Radiator fan switch on 98 Chrysler T&C keeps failing

This is a continuation of a previous post a few years ago. I have a 98
Chrysler Town & Country with a 3.8 L engine. The solid state relay that
controls the radiator fans is mounted on the driver side wheel well. I
am replacing this relay for the 4th time and getting tired of spending
$70+ for the darn things.

I have been told that one of the fans may be failing but diagnostics
fail to point out anything abnormal. They will turn on and off just
fine but that is the end of the diagnostics. There is nothing to show
if there really is a fan problem or, if so, which fan. My local
Chrysler service man wants me to "replace both fans" YEA RIGHT!!!. That
still may not be the problem.

One idea in one of the newsgroups suggested that the relay itself may
not be properly grounded. I would think that they would us a closed
circuit and not really need a chassis ground.
Anyone have any thoughts?

Thanks,
J

wrote:
> This is a continuation of a previous post a few years ago. I have a
98
> Chrysler Town & Country with a 3.8 L engine. The solid state relay
that
> controls the radiator fans is mounted on the driver side wheel well.
I
> am replacing this relay for the 4th time and getting tired of
spending
> $70+ for the darn things.
>
> I have been told that one of the fans may be failing but diagnostics
> fail to point out anything abnormal. They will turn on and off just
> fine but that is the end of the diagnostics. There is nothing to show
> if there really is a fan problem or, if so, which fan. My local
> Chrysler service man wants me to "replace both fans" YEA RIGHT!!!.
That
> still may not be the problem.
>
> One idea in one of the newsgroups suggested that the relay itself may
> not be properly grounded. I would think that they would us a closed
> circuit and not really need a chassis ground.
> Anyone have any thoughts?
>
> Thanks,
> J

Well thinking on a regular relay. They have 4 terminals.
Onterminal to usually 12 volt source, and one terminal to load in this
case the fans. Usually the moving switch contacts in the relay connect
this power source to the load. Other 2 terminals are 12v from ignition
to the usually transistor driver that turns on relay (often in
computer).
So for a regular relay often contacts to load have high resistance
from too much current or age. So if fans pull more than they should
part of solid state relay might get burned too. Have someone with a
current probe measure currents to fans and see if one is higher than
the other and with current probe and oscilloscope they can see
commutator damage by shape of waveform.
Or maybe transistor in computer pulling too much current on
signal side of relay. This could also burn up relay. Or maybe one of
the 12v power sources is intermittent causing voltage spikes. Just my
thoughts on the matter.

> wrote in message
ups.com...
> This is a continuation of a previous post a few years ago. I have a 98
> Chrysler Town & Country with a 3.8 L engine. The solid state relay that
> controls the radiator fans is mounted on the driver side wheel well. I
> am replacing this relay for the 4th time and getting tired of spending
> $70+ for the darn things.
>
> I have been told that one of the fans may be failing but diagnostics
> fail to point out anything abnormal.

electric motors that get old or overheat short windings, as a result the
current goes up.

A quick fix is to buy a mechanical lighting relay and run the fan power from
the fan relay to the lighting relay. The lighting relay can take a lot more
power and when it's contacts finally burn up you can just replace it, and
it's
probably a lot cheaper.

If it is a fan failing, do a resistance check of the motors with an
ohmmeter, and
spin the fan gently. If one motor has a lot lower resistance, replace it.

Ted