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...and think about on the Fan Control relay down in front of the radiator. It should have constant 12V from the Battery on both the High and Low speed coils. Both of them just waiting for a ground from 1 of 3 sources:
High Speed...
1) Radiator thermo-switch, 2) Gray pressure switch on condenser
Low Speed...
3) Brown pressure switch on condenser
[the other (purple) switch there is an excessive pressure cut-out in the clutch circuit, so if it's unplugged, there is no way to get 12V from the Low side switch to the clutch.
Since shorting the 2 radiator switch wires* didn't get the fan going, it's good bet there is no voltage to those coils (or thru the HS coil to the rad sw). My son had that problem on his '92 940 and it turned out to be a Gray Fusible Link wire leading from the battery + terminal. I'd say start there.
I was "helping" him by phone, despite which he found the FL (after slitting the outer wire sheath) burned open at the end (about 10" or 12" away). Remember, I never saw this, so I can't describe exactly how that connection is made or was fixed. But he repaired it by cutting the last inch or so off and reattaching the rest of it, which then allowed the fan to run when the radiator switch closed.
BE SURE to disconnect the Negative battery cable before getting into the Positive wiring. I think you'll find 3 or 4 smaller wires at the + terminal besides the big cable to the starter. The Fusible Link will be a thickish gray one.
*"jumping both leads together does not do anything."
THIS confused me:
"I find neither wire going to the temp sensor in the upper right radiator [HAS VOLTAGE?] with the engine off or on." That's what you meant, right?
Otherwise "jumping both leads together does not do anything".doesn't make sense to me.
ALSO: The Fan relay can be unclipped from is mounting and pulled up a bit, if you need to check voltage or operation more closely.
ALSO #2: If your jumping the AC clutch is what's causing the overheat (with no fan), pull the Fan back or out and flush water thru from the front. My son's '92 radiator was really full of crap, and most of the lower fins had perished as they say. Didn't take much to get the Fan on till he put in a new radiator.
"later" 940's may refer to the introduction of factory R134a AC in the '93 940. My son's '92 had been converted to R134a according to underhood labels.
--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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