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Need to replace thermo switch and thermostat in 95 Civic



 
 
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  #11  
Old February 16th 05, 12:49 AM
DesignGuy
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I just replaced the thermo switch, and the radiator fan *still* doesn't come
on, even with the AC switched on (the AC compressor fan on driver's side
does come on).

I measured the new thermo switch by putting an ohmmeter across the terminals
and lowering it into a pan of boiling water. After the switch closed I got 1
ohm of resistance. The old thermo switch read 8 ohms. So I guess it was bad?

I'm not sure what else it could be.... shorted one side of the thermo switch
connector to ground does make the fan come on while the engine is running.
There's nothing else in the circuit as far as I know.

The temp guage never rises above 1/3 level (so far). Tegger, you had asked
about the heat output in the passanger compartment. At times, it seems to be
normal. Other times, it seems to be cool, even when the temp setting is over
at max. Could this be due to a bad thermostat or something else?




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  #12  
Old February 16th 05, 03:59 AM
Randolph
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DesignGuy wrote:
>
> I just replaced the thermo switch, and the radiator fan *still* doesn't come
> on, even with the AC switched on (the AC compressor fan on driver's side
> does come on).


I don't believe the rad fan is supposed to come on when you turn on the
A/C. I have seen cars where the rad fan DOES come on with the A/C (e.g.
some model years of the Accord), but I don't think the '95 Civic is one
of them. The '94 wiring diagram does not show a direct connection
between the A/C system and the radiator fan. The only conceivable link
would be that the ECU could turn on the rad fan when using the A/C
(calls for A/C to turn on go through the ECU and the rad fan relay coil
is connected to the ECU in addition to being connected to the thermo
switch). I just checked the behavior of my '94 Civic, turning on the A/C
causes the condenser fan to turn on, but not the radiator fan.

> I measured the new thermo switch by putting an ohmmeter across the terminals
> and lowering it into a pan of boiling water. After the switch closed I got 1
> ohm of resistance. The old thermo switch read 8 ohms. So I guess it was bad?
>
> I'm not sure what else it could be.... shorted one side of the thermo switch
> connector to ground does make the fan come on while the engine is running.
> There's nothing else in the circuit as far as I know.
>
> The temp guage never rises above 1/3 level (so far). Tegger, you had asked
> about the heat output in the passanger compartment. At times, it seems to be
> normal. Other times, it seems to be cool, even when the temp setting is over
> at max. Could this be due to a bad thermostat or something else?


It could be that you don't have a problem at all. This time of year, the
radiator fan on my '94 hardly ever comes on (Northern California, so not
very cold at all). Caroline (who now uses a different name in this NG)
once mentioned that when she did a coolant system bleed, it took a very
long time idling before the rad fan came on on her Honda.

--
================================================== =====
A modest collection of Honda tech info can be found at:
http://www.geocities.com/ng_randolph
  #13  
Old February 16th 05, 09:10 AM
Mike
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In article <PH8Qd.70$tl3.28@attbi_s02>, "DesignGuy"
> wrote:

> I believe I've got a bad thermo switch/sensor in my 1995 Honda Civic LX. The
> radiator fan does not come on when the AC is switched on (though the
> compressor fan works okay).


If you've come to the conclusion of a faulty radiator fan circuit based on
activating the A/C, listen up. The radiator and condenser fan circuits are
isolated from each other. Not all Hondas run both fans simultaneously when
using the A/C system. Your year Civic does *not*. They occasionally
overlap in operation when normal engine fan cooling is needed with the A/C
running. So unless you're having other real issues with the cooling
system, save your money...

--
Mike
95 Civic
  #14  
Old February 16th 05, 04:05 PM
DesignGuy
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"Mike" > wrote in message

et...
> In article <PH8Qd.70$tl3.28@attbi_s02>, "DesignGuy"
> > wrote:
>
> > I believe I've got a bad thermo switch/sensor in my 1995 Honda Civic LX.

The
> > radiator fan does not come on when the AC is switched on (though the
> > compressor fan works okay).

>
> If you've come to the conclusion of a faulty radiator fan circuit based on
> activating the A/C, listen up. The radiator and condenser fan circuits are
> isolated from each other. Not all Hondas run both fans simultaneously when
> using the A/C system. Your year Civic does *not*. They occasionally
> overlap in operation when normal engine fan cooling is needed with the A/C
> running. So unless you're having other real issues with the cooling
> system, save your money...


Actually, I didn't know that. I read otherwise at
http://tegger.com/hondafaq/overheati...ndex/index.htm :
"Start the car and turn on the AC (if so equipped). Both fans (AC radiator
and regular radiator) should turn on.
If the radiator fan is not turning on, the relay, wiring or fan motor is bad
or power is not getting to the fan relay."

Anyway, I did have to replace the radiator since it cracked. The only money
I (possibly) wasted was installing a new thermo switch ($22) and I learned a
little in the process.

Good to know that another '95 Civic owner's fan doesn't come on with the AC
either. I'll just sit tight and monitor the situation before havnig any more
work done.

Thanks everyone for your help!



  #15  
Old February 16th 05, 11:48 PM
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TeGGer=AE wrote:
> "DesignGuy" > wrote in
> news:AiJQd.7373$tl3.1561@attbi_s02:
>
>
> > Actually, I didn't know that. I read otherwise at
> > http://tegger.com/hondafaq/overheati...ndex/index.htm

:
> > "Start the car and turn on the AC (if so equipped). Both fans (AC
> > radiator and regular radiator) should turn on.
> > If the radiator fan is not turning on, the relay, wiring or fan

motor
> > is bad or power is not getting to the fan relay."

>
>
> Hey Remco, is a revision necessary there?
>
>
> --
> TeGGeR=AE
>
> The Unofficial Honda/Acura FAQ
> www.tegger.com/hondafaq/


Tegger, Remco I just checked my 94 Civic(95 engine)
and with cold start with a/c on the a/c fan runs but
the rad fan does not run. It takes more than 15 min
for the engine to warm up enough for the rad fan to
come on. (temperature about 60F) My rad fan starts
at about half scale on temp gage.
Ernie

  #16  
Old February 17th 05, 02:29 AM
DesignGuy
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>
> Just in case it got missed by the OP the first time, I'm reposting what I
> said the other day:
>
> "Personally, I think you're barking up the wrong tree here. 1 ohm or 8

ohms
> means nothing. If the temp gauge never gets past 1/3, the rad fan WILL NOT
> START NO MATTER WHAT.
>
> "If you simulated the heavy stop-and-go traffic like I said for AT LEAST 5
> MINUTES, and the temp gauge DID NOT RISE, then your engine IS NOT HEATING
> UP ENOUGH to make the fan come on.
>
> "I do believe you have a bad thermostat. Replace with new **OEM** for $20,
> then report back, BEFORE you spend bigger bucks on the thermoswitch."


Yep, got it - thanks Tegger.

The thermoswitch was only around $20, I did go ahead and replace it. Based
on what you've said, it was probably good and didn't need replacing.

If I replace the thermostat I'll be sure and get an OEM unit. But I suspect
that the engine is just not getting hot enough. The temp guage goes up to
1/3 shortly after starting up and stays there, never going higher.




 




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