A/C has been working great,blower, climate control etc,,, then all of a sudden would not come on.... Fuse is not blown, but on the hot side only getting 2 volts?.... this I have done.

1. You can take a jump hot wire go the other side of fuse, a/c, blower, fan speeds everything works?... wire does get a little hot,, short?......
2.Change out fan reg, on inside fender, both controls behind glove box, $5.00 each, junk yard... stilll doing samething.
3.I had to change the key switch months ago, everything was working fine..
4. Check my gas charge everything fine, again if I jump it a hot wire eveything comes on..cold air... alittle hot in in SC...
5. My Question is there another relay somewhere, is it picking up power from key switch, then to a relay, or straight to the a/c. don't understand the very low 3 volts on the hot side,
6. Even pull the fuse box out and check all the wires on #8 to see if everything is tight...... will listen to any and all input .. luckyme

Does sound like electrical...as opposed to AC...
have you checked your ' pilot operated switch' .. the one/s you adjust on the inside of the car ?
How about the temperature sensor ?
Which AC type do you have...? Can you post pictures of your dash ( wheel selector ?) Inside of the engine compartment... like at the firewall...Do you have that big fiberglass unit under hood ?

__________________
1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/diesel-discussion/10414-help-i-need-check-stretch.html

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

The pilot operated switch works fine.. Don't know where the temperature sensor is located?
As far as what type of ac. not sure what you mean?... wheel selector is on left side of control panel... and all that works when you jump it, with 12v...

All the ac unit is under the pass inside under glove box and center console not really much on fire wall outside... Are you calling the pilot operated switch the climate control knob, red to blue tape on it...

Are you jumpering from the battery to the fuse connector? Or from one side of the fuse to the other?

With the AC on, what does the voltage measure at the fuse box when you have the jumper installed? A 'good' fuse should act much the same. Measure both sides of the fuse to ground, or voltage across the fuse. You should see 0 volts across the fuse (replace the fuse if not - it is bad), and the same voltage (12 to 14 volts) from both sides of the fuse to ground. Also measure the voltage from the fuse box to the positive post of the battery - again 0 volts or at least very close. If you see any significant voltage drop between the battery and the fuse that's one place to look for a loose wire or bad connection. This could still point to the ignition switch, or the ignition switch connector.

If you have a low voltage at the fuse box then either you are drawing a tremendous amount of current (not likely with a fuse in place) or you have a bad connection between the battery and the fuse box. For AC, this is a circuit that is switched by the ignition. Check the connector and the switch. I know you said it was replaced recently, but that's the indication based on your symptoms.

The reason your wire may be getting hot is that you may be drawing current above what the AC is drawing (is the fuse still in place when you do this?) or your wire may be insufficient for the load. I'd need more details to provide a better answer.

__________________
mjk

'84 300SD 119KMi (Liesl der Diesel)
'84 300D 326KMi when the oil left (former parts car)
'82 300SD 253KMi (new parts car)

For #1 - where are you jumping from/to? The battery to the demand side of the fuse?

The supply side (hot side?) is only seeing 2 V?

Per the wiring diagram, fuse 8 gets power directly off the 15x line from the ignition switch via a 2.5 mm red/green wire. I'd recommend tracing the wire back there and making sure the switch is good and the wiring is correct. I think the 15x line only gets power in position II on the ignition.

Maybe you've got a bad connection or a bad internal part of the ignition switch. Is that wire or the switch getting hot? If you're dropping 10v across the switch, that's a lot of power being dissipated there.

I presume you don't have the replacement blower fuse/upgrade. You might want to consider that. It's a matchbox-sized strip fuse outside the fusebox that replaces fuse 8. Fuse 8 has a tendency to melt.

Thanks for all the input will run these test sunday.....

Luckyme