Radiator fan switch test and replace - Honda-Tech - Honda Forum Discussion


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Radiator fan switch test and replace

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Old 10-12-2005, 11:07 AM   #1
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Default Radiator fan switch test and replace

This is about the radiator fan switch located right beside the thermostat ('99 4-cyl). I think mine's not working because the fans dont come on when the engine gets hot, which they used to before. I unplugged the connector on the switch and shorted the contacts, the fans came on so nothing else in the circuit is wrong.

I believe the temperature rating for the switch is 196-203F.
Are there any aftermarket switches that close (switch on) at a lower temperature
like 170 or 160F ?
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Old 10-12-2005, 11:40 AM   #2
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Default Re: Radiator fan switch test and replace (AnAccordIsForever)

Use honda factory switch. I have a 98 lx 4-cly with 140k and still original switch working perfectly. Why has your gone bad?
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Old 10-12-2005, 11:45 AM   #3
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Default Re: Radiator fan switch test and replace (Elvis1977)

I have no clue why it would go bad, out of all the things that could go bad by 77k miles. I tried checking resistance also, cold is open but engine hot still doesnt show some resistance.

After how long the engine has been running typically does the coolant temp reach 190-200F ? I remember only once when I left it idle for a while (>5mins), the fans kicked in but went off in a matter of 3 or 4 seconds.
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Old 10-12-2005, 11:51 AM   #4
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Default Re: Radiator fan switch test and replace (AnAccordIsForever)

On a hot day, they will kick on about 10 minutes of idling. On a cold day, probably longer. What does the temperature gauge say? Does the needle point in the red?
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Old 10-12-2005, 12:14 PM   #5
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Default Re: Radiator fan switch test and replace (Elvis1977)

Temp gauge is showing fine - a little under halfway mark between C and H - which leads me to believe that the thermostat is working fine and the coolant is flowing as it should.
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Old 10-12-2005, 12:19 PM   #6
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Default Re: Radiator fan switch test and replace (AnAccordIsForever)

The switch is probably ok also. Nothing to worry about.
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Old 10-12-2005, 12:20 PM   #7
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Default Re: Radiator fan switch test and replace (AnAccordIsForever)

That isn't supposed to switch the fan on until the temperature gets hotter. Usually a little above 1/2 on the gauge.

It's just an SPST switch. It's supposed to measure open circuit until it switches ON. It's not a variable-resistance type of sensor. You can test it by putting it in a pot of water with a thermometer.

This time of year (in MN) you'll probably have a hard time getting your engine hot enough to switch it on.
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