Discussion
Does anyone have much experience with a/c I just can’t seem to get mine working well.
The system is fully charged and does work but not for long and the switch on the compressor keeps turning it off.
I have checked the Trinary switch that seems to be ok will cut the fans in as needed. I also have a therister switch in the glove box that will also put one fan on and will cut the compressor and fan at the same time.
Ambient temperature here today Is about 25c it will cool the air to around 13c then it cuts off temps will go up to 25c at the vents then after a while the pump kicks back in cools to 13 for a short while then cuts off again. It seems to be always the switch on the compressor that cuts out the clutch.
Any help would be great
Chris
The system is fully charged and does work but not for long and the switch on the compressor keeps turning it off.
I have checked the Trinary switch that seems to be ok will cut the fans in as needed. I also have a therister switch in the glove box that will also put one fan on and will cut the compressor and fan at the same time.
Ambient temperature here today Is about 25c it will cool the air to around 13c then it cuts off temps will go up to 25c at the vents then after a while the pump kicks back in cools to 13 for a short while then cuts off again. It seems to be always the switch on the compressor that cuts out the clutch.
Any help would be great
Chris
The most common cause of switching on and off is a blockage at the receiver/drier - the filter. When recharging an older system its always advisable to replace the drier first as a system that has been stood for a while will accumulate moisture. They are cheap to buy too:
https://tvr-parts.com/tvr-parts/part-details/tvr-p...
It will mean recharging the system again though.
https://tvr-parts.com/tvr-parts/part-details/tvr-p...
It will mean recharging the system again though.
This link should help - its clearer than I can write it with a list of symptoms.
https://www.yourmechanic.com/article/symptoms-of-a...
https://www.yourmechanic.com/article/symptoms-of-a...
Something in the back of my mind is telling me that the pressure switch that's mounted on the compressor is its life saver should other pressure switches fail or there be a blockage somewhere, I think the compressor pressure switch senses for loss of pressure at the compressor and switches the clutch off no matter what else is happening around the system
The above relates to systems that have a high and low pressure switch fitted elsewhere
I think the above is correct but could be wrong
The above relates to systems that have a high and low pressure switch fitted elsewhere
I think the above is correct but could be wrong
Thanks for the link. The air con works great when it’s working and the switching on and off is not rapid in fact it will run for a good few minutes then cut off agian for a good few minutes.
Using a temp
Probe in the vent air temp without A/C on 26c turn on the A/C and it quickly cools to around 10c then cuts off the temps will rise back up to 26c and stay there for a minute or so and then the clutch engages again and it cools back down.
There looks to have been some work done on it and I know it had a new compressor not too long ago. There is some none original wireing from the variable thermistor switch behind the glovebox that goes to one radiator fan switching it on permanently while the a/c is working.
So should a radiator fan be on permanently when the A/C is on?
Using a temp
Probe in the vent air temp without A/C on 26c turn on the A/C and it quickly cools to around 10c then cuts off the temps will rise back up to 26c and stay there for a minute or so and then the clutch engages again and it cools back down.
There looks to have been some work done on it and I know it had a new compressor not too long ago. There is some none original wireing from the variable thermistor switch behind the glovebox that goes to one radiator fan switching it on permanently while the a/c is working.
So should a radiator fan be on permanently when the A/C is on?
chris52 said:
Does anyone have much experience with a/c I just can’t seem to get mine working well.
The system is fully charged and does work but not for long and the switch on the compressor keeps turning it off.
I have checked the Trinary switch that seems to be ok will cut the fans in as needed. I also have a therister switch in the glove box that will also put one fan on and will cut the compressor and fan at the same time.
Ambient temperature here today Is about 25c it will cool the air to around 13c then it cuts off temps will go up to 25c at the vents then after a while the pump kicks back in cools to 13 for a short while then cuts off again. It seems to be always the switch on the compressor that cuts out the clutch.
Any help would be great
Chris
The system is fully charged and does work but not for long and the switch on the compressor keeps turning it off.
I have checked the Trinary switch that seems to be ok will cut the fans in as needed. I also have a therister switch in the glove box that will also put one fan on and will cut the compressor and fan at the same time.
Ambient temperature here today Is about 25c it will cool the air to around 13c then it cuts off temps will go up to 25c at the vents then after a while the pump kicks back in cools to 13 for a short while then cuts off again. It seems to be always the switch on the compressor that cuts out the clutch.
Any help would be great
Chris
chris52 said:
Does anyone know the correct charge For the A/C ?
Cheers
How do you know the system is fully charged?Cheers
See NZ fan's answer in this old thread for weight - 1200g and 150ml of oil.
https://www.pistonheads.com/gassing/topic.asp?h=0&...
https://www.pistonheads.com/gassing/topic.asp?h=0&...
Hi,
the original a/c system (which is basically the rover system) has a few compressor cut off switches,
trinary switch on receiver drier will cut compressor due to low pressure or high system pressure,
thermostatic switch (bulb in evaporator coil) will cut compressor when evaporator gets too cold to stop it icing up,
thermal switch (on compressor) will cut compressor if compressor gets too hot.
The system has a logic relay and a compressor relay and is ultimately switched by the ECU earthing the compressor relay, the official rover manual has a fully detailed chapter on the a/c system.
The trinary switch will activate rad fans to control system pressure, on when pressure high, off when pressure falls back into range, the TVR system was never wired to have a rad fan all the time.
If gas charge weight is wrong, to much shuts off the due to high system pressure, to little shuts off due to low system pressure. Too low a gas charge can also cause the evaporator to run too low gas temperatures causing icing and thus cutting out.
TVR gas charge weight I have seen quoted any were from 850 gms to 1200 gms, the Rover Discovery is 900 +/- 50 gms. I have no engine bay label but I have seen them in other engine bay pictures, this would be helpful. A competent a/c specialist should be able to determine best charge weight.
Note, make sure heater valve is fully closed when running a/c (actually check pipe temps, as valve can fail and allow bypassing), otherwise the cold air will then pick up heat as it also passes over the car heater radiator before exiting the car vents. Also make sure you have the air recirc switch on, this will help with cabin cooling.
Ozstyle
the original a/c system (which is basically the rover system) has a few compressor cut off switches,
trinary switch on receiver drier will cut compressor due to low pressure or high system pressure,
thermostatic switch (bulb in evaporator coil) will cut compressor when evaporator gets too cold to stop it icing up,
thermal switch (on compressor) will cut compressor if compressor gets too hot.
The system has a logic relay and a compressor relay and is ultimately switched by the ECU earthing the compressor relay, the official rover manual has a fully detailed chapter on the a/c system.
The trinary switch will activate rad fans to control system pressure, on when pressure high, off when pressure falls back into range, the TVR system was never wired to have a rad fan all the time.
If gas charge weight is wrong, to much shuts off the due to high system pressure, to little shuts off due to low system pressure. Too low a gas charge can also cause the evaporator to run too low gas temperatures causing icing and thus cutting out.
TVR gas charge weight I have seen quoted any were from 850 gms to 1200 gms, the Rover Discovery is 900 +/- 50 gms. I have no engine bay label but I have seen them in other engine bay pictures, this would be helpful. A competent a/c specialist should be able to determine best charge weight.
Note, make sure heater valve is fully closed when running a/c (actually check pipe temps, as valve can fail and allow bypassing), otherwise the cold air will then pick up heat as it also passes over the car heater radiator before exiting the car vents. Also make sure you have the air recirc switch on, this will help with cabin cooling.
Ozstyle
The problem is that the weight figures that are being quoted don't help much, the OP has asked about pressure and pressure is what the job's all about
The following seems to give good information http://rechargeac.com/how-to/ac-system-pressure-ch...
Here is another good bit of help https://www.buyautoparts.com/howto/ac-pressure-rea...
The following seems to give good information http://rechargeac.com/how-to/ac-system-pressure-ch...
Here is another good bit of help https://www.buyautoparts.com/howto/ac-pressure-rea...
Edited by Penelope Stopit on Monday 25th June 08:48
The symptoms you are describing point to the expansion valve that is fitted to the back of the heater box.
I had exactly the same thing on mine, the whole system was newly built and retrofitted from scratch so I knew all the components were new and should be working properly.
Like you it would work, then turn off then work and it was driving me nuts. I checked everything and then took it to an ac tech and he was convinced I had a faulty compressor. So he rewired it so that the overheat cut out was out of the loop, same thing, it would work, stop, work etc.
So I tried a different ac tech and after an afternoon of scratching heads he suspected the expansion valve, even though it was also brand new.
Turns out that during the fitting and testing stage, where gas was repeatedly put in after it would leak out, that if the gas was not properly taken out each time as was topped up, that oil would stay in the system and build up that is how the expansion valve was blocked. This caused the pipework and gas to get very hot and this would cause the cutout in the system to turn off the coil that pulls the compressor pulley in.
He changed it, cheap part, difficult job though through the little door under the afm, and my ac has worked faultlessly every day here since, and in 30-40deg heat.
I had exactly the same thing on mine, the whole system was newly built and retrofitted from scratch so I knew all the components were new and should be working properly.
Like you it would work, then turn off then work and it was driving me nuts. I checked everything and then took it to an ac tech and he was convinced I had a faulty compressor. So he rewired it so that the overheat cut out was out of the loop, same thing, it would work, stop, work etc.
So I tried a different ac tech and after an afternoon of scratching heads he suspected the expansion valve, even though it was also brand new.
Turns out that during the fitting and testing stage, where gas was repeatedly put in after it would leak out, that if the gas was not properly taken out each time as was topped up, that oil would stay in the system and build up that is how the expansion valve was blocked. This caused the pipework and gas to get very hot and this would cause the cutout in the system to turn off the coil that pulls the compressor pulley in.
He changed it, cheap part, difficult job though through the little door under the afm, and my ac has worked faultlessly every day here since, and in 30-40deg heat.
Many thanks for the help I think I have sorted it. Basically the fans on the radiator were the wrong ones. When I rebuilt the front end I put the 27a fans on I have now changed these for the 45a ones and now the a/c runs continuously today outside temps around 24c air coming from the vents without a/c on around 28c ( with a bit of heat soak from the engine pipes coming from the heater box cold) a/c on cools it down to around 10c at the vents when the engine bay is cold it will cool it down to 5c I could really do with getting the recirculation door opening properly as this will help as well but every time I adjust it to stay open the next time I look it’s closed again so may just prop it open permanently for now.
Great news you sorted it.
The recirculation flap is the next thing I have to sort out as I didn't have one on this non ac car and could not find a donor car to take it out.
I am not sure if I could fabricate one of my own as I haven't seen an original one, so once I find one my installation will be complete.
The recirculation flap is the next thing I have to sort out as I didn't have one on this non ac car and could not find a donor car to take it out.
I am not sure if I could fabricate one of my own as I haven't seen an original one, so once I find one my installation will be complete.
jazzdude said:
Great news you sorted it.
The recirculation flap is the next thing I have to sort out as I didn't have one on this non ac car and could not find a donor car to take it out.
I am not sure if I could fabricate one of my own as I haven't seen an original one, so once I find one my installation will be complete.
Well I thought I had it sorted sat in the garage with the air con on it works perfectly take it out for a run and it’s ok for the first 10 mins or so nice cool air but gradually heats up and up with the pump only cutting in briefly so will have a look at the valve. I have the little cover off I guess this is the part https://tvr-parts.com/tvr-parts/part-details/tvr-p... will get one ordered and see if it cures it.The recirculation flap is the next thing I have to sort out as I didn't have one on this non ac car and could not find a donor car to take it out.
I am not sure if I could fabricate one of my own as I haven't seen an original one, so once I find one my installation will be complete.
Chris
Edited by chris52 on Saturday 30th June 16:54
Went out in the car Sunday air con on worked for a short while then gets warm again this happened all the way there about 80 miles. On the way back the A/C worked fine and it has ever since temps down to as low as 3c at the vents and never above 9c but does cycle between these two so may need a little tweaking still.
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