Air Conditioning Question

[Odd Job]

Hi everyone,

Ive got a weird thing going on with my air conditioning, and I wonder if anyone can offer any help before I take it to a garage and potentially get ripped off.

Firstly, I've had, and driven plenty of cars with A/C fitted. This is the first time I've come across this, I'm no expert. But I know the basics of how A/C works etc.

I currently have also a MG ZS which has fully working A/C , my ZT is my replacement for the ZS which is up for sale.
I digress.

OK.
So, my ZT after roughly about 20 mins with the A/C on only slightly cools down the air coming out of the vents.
I was hopeful that all it needed was a re-gas, but it does have a "wuring" noise when it's switched on as well.
A work college kindly lent me a DIY A/C re-gas kit this evening which I used.

Initially I thought it hadnt worked, but after taking the car out for a run, the air out of the vents is quite a bit cooler.

But.....

When i stop at a junction or traffic lights etc, there is noise that starts up, like a whooshing noise, sort of like the sound of air traveling through a pipe. After you sit for quite a while the A/C pump switches itself off and you get atmospheric temperature air out of the vents.
When you set off driving, the A/C kicks in again and you get cold air.
Pull up. Whooshing noise. A/C stops. Warm air comes out of the vents, pull away. A/C kicks in etc, etc, etc

Does anyone have any ideas?

[SCP440]

DIY A/C refill is a bad idea, you don't pull a vacuum so you could potentially still have moisture in the system.

The only way to do it is to drain the system, pressure test and them draw a vacuum and then refill with the correct amount of refrigerant.

Get a local mobile A/C engineer to visit you and I am sure they will quickly work out once the system has been correctly serviced what the problem is.

[Odd Job]

That's a fair comment.

I only really did the DIY re-gas as I wasnt sure if the system actually worked.

I have proved it does, of a fashion, but I do agree with what you have said.
I just wondered if anyone had come across the whooshing sound I mentioned before?
With the A/C pump cutting in and out instead of staying engaged I wondered if the pump might be on the way out?

[T-Cut]

I suspect your radiator cooling fan's low speed has failed. That's why it works when driving and gives up when stationary. It's an extreme case by the sound of it. The system shutting down indicates significant overheat/overpressure is developing, which the higher speed fan can't cope with. You may have a condenser problem to complicate it all. Basically, the A/C system isn't getting sufficient condensation in the loop to run properly.

So, check your low speed by doing the 'Demist Test'. If that confirms lack of low speed cooling, fix that and try again. If the system still doesn't operate as it should I'd check the condenser mounted on the front bottom of the engine radiator (bumper off job). These condensers are very prone to loss of the fins.

The whooshing sound is from the thermal transfer valve attempting to feed gas into the system to cope with the cooling demand you've set. It's often due to insufficient refrigerant, but a failing condenser has the saame effect.

I'd try to get it running with the gas left as it is. If there's any problems after fixing the suspected condensation bits (low speed fan, condenser) maybe a 'pro' regas is on the cards.

TC

[Odd Job]

Wow!

Thanks!
Thats plenty to go at.

[Dawn]

My condenser was so rotten it simply fell apart when touched!

[T-Cut]

And once again folks - - -





- - - a picture paints thousand words.


TC

[Odd Job]

I'll have a look at mine!

Was it still holding gas??

[Odd Job]

Originally Posted by T-Cut

I suspect your radiator cooling fan's low speed has failed. That's why it works when driving and gives up when stationary. It's an extreme case by the sound of it. The system shutting down indicates significant overheat/overpressure is developing, which the higher speed fan can't cope with. You may have a condenser problem to complicate it all. Basically, the A/C system isn't getting sufficient condensation in the loop to run properly.

So, check your low speed by doing the 'Demist Test'. If that confirms lack of low speed cooling, fix that and try again. If the system still doesn't operate as it should I'd check the condenser mounted on the front bottom of the engine radiator (bumper off job). These condensers are very prone to loss of the fins.

The whooshing sound is from the thermal transfer valve attempting to feed gas into the system to cope with the cooling demand you've set. It's often due to insufficient refrigerant, but a failing condenser has the saame effect.

I'd try to get it running with the gas left as it is. If there's any problems after fixing the suspected condensation bits (low speed fan, condenser) maybe a 'pro' regas is on the cards.

TC

It does appear that the low speed isnt working on my fan.
So, how do I sort that out?
What do I need to get it going again?
The fan itself works, but like you say, it's not working at low speed. Is there a "gizmo" that controls the speed that I can replace?

Thanks

Richard

[trikey]

Do you have a silver resistor fitted to the fan (Look through the grille, it sits about 2 O'clock when you look at the fan)