Thread: 89 classic air con

My 92 aircon fan switch has become temperamental and sometimes does not switch over to the aircon fan ( and presumably compressor) unless I vigorously move it to and fro a few times and it particularly does not like position 1.

There was a write up a few years ago on pulling the switch out and cleaning it up, which I guess I will do "one of these days"

I suggest this as a place to start.
Regards Philip A

Your heater slide for hot/cold is also the thermostat adjustment for aircon temp.
There is 2 wires going to this if you short them together this will tell you if the thermostat is working. It is possible that the wires have fallen off, therfore no connection.
the other thing u can do is slowly push the heater slide towards the red (heating side) and listen to see if u can hear the thermostat click at around the halfway pos. Thats of course its not red hot in the car as then it should be on no matter where the slide pos is.
The thermostat capillary tube is inserted in the bowels of the aircon evaporator and when hot the liquid in the tube expands pushing a set of contacts in the thermostate which trigger a relay or switch to turn on the compressor.
to access the thermostat u need to take of the knobs of the heater slide control and undo the 2 screws then have a look behind the switch and you will see the thermostate and the wires on the bottom.
There are 2 screws that also take out the switch assy..from here it gets fiddley
Brad

Good tips guys I will make a start with the thermostat controller dissasembly .

Originally Posted by Bradtot

Your heater slide for hot/cold is also the thermostat adjustment for aircon temp.
There is 2 wires going to this if you short them together this will tell you if the thermostat is working. It is possible that the wires have fallen off, therfore no connection.
the other thing u can do is slowly push the heater slide towards the red (heating side) and listen to see if u can hear the thermostat click at around the halfway pos. Thats of course its not red hot in the car as then it should be on no matter where the slide pos is.
The thermostat capillary tube is inserted in the bowels of the aircon evaporator and when hot the liquid in the tube expands pushing a set of contacts in the thermostate which trigger a relay or switch to turn on the compressor.
to access the thermostat u need to take of the knobs of the heater slide control and undo the 2 screws then have a look behind the switch and you will see the thermostate and the wires on the bottom.
There are 2 screws that also take out the switch assy..from here it gets fiddley
Brad

Nailed it Brad . I just bridged the wires to the thermostat controller and the aircon fired up .
Does this mean I need to buy the thermostat ? Ive got it free but the capilliary tube is stopping removal . Can you direct me to the other end you say is in the evaporator ?
Cheers for your help again guys

Hmmmmm
The tube goes up and over to the left hand side of the dash and then into the eveaporator where its wedged in between the fins. To get to it you are best removing the front dash where the vents are. Or get a new one and cut the other out the way and feed the tube back into the fins.
If you can get the actual thermostat out there are 2 very small screws underneath it that are for cut in and cut out contacts.In other words they are a fine adjustment for the slide to turn on or off the contacts inside.
Maybe you can spray some wd 40 inside the thermostat as its possible that the contacts are contacting but not actually making a circuit. This is a common problem with these sorts of switch contacts, they tarnish from lack of use.
I would spray first as all the rest of the above is time consuming
Brad

Brad thats a great help I have the thermostat just out through the dash and can easily access it . I will try your suggestion .
Do you mean remove the 2 small screws and squirt wd40 or electrical contact clean or something in through these screw holes . If i remove the screws will any bits fall out ?
Cheers Mark

NO dont remove them they are a small adjustment screw only..i.e if the main slider was all the way the the left...maximum cold and you adjusted the correct screw then you would make it as if the slide went a bit further electrically but not physically by adjusting the small screw increasing the time the compressor stayed on= more cold
..The same applies if you were at the other end with the slide it would decrease the off time..I hope you get my drift
When you spray it work the slide back and forward
have you heard THE THERMOSTAT click when u move the slide across and back?
That is very important as it tells me that the contacts are trying to work. If you hear no noise at all then the its possible that the capillary tube that works the contacts may have been broken or has leaked.then you will need to buy a new one
Brad

It does click .
With it disconnected and a multimeter connected across the 2 terminals it is open circuit all the way throughout the slide motion