A/c Electrics

October 19, 2011

HI GUYS, HAVING A PROBLEM WITH A/C ELECTRICS ON 2008 MK6 VIGO 3LTR.

A/C FAILS TO COME ON,

NO ILLUMINATION ON A/C SWITCH,

NO POWER TO A/C SWITCH,

NO POWER TO CONNECTOR OF A/C SWITCH CABLE BEHIND DASH,

ALL FUSES UNDER BONNET PASSENGER SIDE FUSE COVER TEST OK,

ALL FUSES UNDER STEERING WHEEL TEST OK,

ALL FUSES BEHIND GLOVE BOX TEST OK.

ANY IDEAS, I DON'T HAVE OWNERS MANUAL THEREFORE THERE MAY BE A FUSE THAT I DON'T KNOW ABOUT

October 19, 2011

Hi Daragh,

Well, it's been a few years since I worked on Automotive A/C......and certainly not on a 2008 vehicle, so, I may be way off beam here: But here goes!

First stop is to confirm if your system has any gas in ..unfortunately, with your gas (R134a) you will need a set of gauges with special access valves/connectors. These are not cheap.

On older cars, all the power for the A/C system had to come through a series of interlocks...safety switches if you like...these were pressure switches fitted in the low pressure (Suction) & high pressure (Discharge) lines.....they guarded against the obvious "Pressure Too Low" & "Too High" Scenarios....The low pressure switch also guarded against loss of refrigerant, which obviously is not desirable!

But, identify the suction line: It is the bigger diameter of the two. If this switch is 'open'...it may be that you have lost the gas.

On more modern cars it gets more complicated: There are sensors for just about every scenario you can think of! But,I would suggest you continuity check the various pressure switches you can identify in the gas lines.....but remember,one switch in the HIGH/DISCHARGE side will be to turn the condenser fan ON, so will be open under these conditions.....and it may be part of a three way switch.(Just to confuse the issue!)

Check that you have some supply to at least one side of the switch.(Ignition & control switches 'ON')..(but remembering that this safety "chain" is obviously in series!Follow the colour coded wires from switch to switch) You could even bypass the switches to see if you get the A/C switch to light up....Mmmm?

As I say, it's been a few years, but I hope this information can steer you some way to a solution.

Cheers, Steve.

October 19, 2011

Hi Daragh,
Well, it's been a few years since I worked on Automotive A/C......and certainly not on a 2008 vehicle, so, I may be way off beam here: But here goes!
First stop is to confirm if your system has any gas in ..unfortunately, with your gas (R134a) you will need a set of gauges with special access valves/connectors. These are not cheap.
On older cars, all the power for the A/C system had to come through a series of interlocks...safety switches if you like...these were pressure switches fitted in the low pressure (Suction) & high pressure (Discharge) lines.....they guarded against the obvious "Pressure Too Low" & "Too High" Scenarios....The low pressure switch also guarded against loss of refrigerant, which obviously is not desirable!
But, identify the suction line: It is the bigger diameter of the two. If this switch is 'open'...it may be that you have lost the gas.
On more modern cars it gets more complicated: There are sensors for just about every scenario you can think of! But,I would suggest you continuity check the various pressure switches you can identify in the gas lines.....but remember,one switch in the HIGH/DISCHARGE side will be to turn the condenser fan ON, so will be open under these conditions.....and it may be part of a three way switch.(Just to confuse the issue!)
Check that you have some supply to at least one side of the switch.(Ignition & control switches 'ON')..(but remembering that this safety "chain" is obviously in series!Follow the colour coded wires from switch to switch) You could even bypass the switches to see if you get the A/C switch to light up....Mmmm?
As I say, it's been a few years, but I hope this information can steer you some way to a solution.
Cheers, Steve.

Thanks a million Steve, have no experience of A/C at all (not really a requirement in this climate). I'll try an test it tomorrow evening and post the findings