Jerry wrote:
> Hi,
>
> I have a 91 honda civic with 232,000 miles. Radiator is about 1 year
> old. Recently I noticed the temp gauge running all the way to the red
> then dropping to about half only to repeat the pattern over and over.
> It was almost as if the themostat was working but at a high
> temperature range. Sooo.... I bought a new thermostat and replace it
> (old one didn't look bad at all). No change. There is plenty of
> coolant, no strange noises or leakage, turning on the heat doesn't
> seem to affect the pattern.
>
> For now it seems like it works but just "late". But it has been below
> freezing and it doesn't seem like a good idea to rely on a car that
> has these symptoms.
>
> I noticed the fan is on when I park but have no idea how well it is
> working while driving. Could the fan be coming on late? I find it
> hard to believe that the fan could drop the temperature immediately
> when I'm driving 50mph at 25 degrees.
>
> Any suggestions?
>
> Thanks

I had an '89 Toyota that had the same problem. What I found out is that
there were 3 different temperature sensors/switches that are used to send a
signal to start the fan and one of them was not working (the one that was
used the most by the system).