air con fault '89 300se

[Glenn Smith]

I have just finnished converting a mates 300SE a/c to use R134a, as it had no gas i was hoping it would work once gassed up, but it doesn't, I am getting no voltage to the compressor. Firstly which position should the a/c switch be in (semi auto climate control) for a/c to be on, also getting no or low volts to the refridgerant press. switch, anyone know if I should get a full 12volts here (switch is working) I cannot find a wiring diagram, anyone got one? Anyone had a similar problem or know of a common weakness in this particular model. My thoughts at the moment point me to think its the a/c control unit.

Cheers

 

[Blobcat]

Mercedes run with AC on as standard. If the 'EC' button is illuminated then the AC is off.

 

[Glenn Smith]

Yes am aware of that but this doesn't have a EC button! It has a 3 position rocker switch with an a/c symbol on the lower and another symbol on the upper, red light on each if you push it either way from the middle, below this switch is the recirculation switch. any ideas?

 

[Glenn Smith]

Found the problem, compressor relay/control unit has burnt tracking and a melted resistor, also sussed the switch out it has 3 positions, off is middle, press down for normal and up for constant. attempted repair to relay but i think a transistor has gone as compressor is on all the time now, i guess anew one will make my mate cough, i imagine they are expensive.