2002 Honda Civic Heater Acting Up

TCT06412

MEMBER
2002 HONDA CIVIC
4 CYL
FWD
MANUAL
185,000 MILES

I have a 2002 Honda Civic EX. The heater is slow to put out heat, even when engine is warm.

On the highway the heat works great at speed. If I slow down or go into city traffic and do stop and goes and revs go down to say 1000 rpm it starts putting out cold air again.

Sometimes when I slow down the heater doesn't heat but the temperature gauge climbs rapidly to near the red line for a few seconds and then drops rapidly back to normal.

Mechanic has replaced thermostat (twice), coolant, flushed system etc. Still the same problem.

Any advise is appreciated.

8 Replies

LEGITIMATE007

MECHANIC
5,121 POSTS

I suggest one of two things is mostlikely the problem, the engine coolant temp sensor may be faulty and giving false signals and the water pump itself, is not pushing the coolant into the heater core as it should, causing the fluctuation, but, I just thought of a possible, partially clogged heater core. A pressure test of the coolant system should verify if the the core is clogged. Or even if the radiator is clogged for that matter.

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Tuesday, March 23rd, 2010 AT 7:04 PM

LEGITIMATE007

MECHANIC
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A coolant system pressure check will help narrow down and determine if the water pump is faulty

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Tuesday, March 23rd, 2010 AT 9:43 PM

TCT06412

MEMBER
5 POSTS

Finally replaced the water pump (and timing belt) and will wait for the winter to check the heater. However I notice also a problem with the A/C. It works fine, most of the time, but will stop sending cooling air for a while and then start up again.

Is this the temperature sensor? Is this a mechanical sensor on a 2002 Civic EX (at the back top of the engine) or is it an electronic sensor.

Thanks

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Thursday, August 12th, 2010 AT 8:44 PM

LEGITIMATE007

MECHANIC
5,121 POSTS

As far as the a/c. Can be a couple of things doing that. One would be the ambient air temp sensor, (only came on some honda civics. And the expansion valve. I would just bring it to one of those places that "will check your a/c system for free" and have them tell you exactly which one it is. Then you can turn around and replace it your self if possible. And the ect/engine coolant temp sensor is electronic(thermistor). Is a very simple design, basically just a thermometer inside a little housing that creates a certain amount of voltage according to how hot the coolant is.

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Friday, August 13th, 2010 AT 6:54 AM