When does the cooling fan come on?

Surprisingly, I'm having trouble getting an answer to what seems to me
like a simple question. I have a '97 Accord, which is running very
hot. What I've noticed is that if I'm stopped (with the temperate
gauge nearly in the red zone), the fan does NOT come on if the engine
is running. If I turn the engine off, the fan comes on immediately.
If I turn the engine back on, the fan goes off. Is this normnal?

In other words: If the engine is hot enough to require the fan
when the engine is OFF, is it normal that the fan will not come on
when I'm stopped at the engine in ON?

Many thanks.

-Joel Hoffman

 

The fan relay is temperature controlled and will normally come on when
a specific temperature is achieved. The sensor is close to your
t-state flange. you can trace the wiring back from the fan to the
sensor.

Once it comes on it stays on until the sensor drops to the low end of
about a twenty degree F range.

It is possible for the temperature to spike when you stop the engine
becausethe water pump stops circulation immediately. This spike
could cause the fan to come on. However if you are getting close to
the red zone with the motor running it should be coming on before
that.

Air conditioned models have two fans. The one on the battery side is
the radiator fan the other side is the AC condensor fan. Both work
the same way with a temp sensor/relay.

Have you felt the top radiator hose when the temperatur spikes? If it
is not hot then you may have a sticking T-stat that is causing the
spikes.

You could have a bad sensor/relay and it is not turning on the fan at
the right time.

I'm not sure (don't have my manual with my right now) wether the
sensor that turns the fan on is the same sensor that controls what you
see on the gage. If it is it could be bad and you're not actually
getting hot. But if you are you need to get it under control before
you warp a head or blow a gasket.

 

No, the fan is supposed to go on when the engine gets hot. Get this
fixed, because an overheating engine will eventually fail, sticking you
with an expensive repair. I can't stress it enough: fix or get it fixed
soon!

Do both fans come on when you turn the AC on? I suspect they do because
they come on after you've turned the car off.
I think Accords have fan relays, so these are most likely fine if that
is the case.
If you have to drive the car with this condition (fans not running when
they are supposed to), run the car only with the AC on so at least you
are getting proper cooling. You obviously can't run the car forever
like this, but it will get you around town to collect the parts you
need or to a repair shop.

If you're doing it yourself, I'd check the thermoswitch or the
connection to the thermoswitch.
With a multimeter set to volts, you should see approximately 12V across
the switch if the car is cold. When in need of cooling, you will see
zero volt across it.
If you don't see 12V when cold, the wiring to this switch is most
likely the culprit. If you don't see zero volts when in need of
cooling, the switch probably has a bad ground or the switch is bad.
Short the switch to see if the fan comes on. If the fan now turns on,
your switch is bad. If not, report back.

Tegger.com has a section on cooling that might be of use to you.

Remco

 

hold on there cowboy: you've been told to test the sender/relay circuit
how many times? you're getting free advice from people that know what
they're doing. you otoh, don't seem to want to hear it. why are you
bothering to waste your time if you don't want to take the advice you're
not paying for? just pay to get the advice of a garage - if money
changes hands, maybe you'll listen.

 

The cooling fan should come on between 195 and 210F. typically.
Has the a/c harness recall been done to you car? If not I'd get that
taken care of.

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Tp,

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