Hi,
Hope I've not missed any relevant posts on this. My problem similar to what I've read. Make and model 1997 Chrysler LHS, 3.5 Liter engine; two fans; two speeds (two relays in module on L.H. side on fender).
Overheats when not at highway speed (stop-and-go or idle). Have confirmed that fans eventually cut-in, but too late to cool engine to proper level. Used to be intermittent, but now pretty consistent.
Have traced as follows:
Replaced relays.
Shorted lo-speed relay primary to ground - both fans run at lo-speed.
Shorted hi-speed relay primary to ground - both fans run at hi-speed.
Traced wire connection from computer module to both relay primaries - both good.
Traced wire connection to engine coolant temp sensor - good.
My chrysler FSM (Factory Service Manual) for this car indicates that Temp Sensor signal controls both temp guage on dash AND cooling fan operation. Since guage shows a rise in engine temp, should also turn on fans I would think (but doesn't). This is why I haven't replaced coolant temp guage.
Dealer just wants to sell me diagnostic time and then talks all the usual BS (flush the system; change the thermostat; etc. etc.) I KNOW the fans are the problem not the cooling system!
Am thinking of wiring toggle switch on dash to short relay return line to ground but that's just my frustration showing. I'm hoping SOMEBODY knows a LOGICAL explanation.
-Hank