[V8] A/C electrical circuit

[David Head]

Could be low or high pressure cutout switches bad - they plus a high 
temp cutout also control that relay.

Gunter wrote:

>Anyone know of a way to check if an A/C relay is faulty (other than replacing with another relay)?
>
>My compressor does not come on BUT if I bridge the relay terminals 30 and 87 it does no problem.
>
>There are no error codes when I do a system check on channel 17 on the Head Unit.
>
>I thought that it might be the under-the-dash A/C controller module because I had a front windshield leak that caused water damage in the area............whole relay/fuse box had to be replaced by Keith of Audi Connection due to corrosion...........BUT the A/C controller box and its contents look OK.............
>
>The inside of the A/C relay itself also looks OK...........no signs of corrosion or other problems
>
>
>Again, anyone know of a good way to test the relay to see if it's faulty..............could I run a small current across it to see if it switches on? (how much voltage?)
>
>One thing............the power lead to the relay.........which is #87a............only has 0.06 Volts being supplied to it when the car is running and the A/C system is on (again, the only that does not seem to be turning on is the compressor UNLESS I bridge the circuit...........then it works quite nicely)  I don't know if that's too low to switch the relay.............and if it is too low.............what could be causing it to be too low?
>
>
>Hoping to sort this out..............Spring has finally arrived...............the leather seats will be far too cozy if I don't get the A/C up and running.
>
>Gunter 
>1990 V8 140 000
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