Air con not cooling

[Alan_M]

Sorry, another a/c post

Ok, so my a/c appears to be functioning, but not cooling. I’ve been through all the tests I can do.

Mine is a 02 cdt with a 3 speed fan (no resistor visible)

The demist test - low fan speed not working, but can enable medium? speed using Toaf or shorting pins on trinary switch.

I have one of the home charging a/c adapters with a pressure gauge which shows a pressure of 60psi with a/c off and 30psi with the a/c on (which is in the green charged zone of the gauge). Note this is on the low pressure side of the circuit. I have no way to measure high pressure circuit.

The compressor is running - can be seen and confirmed by pressure change above.

I ran the a/c with the engine fan forced to medium/high to cool condenser. The high pressure pipe became just slightly cool and the low pressure very slightly warm.

I’ve had the car 5 months and not done anything to the a/c, so as it has pressure I assume there’s no leak - so why isn’t it cooling? Should I be looking at a new condenser? Or could pump not be producing enough pressure, or will it be the expansion valve?

I realise I’m also going to need to sort fan - what are my options here?
I want to keep costs down if I can

I’ve read it’s no point buying a used 3 speed fan as all will be in same condition.
Also read replacing bushes often doesn’t work as, but as only low speed not working might I be ok?

Alternatively can I replace a 3 speed fan with a used 2 speed? If so how much needs to be modified?

I have also seen the new one done by Jules.

Thanks

[Arctic]

Originally Posted by Alan_M

Sorry, another a/c post

Ok, so my a/c appears to be functioning, but not cooling. I’ve been through all the tests I can do.

Mine is a 02 cdt with a 3 speed fan (no resistor visible)

The demist test - low fan speed not working, but can enable medium? speed using Toaf or shorting pins on trinary switch.

I have one of the home charging a/c adapters with a pressure gauge which shows a pressure of 60psi with a/c off and 30psi with the a/c on (which is in the green charged zone of the gauge). Note this is on the low pressure side of the circuit. I have no way to measure high pressure circuit.

The compressor is running - can be seen and confirmed by pressure change above.

I ran the a/c with the engine fan forced to medium/high to cool condenser. The high pressure pipe became just slightly cool and the low pressure very slightly warm.

I’ve had the car 5 months and not done anything to the a/c, so as it has pressure I assume there’s no leak - so why isn’t it cooling? Should I be looking at a new condenser? Or could pump not be producing enough pressure, or will it be the expansion valve?

I realise I’m also going to need to sort fan - what are my options here?
I want to keep costs down if I can

Hi Alan.
It sounds to me that your fan is ok to re-brush as you still have the medium working, if you do go down that road I would do it asap, so the medium brushes do not get any worse, and the low speed brush what is left of it does not damage the commutator.

The reason your A/C is not getting cold is because it runs in conjunction with the low speed of the fan, that is why the low speed wears out faster than the other brushes it gets used more

Yes you can fit a two wire 2 speed fan with a gold resistor it is plug and play, all that would need to done is to cut the cowling of the fan around the A/C joints so you do not disturb the gas in the system.

You would need to do the sane if you repair /re-brush the fan, unless you are going to disconnect the A/C pipes in which case you would have to evacuate the gas first.

[Alan_M]

Originally Posted by Arctic

Hi Alan.
It sounds to me that your fan is ok to re-brush as you still have the medium working, if you do go down that road I would do it asap, so the medium brushes do not get any worse, and the low speed brush what is left of it does not damage the commutator.

The reason your A/C is not getting cold is because it runs in conjunction with the low speed of the fan, that is why the low speed wears out faster than the other brushes it gets used more

Yes you can fit a two wire 2 speed fan with a gold resistor it is plug and play, all that would need to done is to cut the cowling of the fan around the A/C joints so you do not disturb the gas in the system.

You would need to do the sane if you repair /re-brush the fan, unless you are going to disconnect the A/C pipes in which case you would have to evacuate the gas first.

Thanks

When I ran the a/c to see if it would get cold I had the engine fan running on medium speed by shorting the two furthest apart wires on the trinary switch - wouldn’t this have provided the cooling required to the condenser to allow the a/c to work in place of the slow speed ?

[SD1too]

Originally Posted by Alan_M

... I had the engine fan running on medium speed ... wouldn’t this have provided the cooling required ...

Yes Alan it would. Your problem is most likely loss of refrigerant gas through infrequent use (your high pressure pipe should be hot).

Find a self-employed mobile independent air conditioning specialist to measure your charge professionally, remove any stored moisture and check for leaks. He'll be more expensive than the fast-fit outfits but worth every penny.

You need to restore the low speed on your 3 speed fan. You said you want to keep costs down. Fitting new brushes yourself will cost about £20 and your refurbished motor will last years if you buy them from Engineering Carbon Products Ltd. in Croydon. A two speed system will be noisier and much more expensive (as well as being unnecessary!).

Simon

[Nick Greg]

And once fixed don't forget air con is not just for summer. Use it or lose it. Good for demisting in winter etc.

[vitesse]

Not that it makes much difference, but isn’t it more likely that the OP is only able to activate high speed? I thought the low and medium speeds shared the same earth brush - from memory most of the failed three speed fans I’ve tested had neither low nor medium, but usually high speed, sometimes though not even high speed.

Not nearly as experienced as Arctic, never worked on a diesel, but on KV6 & 1.8Ts I don't cut the cowling, just release it from the non AC side and "hinge" it forwards enough to access the difficult torx holding the motor.

And from my experience there’s a good chance that you can re-brush the fan back to working condition. Of perhaps eight fans motors I’ve been able to bring five of them back to life.

Good luck

[SD1too]

Originally Posted by vitesse

... isn’t it more likely that the OP is only able to activate high speed?

Hi Mike,

High speed isn't available to the air conditioning.

Originally Posted by vitesse

I thought the low and medium speeds shared the same earth brush ...

Yes they do. According to Alan's account his fan will be running at low, not medium speed (it will have one supply and one earth brush).

Originally Posted by vitesse

... on KV6 ... I don't cut the cowling ..

I didn't either Mike. I can't remember how I did it but I did manage to keep the cowling intact.

Originally Posted by vitesse

And from my experience there’s a good chance that you can re-brush the fan back to working condition.

Absolutely there is! Agreed Mike.

Simon

[Alan_M]

Originally Posted by SD1too

Yes Alan it would. Your problem is most likely loss of refrigerant gas through infrequent use (your high pressure pipe should be hot).

Find a self-employed mobile independent air conditioning specialist to measure your charge professionally, remove any stored moisture and check for leaks. He'll be more expensive than the fast-fit outfits but worth every penny.

You need to restore the low speed on your 3 speed fan. You said you want to keep costs down. Fitting new brushes yourself will cost about £20 and your refurbished motor will last years if you buy them from Engineering Carbon Products Ltd. in Croydon. A two speed system will be noisier and much more expensive (as well as being unnecessary!).

Simon

Thanks - I will be ordering 2 sets. See further down for reason 😁

Originally Posted by Nick Greg

And once fixed don't forget air con is not just for summer. Use it or lose it. Good for demisting in winter etc.

Ive always used mine throughout the year 👍

Originally Posted by vitesse

Not that it makes much difference, but isn’t it more likely that the OP is only able to activate high speed?

And from my experience there’s a good chance that you can re-brush the fan back to working condition. Of perhaps eight fans motors I’ve been able to bring five of them back to life.

Good luck

Having re-read Jules’ post on checking the a/c system, you are correct, it is the high speed fan that is tested by shorting the connections at the trinary switch.

Originally Posted by SD1too

Hi Mike,

High speed isn't available to the air conditioning.

Yes they do. According to Alan's account his fan will be running at low, not medium speed (it will have one supply and one earth brush).

I didn't either Mike. I can't remember how I did it but I did manage to keep the cowling intact.

Absolutely there is! Agreed Mike.

Simon

The fan doesn’t run using the demist test, which I believe would be the slow speed. Also, using Toaf the fan doesn’t activate until I move the activation slider beyond half way.

I have, however, found a sort of solution - I’ve bought another R75 with working aircon, but again with 3 speed fan that doesn’t cut in straight away when a/c switched on, or with demist test. It kept cutting in and out on I assume a high speed. Hence the reason I will be ordering 2 sets of brushes to hopefully sort both fans.

[SD1too]

Originally Posted by Alan_M

Having re-read Jules’ post on checking the a/c system, you are correct, it is the high speed fan that is tested by shorting the connections at the trinary switch.

It is on a 2 speed system Alan but you haven't got that. On a 3 speed fan it's the medium speed which is triggered by the trinary switch.

As I said in my last post, the high speed of a 3 speed system is never triggered by the air conditioning, only by coolant temperature.

Simon

[Alan_M]

Originally Posted by SD1too

It is on a 2 speed system Alan but you haven't got that. On a 3 speed fan it's the medium speed which is triggered by the trinary switch.

As I said in my last post, the high speed of a 3 speed system is never triggered by the air conditioning, only by coolant temperature.

Simon

Thanks, at least that would hopefully suggest rebuilding the fans has more chance of working.