Air con cuts out in very hot weather

[geoff46]

Hi all, I’m having some intermittent air con problems and would appreciate some advice. Got a 2000 diesel face lift Bongo with climate control, located in St Albans. Under normal conditions the air con works fine, but when it gets hot outside, like now, the problem appears. It works fine when you first start up, but once the engine gets up to temperature the air con cooling cuts out. Blowers keep running but it’s just recirculating warm air. Coolant temp gauge sits happily at 11 o’clock (for what that’s worth) and no warning lights come on. Radiator fans come on as they should as soon as the air con is switched on. I’ve had the air con system checked to see if it needs re-gassing, which it doesn’t. I was also advised to check that the scavenger fan was working. It doesn’t seem to be coming on, but from what I’ve read that isn’t unusual. I’ve tested it by shorting the pins of the air temp sensor connector by the handbrake and it came on as it should. Leaving it running constantly didn’t stop the air con from cutting out. Any ideas? I am wondering if the air temp sensor has any role in governing the air con system in addition to the scavenger fan and thinking maybe should try replacing it? Thanks in advance for any help.

[g8dhe]

The scavenger fan has no involvement with the air con at all. The only sensor for the scavenger fan is the thermistor mounted under the handbrake poking in to the engine housing, it only comes on when the air above the engine gets hot, normally when the vehicle is static or slow moving and the air flow is insufficient to keep the temperature down.

As to the air con, not sure I have ever heard of a fault like that before, is the compressor continuing to run ? There is a belt that drives the spindle which then has a magnetically operated clutch to connect it the compressor itself, this is controlled by the climate control module along with the pressure sensor to make sure there is refrigerant in the system as well.

[cwilliams255]

As the aircon works most of the time and everything is static except the compressor it does seem like the compressor clutch is maybe failing to engage in hot weather. It’s pretty easy to check as you should be able to hear / feel it engage when you turn AC on and off (at least in mine you can)

Only time I experienced something similar was due to a gas leak, was fine until a really hot day where it ended up below engagement value of sensor. However as you’ve had it checked then it seems unlikely - did they tell you how much gas was present?

[geoff46]

Thanks for the info guys. I'll check out the clutch. I wasn't told how much gas was is the system, just that it wasn't a problem. I'll go back to the garage and see if they have a record of it.

[Northern Bongolow]

You can usually improve things by checking the airflow through the condenser rad, mine was filled with weird Japanese dragon flies,they were all holding hands and blocking throughput of air,
Strip the front off the heater unit under the bonnet till you come to the condenser, clean out with a soft brush etc you will notice a difference.
Also check the front sensor on the dash, this has a little fan in it, it gets blocked, quick blow out can help.

[geoff46]

Will do this also.

Regarding the clutch I tested it from cold yesterday. When switching the air con on and off you can hear a click from the compressor which I assume is the clutch engaging and disengaging. However once the engine was hot and the air con had stopped working then the click also stopped.

[g8dhe]

Well other than checking the voltage on the connectors that would rather point to the problem or manually triggering the relay when its hot to see if its the ECU signal that is not operating it. The clutch solenoid is G3-03 lower left and the relay G3-02 by earthing the Yellow/White (Y/W) would cause the relay to operate, if it does and the clutch comes in then it would point to being back towards the ECU.

[geoff46]

Thanks Geoff, I'd just like to check my understanding.

When the air con has stopped cooling:
1. Check the voltage on the connector at the compressor - if that's ok then the fault is likely to be the clutch solenoid
2. If not ok then earth Y/W wire at the relay. If the relay operates then the fault is likely to be the ECU, if it doesn't then the fault is likely to be the relay

Have I got it right?

A couple of stupid questions
1. The compressor connector is on the single wire running to the compressor over the top of alternator?
2. Where is the air con relay physically located? I think it's one of the 4 on the passenger side wing under the bonnet. I've had a good search online but can't find anything that shows which one it is.

I'll need the weather to improve before I can do this!

Thanks again.

[g8dhe]

When the air con has stopped cooling:
1. Check the voltage on the connector at the compressor - if that's ok then the fault is likely to be the clutch solenoid
2. If not ok then earth Y/W wire at the relay. If the relay operates then the fault is likely to be the ECU, if it doesn't then the fault is likely to be the relay

Have I got it right?

Yes

1. The compressor connector is on the single wire running to the compressor over the top of alternator?
2. Where is the air con relay physically located?

Yes and check the next page on the diagrams, positions of each device shown on vehicle layout.

[geoff46]

Found the relay. Just need to wait for the weather to improve then I'll do the testing. I'll let you know how I get on. Thanks for all the help so far.

[geoff46]

Right, test done. When the aircon cut out there was still voltage at the connector to the compressor, so looks like faulty clutch solenoid. Do you know if these are serviceable (have found the diagram on Lush Projects), or am I best to get a new compressor? Thanks.

[g8dhe]

I've not heard of anyone affecting a repair, a recent attempt on FB ended up with the compressor damaged in removing the clutch!

[geoff46]

Ok, new it is. Update to follow.

[rita]

As a matter of interest was the system re gassed .