Cooling fans not running - overheating - Drive Accord Honda Forums |
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post #1 of 7 Old 04-20-2007, 05:46 PM Thread Starter
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Cooling fans not running - overheating

I have an '04 Accord 4 cly. with 71k miles. Other than a rear brake job, I haven't had to do anything but routine maintenance. Coming home from work the other day I saw that the temp gauge was just below H. I pulled over at a gas station and checked my coolant reservoir. It was just a tiny bit above the low line. I bought some antifreeze anyway and topped it off. The rest of the drive home I constantly monitored the gauge. I had the heater on full blast with the windows down (it was about 70 outside). There was plenty of heat coming from the heater. The gauge drifted up and down the entire ride home and didn't seem to matter whether I was at a stoplight or driving 60 mph. It fluctuated mainly between normal (just below the halfway point on the gauge) and about 75%. Occasionaly it crept higher and the needle would move quite a bit at times and then hover before creeping again.

When I got to where I was going, I kept the car idleing and checked under the hood. Neither of the two fans up front were running. After getting home, I checked again (with the needle above normal) and still not working. I never hit the red line though. The reservoir level is exactly where I filled it yesterday, so no leaks. I checked the cooling fan fuse and it is okay. What else can I look for? I'm thinking of bringing in to the dealer tomorrow since I will have a ride although I would of course prefer trying a few things myself. Any ideas would be greatly appreciated.

2004 Accord LX Sedan, I4 A/T
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post #2 of 7 Old 04-20-2007, 05:49 PM

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Still under warranty? Then dealer it goes to. That's not something you should even have to mess with yourself. There's something really wrong obviously. If you're loosing coolant, could your radiator have a leak possibly as well? Or does coolant burn away??? Not a mechnaic so not really sure on that.

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post #3 of 7 Old 04-20-2007, 05:54 PM
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An obvious thing to check would be the temperature sensor for the fans. I don't know a whole lot about the electrical system of the newer Accords, but if you've got a good fuse but no spin on the fan you've got a problem somewhere between the sensor and the fan's wiring.

Though I guess the fans could be bad... it'd be weird for both of them to go dead at the same time - have you noticed both of them running previously or just one? It's a long-shot that this would be the problem, though. My money would be on the sensor.
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post #4 of 7 Old 04-20-2007, 06:32 PM's Avatar

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Pull the plug of the radiator sensor and short across its pins, if the fans come on, then it's the sensor failed.. If the fans don't come on, get the dealer to sort it for you..

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post #5 of 7 Old 04-20-2007, 07:24 PM

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On the '04s there is no radiator sensor, the ect sensor that the computer (pcm) reads controls the fans. The pcm will ground the fan relay(s) when the temp is reached.
On gen 6s there is a fan control switch on the thermostat housing on the outlet side on 4 cylinders.

If it was getting hot while driving, the fans won't help, the airflow from driving at speed is more than enough.

The thermostat could be stuck closed, running with the heater on full is usually more than enough to control engine heat under idle and low load operation.

You could try swapping the cooling fan relay(s) with others that are the same in the fuse box. I'd try switching with a non-critical one, say the a/c clutch or the blower relay if they are the same. I haven't looked at the manual to know, though.

You're going to want to dump out the coolant reserve tank of the non-Honda antifreeze, conventional green coolant isn't chemically compatible with the extended life antifreeze Honda uses.

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post #6 of 7 Old 04-20-2007, 09:20 PM
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maybe this can help chase down the problem:
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File Type: pdf 04 fans troubleshooting.pdf (33.5 KB, 3440 views)
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post #7 of 7 Old 04-24-2007, 07:33 PM Thread Starter
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Exclamation Update

Thanks for the troubleshooting guide Princess. I tried a few things but then brought it in to the dealership (not under warranty). I was told the heater control valve assembly had to be replaced. When I pick it up tomorrow I plan on discussing this in more detail. He said this unit is what controls your cabin air temp depending on whether you have the controls on hot or cold. I would think that this would then affect the HVAC system in regards to air temperature coming through the vents, not the engine overheating.

For archival purposes, I will post again based on what I learn tomorrow. For what it's worth, this valve assembly, thermostat (recommended to change by the mechanic) and coolant swap cost $342.

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