aircon dead as a dodo
Discussion
Just when you might actually need the aircon, its dead.
Got a long motorway run on Tuesday and I've no nice cold stuff.
The engine still starts to labour when I turn it on and its got lots of gas.
Aircon man says there's no power to pump, but I wasn't happy to let him start playing under the bonnet until I'd checked the fuse.
To save me taking out every one in turn and checking, thus almost certainly causing a load more faults to appear
,anyone know what number it uses?
Got a long motorway run on Tuesday and I've no nice cold stuff.
The engine still starts to labour when I turn it on and its got lots of gas.
Aircon man says there's no power to pump, but I wasn't happy to let him start playing under the bonnet until I'd checked the fuse.
To save me taking out every one in turn and checking, thus almost certainly causing a load more faults to appear
,anyone know what number it uses?I dont understand how it starts to 'labour' the engine when turned on,if theres no power to the compressor?The fuse is a 25A one on the Griff,and is the same one as used for the heated seats,sorry i dont have the no. to hand,but there arent many 25A fuses in there.
I had a similar issue with my griff,when there was plenty of gas,but the compressor wouldn't run.On mine it was a burnt out track on the control unit.I found out this as there should have been 12v on two of the four pins in the connector at the low pressure switch on the receiver drier(front grill),so you might want to check that also.The output power line which was dead going to this switch was coloured white with a pink tracer on mine.
I had a similar issue with my griff,when there was plenty of gas,but the compressor wouldn't run.On mine it was a burnt out track on the control unit.I found out this as there should have been 12v on two of the four pins in the connector at the low pressure switch on the receiver drier(front grill),so you might want to check that also.The output power line which was dead going to this switch was coloured white with a pink tracer on mine.
I'm going to have to go through a similar diagnosis on my aircon - it doesn't work consistently.
However, I seem to recall reading (on here somewhere?) that the ECU automatically increases the idle revs slightly to compensate for the compressor load. In my case, I can hear the revs increase, but no click from the electromagnetic clutch and hence no cold air.
However, I seem to recall reading (on here somewhere?) that the ECU automatically increases the idle revs slightly to compensate for the compressor load. In my case, I can hear the revs increase, but no click from the electromagnetic clutch and hence no cold air.
cool, thanks for that. I've now checked the relays and they *appear* to be ok. I can hear two clicks when I request aircon but the compressor does not consistently come on. The revs increase to compensate each time (as previously discussed).
Am I right in assuming the that first click is me requesting aircon, and the second click is for the compressor?
FWIW all this started the last time I had a fiddle in the footwell. Looks like I'm getting the multimeter out....
Am I right in assuming the that first click is me requesting aircon, and the second click is for the compressor?
FWIW all this started the last time I had a fiddle in the footwell. Looks like I'm getting the multimeter out....
Edited by jonathant on Sunday 16th July 18:47
jonathant said:
cool, thanks for that. I've now checked the relays and they *appear* to be ok. I can hear two clicks when I request aircon but the compressor does not consistently come on. The revs increase to compensate each time (as previously discussed).
Looks like I'm getting the multimeter out....
If the compressor relay is clicking on,when you turn on the a/c,then i think i'm right in saying that you will either have a poor earth for the compressor,or a break in the circuit going from the relay to the compreesor.I'm pretty certain that after this particular relay,there is nothing else in the circuit before the compressor itself. Looks like I'm getting the multimeter out....
Edited by mongoose on Sunday 16th July 21:43
Not sure about TVR air con, but most systems have a pressure sensor which if the system is low on gas
it will not start the system running because the gas also contains the lubricant for the pump and seals.
These sensors are about as reliable as the speedo sensor on your diff.
To test if the sensor has failed, remove the plug at the sensor and short the pins while turning on the air con with
the engine running. You should see the compressor start running, ie the inner part of the front pulley should rotate.
If you get cold air, its time for a new sensor (about 30 quid)
The sensor is usually mounted near the aircon radiator and looks a bit like an oil pressure sensor.
Hope this helps,
Cheers,
Paul
it will not start the system running because the gas also contains the lubricant for the pump and seals.
These sensors are about as reliable as the speedo sensor on your diff.
To test if the sensor has failed, remove the plug at the sensor and short the pins while turning on the air con with
the engine running. You should see the compressor start running, ie the inner part of the front pulley should rotate.
If you get cold air, its time for a new sensor (about 30 quid)
The sensor is usually mounted near the aircon radiator and looks a bit like an oil pressure sensor.
Hope this helps,
Cheers,
Paul
The pressure switch on these cars is mounted on top of the receiver drier at the front,as mentioned earlier.If the switch had failed then the compressor relay in the yellow holder would not operate,as the switch needs to send power back to operate this.If the switch was working intermittently,then this could be your problem of course.I'm getting the impression from what you've said though(johnathont),that this relay is working normally but the compressor is still intermittent?
Edited by mongoose on Sunday 16th July 21:44
mongoose said:
I'm getting the impression from what you've said though(johnathont),that this relay is working normally but the compressor is still intermittent?
yes. I definately hear two clicks in quick succession and *sometimes* the compressor doesn't start. To confuse matters, I think I also have a leak in the system and there's little gas because I never get cold air. <sigh>
Trev's going back to sort out the aircon leak and hopefully it'll do the compressor-not-spinning-up thing too.
Just add a little confusion and try and clarify a few points.
Yes there is an input in the ECU that automatically lifts the enhine rpm when the aircon is requested.
There could be a number of issues as to why the aircon may not be working.
The pressure switch that is fitted to these vehicles I believe is a trinary switch. This operates in the following way,
1) If the pressure in the system is too low it turns off the compressor
2) If the pressure is too high it will turn off the compressor
3) The third setting should bring in the cooling fans to maintain an acceptable working pressure in the system depending upon the ambient temperature.
The compressor is a very basic clutch type which tunrs on and off to pump the refrigerant around the system.
Evaporator thermostat, The evaporator is the item that cools the air that is entering the cabin. Inserted into the fins of the evaporator is a thermostat. The thermostat measures the temperature of the evaporator to prevent it from turning into a block of ice. If this item is faulty, moved position or has been incorrectly set it can cause all sorts of issues.
Not sure where you are located, I am in the midlands if you want a bit of free help I may be able to assist.
Yes there is an input in the ECU that automatically lifts the enhine rpm when the aircon is requested.
There could be a number of issues as to why the aircon may not be working.
The pressure switch that is fitted to these vehicles I believe is a trinary switch. This operates in the following way,
1) If the pressure in the system is too low it turns off the compressor
2) If the pressure is too high it will turn off the compressor
3) The third setting should bring in the cooling fans to maintain an acceptable working pressure in the system depending upon the ambient temperature.
The compressor is a very basic clutch type which tunrs on and off to pump the refrigerant around the system.
Evaporator thermostat, The evaporator is the item that cools the air that is entering the cabin. Inserted into the fins of the evaporator is a thermostat. The thermostat measures the temperature of the evaporator to prevent it from turning into a block of ice. If this item is faulty, moved position or has been incorrectly set it can cause all sorts of issues.
Not sure where you are located, I am in the midlands if you want a bit of free help I may be able to assist.
Simon, that certainly helps me understand the system more.
Just one question: If I request aircon and the pressure is too low (or high), I understand that the compressor will not run BUT.... I presume the "compressor relay" should not click, nor should the ECU raise the revs slightly?
Just one question: If I request aircon and the pressure is too low (or high), I understand that the compressor will not run BUT.... I presume the "compressor relay" should not click, nor should the ECU raise the revs slightly?
Jonathon,
My understanding is that the engine RPM should increase as there is no feed back loop to tell the ECU if the compressor has engeaged or not.
The compressor relay shouldn't click if there is a pressure fault. But in the same electrical circuit will be the evaporator thermostat (normally on the ground of the compressor realy). If this has moved or gone faulty it may allow the system to work intermitantly but not long enough to start and pump the refrigerant around the system correctly. Will try and add a basic electrical diag of how the system should work.
My understanding is that the engine RPM should increase as there is no feed back loop to tell the ECU if the compressor has engeaged or not.
The compressor relay shouldn't click if there is a pressure fault. But in the same electrical circuit will be the evaporator thermostat (normally on the ground of the compressor realy). If this has moved or gone faulty it may allow the system to work intermitantly but not long enough to start and pump the refrigerant around the system correctly. Will try and add a basic electrical diag of how the system should work.
jonathant said:
I definately hear two clicks in quick succession and *sometimes* the compressor doesn't start. To confuse matters, I think I also have a leak in the system and there's little gas because I never get cold air. <sigh>
If the gas is low you will not get such cool air,but this could also simply be the fact that your heater matrix valve isn't quit fully closed when your heating control knob is set to max cold,this is very common on griffs,and some of us even use a switch to isolate the valve motor once cold is selected,as it can move of its own accord through heat soak affecting the pot!.Just the slightest opening in the matrix valve will mean you have warm air not cold.
The supply to the compressor may not be the issue it could be the earth. Not sure where the earth is taken to. You could try and ground it out somewhere else that you know is OK.
But if there is no refrigerant in the system it will still not operate.
The only way to see if the compressor is working is to give it a 12v feed and a new earth just to be on the safe side (as previously mentioned by someone else), this can done without the engine running as the clutch on the compressor will click if all is OK
But if there is no refrigerant in the system it will still not operate.
The only way to see if the compressor is working is to give it a 12v feed and a new earth just to be on the safe side (as previously mentioned by someone else), this can done without the engine running as the clutch on the compressor will click if all is OK
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