal to adjust the temperature, airflow and air distribution from the air conditioning unit.

11 Motorized in-car aspirator malfunction Possible Source(s): Harness/connector fault Sensor open/short circuit Action(s) to take: Panel fault codes are not stored for motorized in-car aspirator motor failure.

Hi Dave, thanks for the response.
I could not work out what the normal levels of donations are!

I removed the Motorized in-car aspirator and tested it, the small fan runs and the termistor's resistance changes when you warm it.

When running the engine with the aspirator removed it seems to operate as normal but perhaps not as good at regulating the temp, as you would expect.

With the engine running (and warm) I tried cooling and heating the aspirator's termistor and the system reacted to that as expected. Also I did not see the failure having waiting 30 mins but perhaps it does not show with the car stationary or perhaps I did not quite leave it long enough.

So I'm thinking that's not the problem.

I re-ran the inbuilt diagnostics, at first you get code 0 (no error) and the fan them starts to speed up (sometimes to full speed during the diagnostic cycles) and after 20-30 seconds I get one error code, then after another 10 seconds another and then sometimes a third. These are all active as they have bleeps.

When I reapeat the diags I get the same sequence except the error codes have some differences;

Try 1
Code 0 then after 30 sec code 14, then code 43, then code 46. 14,43 & 46 then cycle.
Try 2
Code 0 then after 30 sec code 43, then code 45. 43 and 46 then cycle.
Try3
Code 0 then after 30 sec code 43, then code 45
Try 4
Code 0 then after 30 sec code 14, then code 44

I tried the actuactor test sequence (20-27) but that did not change anything.

After a few diag cycles the errors were;
43(Cool Air By-Pass Servo Motor, 11 times)
34(Defrost Vent Feedback Potentiometer, once)
14 (? twice)
44(Defrost Servo Motor, twice)
45(Defrost Vent Feedback Potentiometer, once)
46(Foot Servo Motor, once)

I keep thinking back to the sound when I get a failure, which is like the center servo motor running but the A/CCM not reading the flap potentiometer correctly and it keeps driving the servo and the gears just click over at their end stop. But if that was the case I assume that I would see a 'Center Vent Feedback Potentiometer' failure code. I am assuming that Jag designed the system so that the flaps would not hit the end stops and then keep clicking!

However your answer seemed to fit well.

If you were working in this car what would you try or do next?

Many thanks.

Hello .. there is no set donation .. you give what you think the service we provide is worth to you .. any donation is a bonus and gladly recieved .. thank you

I would now be looking at the cool air by pass motor as this seems to be the main fault code coming up ? i would also have the vehicle scanned by jaguars PDU to see if that actually gives me the exact fault ? let me know


14 Water temperature input malfunction
Possible Source(s):
Instrument cluster output
Action(s) to take:
Refer to PDU

34 Defrost vent potentiometer fault
Possible Source(s):
Harness/connector fault
In certain circumstances the servo motor may over-travel and cause further logged faults. This may be cured, following fault rectification, by cycling the ignition ON-OFF-ON 3 times

43 Cool air by-pass motor fault
Possible Source(s):
Harness/connector fault
Servo motor seized or sticking
Flap seized or sticking
Action(s) to take:
Refer to PDU

43 Cool Air by-pass motor fault
Possible Source(s):
Harness/connector fault
Servo motor seized or sticking
Flap seized or sticking
Action(s) to take:
Refer to PDU

44 Defrost vent motor fault
Possible Source(s):
Harness/connector fault
Servo motor seized or sticking
Flap seized or sticking
Action(s) to take:
Refer to PDU

45 Centre vent motor fault
Possible Source(s):
Harness/connector fault
Servo motor seized or sticking
Flap seized or sticking
Action(s) to take:
Refer to PDU

46 Foot vent motor fault
Possible Source(s):
Harness/connector fault
Servo motor seized or sticking
Flap seized or sticking
Action(s) to take:
Refer to PDU

Many Thanks

I'll book it in an see what the PDU says.

some systems on HVAC do not throw out a fault code on the self test .... so it could be on one of these systems/sensors and we could be looking in totally the wrong place ?... let me know how you do !!

Hi Dave

I had the car checked with a PDU and it threw up codes;

B1268
B1264
B1263
B1266
B1267

Which all seem to be flap feedback potentiometers.

The garage want to change the control unit and all the servo/flaps which I think will be expensive and not the right solution.

I have seen that when you get one error (from the panel diagnostics) then some time later you tend to get a lot more errors.

I suspect that either the cool air bypass flap servo or it's potentiometer or maybe the physical flap is catching somehwere.

Other than that I suppose it could a problem with a common power supply for all the potentiometers which is failing after a period of time or when warm etc.

Anyway thanks for your help.

I did get hold of a .pdf copy of "SERVICE TRAINING COURSE 703 JAGUAR CLIMATE CONTROL SYSTEMS" which helped explain the system, but not my particular fault.

Did you ever fix this problem ? i am have the same problem and can not fix it.

Running, Have you had your car scanned to see which fault codes you have? I'm afraid the above people never posted back what they found or how or if they repaired it. Also please give as much information as you can on the car and what your problems and symptoms are.

Good day. Okay the car is a 2000 Jaguar XJ8 base 4.0l with single climate control. The problem is the HVAC will blow cold after driving for about 30 minutes. When this happens, you can change anything on the controls and it will not make a different. If you pull over shut the car off wait 5 min start the car the heat will come back sometimes. Now this is the odd part it will only do this if the temp outside is below
0 deg C. any time it is above 0 all work great.
Also, there are no error codes in the HVAC
I have replaced the heat pump and heater control valve (engine compartment) with brand new units.
New thermostat flushed the system. Back flushed heater core. Pulled out the Aspirator checked it and it works fine. So, the only thing left to do is pull the hot-cold blend door vent servo motor but I can not find were it is one tag said it is on passenger side floor easy to remove but its not there. On another tag it said driver side behind dash cluster. But there is no way to take it out sheet metal for dash in the way.
If this is the right one not sure.

That sounds like the circulation water pump protection circuit has an issue. It is supposed to shut off the pump if the coolant temperature is read as below 16C I would get it to shut down, then go out and feel the hoses around the pump. See if the water is actually moving. Or you could try a jumper from battery positive to the yellow wire that feeds the pump voltage.
Do you have a scan tool that can read live data, you might look at what it shows for coolant temperature when this happens.

As for the cold air bypass, aka blend door, you need to remove the dash to get to it. Then it takes about 30 second to change! However I cannot think of a reason why it would be temperature responsive. It's nothing more than a motor and a position sensor. They normally just fail in one position or will set a code if the sensor doesn't detect motion when the control attempts to move it.

Okay, here is what I am going to do: I am going to hook up a small light 12 volt to the pump yellow and black wire and feed the wires and light out side the hood at the base of the windshield. The light should stay on as long as the pump has power. As my wife drives if the air gets cold the light should go out and then I would know that the wires or the relay are my problem. I need to do it this way because it never gets cold running the engine in the driveway and you can never know when its going to happen. I will all so try the scan tool I have one that stores all data for 4 hour and then I can look at it on the computer.
I will get back to you after I try this idea. thank you.

Sounds like a plan. Keep us in the loop about what you find and we at least have a place to start.

Good day, so i hooked up the light and by luck the wife went for a drive and you guessed it the temperature went cold but the light stayed on. so that tells me it's not the pump or the wiring to it. So I though i would play with the heater control value. started the car all heated up and I unplugged the value it did get colder but i think it went to its default temperature which is 77 degrees not as cold as when your driving but maybe you need the wind to cool it down more. But what i found interesting was if you plug the value back in with the car still running the temperature will stay cold until you shut the car off and let the HVAC reset. just like when your out driving. this is the closes i have come to reproducing this problem. So i am now going to pull off the value and have a look at it. Do you know does the value work on 12 volts?

Yes it works on 12 volts, can I ask if when the heater blows cold can you hold each heater hose coming out the firewall to see if the are hot? If so you have a blend door actuator that could be bad and loses its value which makes it move. Here is the location so you can check it out. Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.

Okay, the motor is working which is a good thing. With the extra info you gave it sounds like the system is shutting off the coolant flow, if it was a blend door I would expect it would go from heat to cold almost instantly as the door closed, not a slow progression to cold air.
As a test you could bypass the heater valve mounted in the rats nest of heater hoses in the engine compartment. Then see if the system stays hot. If it does then there is some issue with the controller itself telling the valve to stop sending hot water to the heater core.