Hello All:

Exactly what does the AC relay do? I am working on faint hope here-- my AC system had a leaky high pressure line repaired and was refilled with r134a last summer. I recently tried to run the AC now that the weather is warming up a bit and I couldn't get the compressor to engage.

It will run if I jumper the low pressure switch, which makes me believe that the system is probably leaky again, although casual inspection shows no oily stains anywhere (I really need to get a set of gauges!).

In any case I am interested in exactly what this relay does...

Thanks!

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Herb Goltz, London, Ontario, Canada '92 245 w/109K mi

>In any case I am interested in exactly what this relay does...

It keeps the compressor from coming on until the engine has been running for a short time - something around 10 seconds.

Even when they were new, these systems were never good about holding a charge for long periods of time - especially if the A/C isn't used often. Your best bet is to put dye in the system, jumper the low pressure switch, and look for your leaks. Good news is that the price of r134a is now starting to come in line with what Freon used to cost in the '80s, a couple of bucks per pound.

The A/C relay just fires up the blower motor (if it isn't already on) when you turn on the A/C.

Simply that, when the compressor is engaged with the switch, the fan is forced to run.
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'73 142, '75 242, '75 245, '80 245, '86 244, '87 745T