OK, after looking at the diagrams, I find a reference to the safety switch Steve talked about (pin 49 at the 5 pin changeover), however, I find no switch. This 5 pin replay is the relay that was clicking yesterday.
Today, I disconnected the single wire from the temp switch as well as both leads coming off the A/C switch. Upon grounding the single lead to the block, the fan kicked on and remained running after ungrounding it. I had to turn the key off to stop the fan.
Next I jumped the two leads that attached to the A/C switch, again the fan ran. Again, I had to turn the key off to stop the fan.
With both switches disconnected I started the engine, kicked on the A/C and attached an ohm meter to the A/C switch leads and the single post of the temp switch. At approximately 195dF the A/C switch made contact. The 212 temp switch did not make contact until the gauge was nearing the red.
Can a bad 212 switch affect operation of the A/C temp switch and keep the fan from coming on, or are they independant?
Last thing I checked was continuity of the leads going to the fan from the A/C switch. With the meter set to 200K and one lead to each wire I showed 0.6 when I expected full resistance (0.0). Checking the wires individually to ground, one wire reads 0.0 the other reads 0.6 (I don't remember which was which).
Does this sound right or does it sound like the fan motor has started south?
With the daily temps hitting the low 100's, I really need to get this sorted out quickly.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.