Air Con Wiring Queries

[bobster]

Does anyone have a wiring diagram that shows how the two Air Con relays should be wired above the passenger footwell. Or the configuration of wires on the rear of the dash control module.

I've had a mobile technician round to see why the A/C's not working and apart from not having a full charge of gas he thinks the relays are wired wrong and can't think how it ever worked. I assume it must have once!
Result is he's gone away to look for wiring diagrams and has left the relays and wires disconnected for the moment. He's tried all combinations trying to make sense of it, but there doesn't seem to be a switched feed to energise the relays. Also one of the relays seemed to be getting a live feed to both sides?
By bridging contacts we have proved the compressor swiches in and the condensor fan runs.

The sytem is a Diavia which was fitted in 97 with I think a 993 dash control unit.
There is also a mod that appears to have been made to the connector on the back of the control module where an additional (green) wire has been added to one end of the connector and evidence of one which has been removed leaving the terminal behind as evidence.

I realise I've not been very clear, but does anyone have any A/C info they think might help please?

Bob.

 

[Paul 944 s2]

Ebay item 350064648586 has the wiring diagrams and lots of other info just £2.99 inc postage

 

[mr pg]

I came across a series of pdf files on the web recently covering bodywork, engine, etc. Volume 7 covers electric wiring diagrams. The files are too big to post here, but you could try a search. I'll have a look to see if I can find the web page again.

 

[bobster]

Thanks for the reply, I bought the CD which arrived today.

Unfortunately I wasn't really able to use the wiring diagram, due I think to the system being after market fitted and colours and routing seemed to differ.
However we eventually found the fault which was the main fuse, which although testing OK through the holder had corroded at one end. So its now been replaced with a modern blade type fuse and holder.

This should have been the fix. But unfortunately after pressure testing and regassing the system it now runs as soon as the ignition is switched on. The only way to turn the A/C off is by pulling the fuse.

It seems to work well but the dash control has no effect switching on, or off, from the buttons. The lights come on and go off on the switches, but it's being over ridden somehow.

Can these units fail open circuit? Has anyone come across this before? Any ideas?

Not sure what to do now, so need some help please.

Bob.

 

[Tony M]

My suggestion would be to try the logical approach if you have no diagram, and is based on your car being positive earth.

One relay is to switch the compressor clutch and the other the condenser fan.

With all wiring disconnected find which wire provides the initial 12 volt negative supply when the A/C switch is operated. Once you have done this connect it to one side of one of the relay coils.Then find a 'positive' wire and join it to the other side of the coil of the relay and loop it on to the other side of the other relay.

Locate the condenser fan pressure switch and find which wire sends a negative signal to the relay. You may have to do this by colour code as the A/C will have enough pressure at this stage to operate the pressure switch. once you have determined which one it is ,stick it onto the remaining coil connection.

By a bit of ingenuity you should then be able to sort out the switching circuit for the compressor clutch and the Condenser fans. once you have sorted these out connect the compressor circuit to a normally open contact on the relay from the A/C switch circuit and the condenser fan circuit to the 'other' relay.

In the past, I have identified circuits by having a length of wire connected via a fuse (ocassionally !) to the battery and if one 'Dabs' the end on various wires in question, the likeleyhood is that sooner or later you will find the condenser fan runs or the compressor clutch 'Clacks' in. You need to be firy brave to try this dodgy method but it often works !

Disclaimer : If you Fry your wiring in the process, it is nothing to do wth me and you are not allowed to use physical violence against my person.[]

Good luck.

 

[Alexander_Drobik]

I don't know if you tried but I would suggest finding someone who still installs Daivia eg readerair - and have them check it out. The very low fuse type check to see if anything gets live may point you in the right direction but it may not be the best solution. Just needs one customised extra line somewhere and you could short something - at least if someone else does it they have to fix ;-)