Conference vmsnet::car$note:carbuffs

	1991 Chrysler Fifth Avenue, 3.3l Auto, AC, 55k miles. The car
overheats when "stuck-in-traffic" and cools back down (albeit slowly) at
speed. It has 2 electric cooling fans which don't seem to operate no
matter how hot the car gets. Fuse for the fans is OK. What's next? Sensor
in the radiator somewhere? A relay under the hood somewhere?

thanks,

Rick

re .60 overheats in traffic:

follow the wires from the fans.
i do not know that car, but there is typically a thermostat as a switch.
when it gets hot, it closes the circuit and the fan runs.
the thermostat is probably near the bottom of the radiator, looking like
a screw in plug with two electric terminals on it.
perhaps the wire fell off, or the contact is dirty, or broken off.

the fan probably works.  bypass the thermostat to verify it.

it is easy to replace the thermostat, but you might want to delay
that until the next radiator flush or antifreeze change.

the thermostat for the fan is not the thermostat that controls water flow
in your cooling system.

you can bypass the thermostat and control the fan with a switch you install.

the fan not turning is a fuel economy measure.  you could connect the two
wires at the thermostat, and let the fan run all the time.
it probably will be all the time.  the circuit is typically not
controlled by the ignition switch.  so if you want it to always run but
only while the car is on, you will have to move the whole circuit to 
a different point on the ignition switch.

i did the manual switch bit when it took months to get a replacement
thermostat for a fiat.

    I had a simular problem with a Pair O'Cavaliers, there is a pickup near
    the actual thermostat housing on the engine, and a relay on the fender.
    
    Appears that the sensor closes making the relay close, and then the 
    fan turns on.  On both Chevys it did not work, replaced both items, and 
    still the same.  Could be a build up of crud under the sensor, I did 
    not measure the sensor, just hot wired the fan, and had a jumper to 
    run the fan.
    
    Dave

    Can you get a wiring diagram for it?
    
    Do either of the fans run if you turn on the AC? (ambient will have to
    be above about 40F for this to be a valid test).
    
    There is undoubtedly a relay, but I'm not familiar enough with that
    vehicle to know which particular system you're up against.. I suppose
    the first step would be a voltage check at the fan connector(s) when
    you think the fans should be running, and a continuity test of the fan
    motors..
    
    The temperature sensor for the fan could be airlocked (air in
    coolant)..
    
    The relay contacts or the connectors to the relay could be
    dirty/corroded (this has happened on our '89 voyager).. I'd bet in '91
    the relays were still the metal-cased jobs mounted in the engine
    compartment (rather then the plastic-cased ones all inside a box); look
    at the colors of the wires on the harness side of the fan connectors
    and try to match them up to the relay connectors..)
    
    The fan motor(s) could be bad (unlikely that both would be bad, unless
    one has been bad for a while.. the voyager has two fans, but one is for
    cooling only and the other is for AC only.. both eventually needed
    replacement) (they are not cheap)
    
    ...tom