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Discussion Starter #1
So I have a 1998 crv and the cooling fans work but dont come on when the engine gets hot enough. When I turn on the ac they both turn on.

Here is what I have done

Checked fuse: seems fine

Checked fan wiring and connections: everything seems to be in good shape and like I said they work good

Checked and replaced radiator fan coolant switch: still does nothing when at the proper temperature.

Checked wiring going to the switch: I pulled the connector and put a safety pin in it connecting the circuit. When I do this and turn the car on the fan comes on immediately, again showing that the fans work just fine.

I'm getting a little fustrated because I thought the switch was the problem. But when I replaced it and heated the engine slightly past operating temperature nothing happened.

Any clue what else it could be?
Many thanks!
 

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I think there are 2 separate temp sensors. I think the second one might be by the thermostat and vaguely remember someone else with a similar issue a few years back and that was his solution. Not for certain though. Also, check the fluid level which I would assume was done at least when the switch was replaced.
 

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As @Shryp mentions above, a low coolant level could cause a fan not to turn on--where the sensor is located, low fluid could leave a pocket of air there in its place, so the sensor can't read the coolant temperature. This sensor is different from the sensor which shows the coolant temp on your dashboard.

The 1st gen CR-V does not have a bleeder for the coolant, but I think there is a way to "burp" the air out of the system, if it doesn't work itself out. Try that first before troubleshooting further.
 

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There are actually 3 I think. The one in the thermostat housing is the fan switch. So make sure you swapped the correct sensor, and make sure your cooling system is full and purged. If the above is correct, then I would get a scan tool and check the temperature that way and make sure it is getting hot enough to turn the fans on. The gauge isn't exact and these switches don't close until around 200 degrees or a little better. Would suck to bounce around looking for a problem that isn't there.
 

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Discussion Starter #6
There are actually 3 I think. The one in the thermostat housing is the fan switch. So make sure you swapped the correct sensor, and make sure your cooling system is full and purged. If the above is correct, then I would get a scan tool and check the temperature that way and make sure it is getting hot enough to turn the fans on. The gauge isn't exact and these switches don't close until around 200 degrees or a little better. Would suck to bounce around looking for a problem that isn't there.
So I need the coolant to be completely full to work? After replacing the switch I only added in a little bit because I wanted to make sure it worked first. I thought the switch would get hot enough from the parts around it as well as the little coolant added in. Maybe this is my problem??
 

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Discussion Starter #7
As @Shryp mentions above, a low coolant level could cause a fan not to turn on--where the sensor is located, low fluid could leave a pocket of air there in its place, so the sensor can't read the coolant temperature. This sensor is different from the sensor which shows the coolant temp on your dashboard.

The 1st gen CR-V does not have a bleeder for the coolant, but I think there is a way to "burp" the air out of the system, if it doesn't work itself out. Try that first before troubleshooting further.
So I need the coolant to be completely full to work? After replacing the switch I only added in a little bit because I wanted to make sure it worked first. I thought the switch would get hot enough from the parts around it as well as the little coolant added in. Maybe this is my problem??
 

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This is the "official" way to top it off, per the service manual. (Part of a longer procedure.)

9. Pour coolant into the radiator up to the base of the filler neck. When pouring engine coolant, do not let coolant spill on any electrical parts or the paint. lf any coolant spills, rinse it off immediately.

10. Start the engine, and let it run until it warms up (the radiator fan comes on at least twice).

11. Turn off the engine. Check the level in the radiator, add coolant if needed.

12. Put the radiator cap on tightly. then run the engine again and check for leaks.
 

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Yes, it needs to be full. Air doesn't transfer heat like liquid. If there is air in the thermostat housing and coolant isn't covering the switch, it wont get hot enough to close. Fill it up and purge the air. Then if it doesn't work, continue troubleshooting.
 
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