Thread: Air con wiring advice needed?

Oh, one more thing mate. The more I think about it and may be wishful thinking but the air con guy reckons it was definitely coming on and off when he was pulling at the wiring at the fuse box. That would lead me to suspect the wiring off the three speed switch as its in that proximity.

To get at the switch is it just a matter of undoing the four screws at the top of the underdash unit and dropping it down a bit to get at it?

from memory the switch plate that its mounted in is only a pressin fit or secured by a handfull of screws.

undo those and it should pop out... Last one I did I fixed by pulling out one of the vents and probing at it from inside the ducting.

merry Xmast to you too mate, and if you cant get it sorted before mid JAN drop me a hoy when I get back and we'll ine out sorting it over some coldies.

In a very rough sense, regard the negative side of the battery as the Neutral/Earth in AC and the Positive side of the battery as the Active in AC. The only difference is that DC is always traveling in one direction as opposed to AC which travels in both directions alternately. Any metal part of the car can be regarded as Earth, In most instances any Black wire can be regarded as Neutral and any Brown wire is a direct feed from the Positive side of the battery, Regard this as Active.

There is a standard for British cars wiring loom colours and I shall attach the PDF in this post.

This will allow you to get a feel for what does what in your wiring loom. It is not necessarily 100% as your vehicle may have had mods done to it by previous owners.

Any original wiring will be in a taped loom so that should make it a little easier to decipher.

Colour_code_for_vehicle_wiring_-_new_order_2.pdf

not quite, you regard DC negative as the earth From AC and you are going to come acropper..

assuming a "negative earth" vehicle configuration. (negative terminal connected to chassis/body)

assume that the negative is neutral and positive is active.

Hello. Spent a couple of hours fiddling with the air con today and nothing was as it should be on the wiring diagram I have. Wiring colors on the back of the three speed switch were all different. Any way, persevered and fiddle around and I think I found what I thought was the pressure switch at the front of the vehicle behind the radiator grill. I was assuming the little radiator at the right side of the engine radiator was the condensor, although that is the inter cooler eh?

Anyway, I bridged the pressure switch and that's definitely the problem, all working fine now. I'm nearly 100% it's just faulty too because it was cutting the air con out even on a cold start (so not due to icing up), and then come back on, then off, then on again. I imagine if the evaporator was icing up I would end up with a puddle of water on the passenger side floor?

I've left the bridge in for now because I want to take it for a decent drive and make sure all is ok. I'll keep the thermo turned right down. Can I do any damage or is it likely to be ok? Will be taking it to have it replaced tomorrow if I can find a fridgy open. I assume I need an air con guy, not an auto elec?

The last two photos are of the pressure switch and the two wires going into it.

My next question is where would the condenser radiator be and should it have an electric fan? Unless it's in behind the radiator shroud and I can't see it from from the grill? (please forgive my ignorance if I'm way off course :-()

warning lights are on......

somethings not jelling with what I remember about the deefer AC

Dont waste your money on anything Ive got to have a think about it... it sounds like its gassed wrong.

Didn't bloody fix it as it turned out. 10 mins down the road and did the same thing. On for ten minutes, off for 10 minutes.

One thing I did notice today was that the 3spd switch at the back was getting warm near the black wire terminal.

Sounds suspiciously like a loose/hot running terminal somewhere. Clean and tighten any terminal you can find. Install a relay so the compressor clutch doesn't load up the circuit, ie use the compressor wire to switch a relay that takes its power from the battery or other major battery circuit. I have done this mod on a number of older style a/c's which have the compressor switched by the thermostat directly. Quick to do.