Air Con compressor turns off while driving

[schoppa]

Hi,

hot weather is coming up over here and today I made a longer trip with the 260. I turned the air con on (AUTO mode, 18 degrees) and for about 50 miles on the highway with 75 miles the inside temperature was fine and cold. Suddenly the temperature inside the car got higher, really hot air came out of the outlet nozzles in the front. I switched to ECO mode, still hot air. I turned the air con off and on again, still hot air. I stopped the car for a few minutes turned the engine off, checked the fuses and started again: air con was working fine, cold air, driver happy :). After 10 further miles again HOT air. I turned the air con off. After a short fuel break the air con was working fine again. It seems that turning the engine off and on again "fixes" the problem for a while. This is the only reproducable behaviour I could figure out today. Any ideas?

Ciao from Germany
Marcus

[colintf]

Hope you get it sorted Marcus :thumb

[Herman]

Pressure switch in the aircon circuit switching the system off?

Once cooled down or after a short stop, pressure back to normal until used for some time again.

[pessling]

sounds like the valve, you need a black olive valve, think mentioned before that even with the aircon on there is too much heat coming through as the valve is leaking by even in the close position when cold is selected

[Herman]

sounds like the valve, you need a black olive valve, think mentioned before that even with the aircon on there is too much heat coming through as the valve is leaking by even in the close position when cold is selected

Doesn't explain why it's fine after a short stop when the engine is still warm but can't rule it out either.

Marcus, also have a look here https://www.two-sixties.co.uk/mgoc260/html/f0rum/showthread.php?7615-How-to-run-the-ATC-(Climate-Control)-Diagnostics-checks

[WNJ516]

I 've had a similar problem, changed the heater water valve, and all was ok. What I would do is when you next get that problem, check the pipes from your water heater valve in the plenium before blaming the aircon. The valve was closed for heating but passing hot water into the heater matrix, I opened up my valve which was a year old I found one of the rubber seals had split, so am looking for a supplier of those seals, after all their only rubber but used in a lot of similar 2 way automotive heater valves , but have not found one yet, the valves are made in Mexico I believe, but can't find the rubber seal supplier.

[schoppa]

Hi,

before driving home from work today, I did the AC diagnostic check and it showed FC 00 = no error. After 5 miles, AC set to AUTO, again hot air. :( I stopped her for a short "beer upload" for the driver and the AC was working fine again. Awaiting a fail I stopped again and decided to use my OBD2 adapter (I use a China import with Android Torque). The AC was working fine all the way back home and did not fail. Some other "unknown errors" came up, but I think nothing which is AC related. Because a engine "off and on again" fixes the fail temporarily, could an electronic fail be the problem?

Ciao
Marcus

[torque2me]

sounds like the valve, you need a black olive valve, think mentioned before that even with the aircon on there is too much heat coming through as the valve is leaking by even in the close position when cold is selected

Peter,

I have the same symptons as the original poster - hot air in summer. However, I do not have air con (as far as I know) but climate control.

Does the black olive solution apply to the last few models as I believe the factory was supposed to have upgraded the valve?


Kev

[Nich]

Hi Kev,

If you returned your questionnaire and became a full member you could find the answers to all of your questions yourself. We are here to help but the forum does rely on everyone contributing, that's the idea of a forum, not just continually asking questions without making any contribution whatsoever.

Most of the queries you have had have already been covered and the answers are readily available to full members of this forum. It's not as if it is going to cost you, as long as you are already a member of the MGOC and own a 260/R75 V8 then all you have to do is return your questionnaire. Given the time you have spent typing up posts asking for information in the public section, I would have thought that completing one of the questionnaires you have been sent and returning it would have been a very simple straightforward process.

Be nice to see you join up, I think you would be amazed by the amount of information available to you

Nich.

[schoppa]

Hi,

260 was at MGOC workshop to check the AC. The T4 diagnostic test to cycle heating system didn't find anything and at the day she was there, the AC was working ;) They checked and lubricated the heater control valve and checked AC pump operation. Sadly the problem with the AC is still there. When we drove to Silverstone it worked fine in auto mode all the way until we made a stop for 30 minutes to buy some things for barbecue. When starting after shopping only hot air came out, AC was on auto mode. We drove a few miles, turned off the engine and started it again with a
short break of a minute. Then the AC worked for another 20 miles, then hot air again.
On the way back to Germany today the AC worked fine in auto mode (set it to 72 °F, never toughed or changed AC setting) all the way back from Silverstone to Dover and from Dover for another 350 miles on the
motorway with 70 mph. In Germany when driving a little bit faster (90 mph) and it was about 68 °F outside the AC suddenly stopped working after a while, hot air. Stopping and restarting the car didn't help this time. After a 30 minutes coffee break the AC was working cold again. Ian from workshop recommend to change the heater valve if the AC fails again.

Cheers
Marcus

[colintf]

great to meet you at MG Live Marcus
I hope that this is easily sorted out for you and that you can join us at MGFIM :cool:

[kaiser]

I have similar unexplained incidents.
I will next time it happens, check if the fan is running. The fan is supposed to run with A/C on to cool the evaporator. I believe if the fan does not work, the AC will register high pressure and switch off.
That, however does not make a lot of sense, if it happens while the car is moving, as the ram air effect should be enough. But I would check in any case.
Another possibility is a temperature sensor malfunctioning. I have seen that happen on my other Rovers for engine temperature and outside temperature, only for them to recover at next switch off and be fine for long periods.
It is really irritating that there seems to be no good pattern to this, except getting loads and loads of stinking hot air through the fascia vents.

[NOCTURNAL]

for Marus I would say his is NOT the BO valve replacement???

I say this as he has far too long with perfect aircon, it sounds to like something is actually telling the valve to open, (so as Kaiser has suggested temperature sensor malfunction for instance...

Surely his aircon woudn'e 'good' for as long if the valve had started to deteriorate? once letting by, the valve cant repair itself, it is degenerative.

but what do I know My valve is defunct now :( lasted longer than most for an everyday use car.

Hope you get sorted Marcus.

[schoppa]

Hi,

some feedback: after a diagnostic with the T4 the thermistor evaporators came up with an error. I changed the two thermistor evaporators (part no JQC000040) and toped up cooling fluid. The AC is working fine since then. I bought an aircon ECU (B28) (part no JFW000011) for safety from smc343 on ebay too, but it really seems to be that one of the sensors was the problem. Hope that's it.

6876

Thanks a lot to all of you for your time and help to this annoying problem.

Ciao
Marcus

[colintf]

Great result Marcus :)