Help with air con relay in engine bay

[macafee2]

April I had the air con re-assed
Hardly used the car since.
Today, no cooling via air con.

Took it to garage to check for a leak, nothing found.
They have re-gassed it and used apparently a lot of leak dye. I'll use the car over the weekend and take it back to them next week see if they can spot a leak.

Mechanic said that the engine bay relay was stuck. This caused the compressor to run more then it should, heating the gas and perhaps it has vented via a pressure release valve. Have you know this before, I think the relay part number is YWB0040 item 14 on this link

https://rimmerbros.com/Item--i-GRID001619


what causes the relay to activate and deactivate and what does the relay control?

macafee2

[SD1too]

Ian; you're raised a lot of points so I'll deal with them individually.

Originally Posted by macafee2

Took it to garage to check for a leak, nothing found.

That depends upon the method used to detect a leak. Being a garage and not an air conditioning specialist I suspect that they just ran their automatic machine to see if a vacuum was held. I know from expensive experience that this is an unreliable method of detecting leaks.

They have re-gassed it and used apparently a lot of leak dye. I'll use the car over the weekend and take it back to them next week see if they can spot a leak.

Only do that if they have UV test equipment. You'd be better off finding a mobile specialist although obviously they'll be very busy at the moment!

Mechanic said that the engine bay relay was stuck.

That will be the compressor clutch relay, R7. You can substitute the fog lamp relay (R6) to check whether or not he's telling you porkies. However, bear in mind that R7 should remain energised whenever the air conditioning is switched on. Your mechanic's comment suggests that he doesn't know that the compressor is a variable displacement type.

... and perhaps it has vented via a pressure release valve.

If your mechanic spoke those words then do not go back to him because he knows nothing about air conditioning.

what causes the relay to activate and deactivate and what does the relay control?

It activates when you switch on the air conditioning.
It deactivates when either the low or high pressure trinary switch operates (indicating a fault).
The relay controls the engagement of the compressor clutch. This transmits drive from the engine into the compressor.

In summary Ian, go to a self-employed mobile specialist who will do the job properly for you.

Simon

[macafee2]

Originally Posted by SD1too

Ian; you're raised a lot of points so I'll deal with them individually.

That depends upon the method used to detect a leak. Being a garage and not an air conditioning specialist I suspect that they just ran their automatic machine to see if a vacuum was held. I know from expensive experience that this is an unreliable method of detecting leaks.

Only do that if they have UV test equipment. You'd be better off finding a mobile specialist although obviously they'll be very busy at the moment!

That will be the compressor clutch relay, R7. You can substitute the fog lamp relay (R6) to check whether or not he's telling you porkies.

If your mechanic spoke those words then do not go back to him because he knows nothing about air conditioning.

It activates when you switch on the air conditioning.
It deactivates when either the low or high pressure trinary switch operates (indicating a fault).
The relay controls the engagement of the compressor clutch. This transmits drive from the engine into the compressor.

In summary Ian, go to a self-employed mobile specialist who will do the job properly for you.

Simon

cheers Simon, I hope that as a main dealer they would have uv equipment to check.


If the relay does not deactivate, what happens? The compressor carries on running but what else?

Is there a way for me to make it deactivate or test it deactivates such as increasing the temperature control.

macafee2

[SD1too]

Originally Posted by macafee2

cheers Simon, I hope that as a main dealer they would have uv equipment to check.

I'd say that's an unsafe assumption Ian. Most main dealers sub-contract air conditioning work that's any more complicated than a re-gas.

If the relay does not deactivate, what happens? The compressor carries on running but what else?

You need to check the claim that the relay is "stuck". Speculation on the basis of an unproven diagnosis is pointless.

Is there a way for me to make it deactivate or test it deactivates such as increasing the temperature control.

The temperature setting will have no effect. You can check that the relay contacts break by switching to 'Econ' mode or by testing it electrically according to your second thread.

Simon