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Old 08-22-2007, 06:28 PM
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rjk rjk is offline
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Join Date: Oct 2002
Location: Atlanta metro area
Posts: 199
Thanks for the info.

T-stat is a month old (replaced when a "mechanic" told the wife that was her problem).
Radiator is less than 2 yrs old.
Pressure cap is good & system holds pressure (I have a Stant pressure tester).
A-Frz is new & properly mixed (done when t-stat was replaced, I checked it w/hydrometer)).
So that leaves the fan coupling...hmmm.

No bubbles in freon & air coming through vent is cold even w/blower not engaging. Nice and cold when it does engage.

I'm not sure which sensor is for which but correct me if I am wrong here.

The sensor in the T-stat housing with 3 terminals is for the dash gauge?
No continuity between any terminals nor between any terminal & ground.

The sensor sitting vertically in the water passage of the intake manifold w/2 terminals (front-drv side of engine under the air filter) is for the electric fan?
If so then the resistance of the sensor is 2.51k @ 90-95F ambient air temp. Tested it when I got home after a long hot day in the driveway, coolant must be at least that temp.
Resistance too high?

Where is the fan relay?

I see mention of an A/C lock out sensor in the parts section, is it what I think it is? Cuts off the A/C when the engine temp is too high? Or am I thinking too much?
I also see an Aux Fan Switch (1 terminal) mentioned that looks like the sensor mounted next to the 3 terminal sensor in the t-stat housing (it also looks like the A/C lock out switch). No continuity here either between terminal & gnd at 90-95F ambient air temp.


1999 E320 (gave to daughter) 250K
1994 F150 (may be the end of its road) 240K
1989 560 SL (Reassembly after paint job) 160K
1986 560 SL (deceased., gave it's life protecting my wife)
1988 300 TE (departed)
1994 945T (still running strong with an upgraded cam) 349K
1986 242Ti (deceased)
1968 GT500KR (under restoration)

Last edited by rjk; 08-22-2007 at 08:02 PM.
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