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Discussion Starter · #1 ·
Hey guys could use some help I have the 2007 zetec mk4 mondeo. Took car to get regas twice now pressure was fine but no cold air pumping. Had air con pump changes but made no difference seems the relay not getting any current. I ordered a relay but tests I done already are showing it is fine. When new relay comes and if doesn't work where else can the fault be. Any common places wire can break or unusual thing that can interfere I would really appreciate help because I can't afford to to take to garage again to have then spend a hour searching for fault then telling I have to book it in again to fix issue
 

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I seem to remember a purple wire going to the aircon fan being a common fault, might be worth a search on here for that.
 

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The way these systems work is that the Air con relay is switched by a pressure sensor / switch - i.e. it disables your air con if your system pressure is too low - to protect the compressor.
You say you've had the system regassed twice. Where ever you've had this done will have been required by law to do a full pressure / leak test of your system, since it is illegal to fill a leaking system
Having said that, I had the system on my 'other' car regassed a number of years ago and all tests looked OK, and the air con worked fine afterwards - for about a fortnight. It was only when I began the process of removing the engine for a complete overhaul that I discovered that my condensor was toast. The bottom of it literally disintegrated as I removed it.
There are a number of checks that you should be able to do.
Firstly, if you disconnect the pressure sensor, you should be able to short the terminals in the connector which will mimick the pressure switch circuit closing and engaing the relay. If you hear the relay switching, you will know the issue is related to the pressure switch or a system pressure issue - and I would then urge you to first have the system pressure tested, as if the switch itself is at fault, you will have to have the system drained in order to replace it.
If the relay doesn't switch, then it's likely a break in the wiring or a bad connection somewhere.
 

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The A/C relay (pin 2) is likely to have lost its control from the engine control unit, usually a broken wire between ECU (PCM) and relay
 

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Discussion Starter · #5 ·
The way these systems work is that the Air con relay is switched by a pressure sensor / switch - i.e. it disables your air con if your system pressure is too low - to protect the compressor.
You say you've had the system regassed twice. Where ever you've had this done will have been required by law to do a full pressure / leak test of your system, since it is illegal to fill a leaking system
Having said that, I had the system on my 'other' car regassed a number of years ago and all tests looked OK, and the air con worked fine afterwards - for about a fortnight. It was only when I began the process of removing the engine for a complete overhaul that I discovered that my condensor was toast. The bottom of it literally disintegrated as I removed it.
There are a number of checks that you should be able to do.
Firstly, if you disconnect the pressure sensor, you should be able to short the terminals in the connector which will mimick the pressure switch circuit closing and engaing the relay. If you hear the relay switching, you will know the issue is related to the pressure switch or a system pressure issue - and I would then urge you to first have the system pressure tested, as if the switch itself is at fault, you will have to have the system drained in order to replace it.
If the relay doesn't switch, then it's likely a break in the wiring or a bad connection somewhere.
Where is the aircon pressure sensor located>? Struggling to find details on wiring for my car
 

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Simple test of purple wire is leave car on tickover after a run to raise engine temp, if fan comes on then purple wire is ok
 
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