My first post here - G'Day from an Aussie MB owner!

I have a seemingly strange problem with the aircon/climate control system in my 1986 230E (W124) and I can't find any clues in the stickied posts so here is the whole thing any and all suggestions would be very welcome.

I will lay the problem out in steps:

1. The initial problem last December was that the evaporator kept icing up because the climate control was not cycling the compressor but was running it all the time. I tested the temp sensor in the air duct and replaced the climate control box that lives behind the glove box but nothing worked (and the sensor fan is drawing air over the in-car sensor above the windshield) so I had the local AC guy do a dodgy workaround that just cycles the compressor like a non-climate control AC (and that can be reversed if I ever work out what the problem is). I agree that it was not a good solution but at least it gave me AC for the summer.

2. Last week the AC just stopped altogether - it worked one day but not the next. After a bit of stuffing about and asking questions on the Aus MB Clubs forum I removed the cover of the 'Klima' relay and by manually closing the relay contacts the compressor came back to life. I gathered from this and other MB forums that a new relay would probably fix things.

3. The new relay arrived this morning but it makes no difference - the compressor does not kick in with the new relay (but it will with the old relay if I manually close the contact points).

So I have two problems: the first is getting the compressor to run and the second is getting the climate control to work.

With regard to the relay, my only 'diagnosis' to date has been to manually close the contact points in the relay and thus see that the compressor functions - is that really indicative of a fault in the relay? I gather that the relay is the usual first thing to look at and it seems that they do fail on older cars, although there is no sign of heat damage in the old one however the joints where the board connects to the main contact pins has been resoldered at some point in the past.

With regard to the climate control, is it likely that the initial problem with the climate control could have been a result of the relay starting to fail? If that stands a chance of being the case then perhaps fixing the relay might well also fix the climate control (once I pay the AC guy to reverse his 'workaround' handiwork anyway).

From reading various articles I gather that the control unit in the console can suffer from fractured solder joints where the three buttons connect to the circuit boards, and I do notice that the light in the 'EC' button sometimes does not stay on unless I push it again. Could that be the problem? I am quite happy to pull it out and resolder as required. (BTW the climate control panel in Australian cars is a bit different to what you have in the US: I have three buttons vertically up the center of the panel (off/on/demist) and temperature is set by two wheels, one for each side of the car.)

This car has had it's share of electrical gremlins - I sometimes think that perhaps they might all have their source in an aftermarket alarm unit that was fitted when the car was new. It is NOT a tidy installation at all. I disabled it (with the key) a couple of years ago (it used to randomly lock all the doors while I was driving and sound the damn alarm - VERY embarrassing, especially around town!) but I can't help wondering if the messy-looking hack into the MB wiring loom might be doing something funny in an electrical sense.

Thanks in advance!

Roscoe