A/C question need help

[Zaki84]

Got some issues with a/c. When I start car,and turn aircon on,fans are working but a/c compressor doesn’t kick in. When I connect aircon compressor directly to battery it works. Any ideas? What could be issue?


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[feenix74]

Golf Mk3 aircon compressors are beltdriven, so what do you mean by it works when you connect it directly to battery? Do you mean that the A/C clutch solonoid works to engage the clutch to drive the compressor? If so, check that there is not a break in the wiring to aircon compressor.

[Zaki84]

Golf Mk3 aircon compressors are beltdriven, so what do you mean by it works when you connect it directly to battery? Do you mean that the A/C clutch solonoid works to engage the clutch to drive the compressor? If so, check that there is not a break in the wiring to aircon compressor.

Yea,clutch engages in compressor when directly connected. And cold air starts blowing.


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[feenix74]

I am not an auto electrician but I would deduce that means you have a break somewhere in the wiring to the aircon compressor (ie you have proven the solonoid for the clutch to the aircon compressor engages the clutch, you have proven that the compressor itself works to produce chilled refrigerant). However, if it does not work without direct power, then somewhere between the aircon switch on the centre console and the solonoid the electrical signal to engage the clutch is being interrupted.

[Zaki84]

I am not an auto electrician but I would deduce that means you have a break somewhere in the wiring to the aircon compressor (ie you have proven the solonoid for the clutch to the aircon compressor engages the clutch, you have proven that the compressor itself works to produce chilled refrigerant). However, if it does not work without direct power, then somewhere between the aircon switch on the centre console and the solonoid the electrical signal to engage the clutch is being interrupted.

Could it be fcm? Fan control module


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[feenix74]

Could be but you said that the fans are working but the aircon does not kick-in. That leads me to believe compressor clutch solonoid, which you have proven works, which leads me to believe possibly the wiring to the clutch solonoid. Can you put a multi-meter on the connector to the aircon compressor and get a reading (or a change in reading) when you turn on the aircon switch?

[Bora Sport]

The system has both a high pressure and a low pressure cut out switch to protect the system when the gas level gets low. Perhaps there is enough to produce cool air when turned on full time by direct current but not enough for it to operate normally and cycle. I would be getting the car to an air conditioning specialist to check it out.

[Zaki84]

Could be but you said that the fans are working but the aircon does not kick-in. That leads me to believe compressor clutch solonoid, which you have proven works, which leads me to believe possibly the wiring to the clutch solonoid. Can you put a multi-meter on the connector to the aircon compressor and get a reading (or a change in reading) when you turn on the aircon switch?

Took plug off fcm and getting 12v when aircon is on. Che led plug that goes to compressor nothing. Followed wires there is one plug before compressor and nothing there too.


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[feenix74]

A break in the wiring between the FCM and that one plug before the compressor? It could be the FCM but I would think that the aircon fans would not work if the FCM was dead. You could try replacing the FCM to see if that makes a difference but if that does not then I would believe a break in the wiring between the FCM and that one plug before the compressor.

[Zaki84]

A break in the wiring between the FCM and that one plug before the compressor? It could be the FCM but I would think that the aircon fans would not work if the FCM was dead. You could try replacing the FCM to see if that makes a difference but if that does not then I would believe a break in the wiring between the FCM and that one plug before the compressor.

Aircon worked 2 months ago. So I’m assuming should be wires. I’ll see I’m Getting new fcm,and I’ll see if that fixes it


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[Zaki84]

A break in the wiring between the FCM and that one plug before the compressor? It could be the FCM but I would think that the aircon fans would not work if the FCM was dead. You could try replacing the FCM to see if that makes a difference but if that does not then I would believe a break in the wiring between the FCM and that one plug before the compressor.

New fcm didn’t fix it. Checked wires from compressor to that middle plug it’s all good. From that middle plug to fcm all good. No break in wires. Is there pressure switch somewhere? Read few posts on forums.


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[feenix74]

Your problem has exceed my limited auto electrical knowledge.

I would believe that Bora Sport is correct that the system has both high and low pressure cutouts. I agree with Bora Sport's recommendation, that now you have exhausted the obvious causes of the issue it is probably time to get an auto aircon specialist/auto electrican to have a look at it.

Good luck, I wish I could have been of more assistance.