94 Civic A/C stops cooling...


Old 04-02-05, 01:27 PM
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94 Civic A/C stops cooling...

I've got a 1994 Honda Civic 4-door LX with A/C. The A/C system is R-134. Over the past year or so the preformace of the A/C unit has been degrading.


- A/C works great, nice and cold, in cool weather or in hot weather for a little while. After sometime (less time when it is hot outside or the vehicle is in stop and go) the A/C starts blowing warm to hot.

- When the A/C stops cooling and the engine is at idle the RPMs will rev up about 500 off and on about once every two seconds. (So basically the tach oscillates between ~700 and ~1200 rpms).

- Definately appears thermally related. When on the highway such that there is lots and lots of airflow in the engine compartment it is seldom a problem. In colder weather it is seldom a problem. In hot weather idling at a stop it gets unhappy fast.

- If you turn the A/C off and do some highway driving and turn it back on again it's happy again. Slow down or stop for awhile and it'll go kaput again.


- A/C unit was serviced about 6 years ago - condenser had a leak. Condenser was replaced and system recharged.
- Problem free otherwise.
- I live in hot places (Mojave desert last year was where it started, now in Sonoran desert and it's starting to get hot!).

Troubleshooting so far:

- Checked the obvious thermal issue that the condenser fan might be broken. Nope, it seems to work just fine - turns itself on and off as it should. The fan is electric.

- I'm guessing the RPM hit is from the compressor, but that's just a guess. It seems to be the only thing that could put a load on the engine. Why it stops and starts like that I don't know.

Anyone got any bright ideas?

Thanks a bunch in advance,

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Old 04-03-05, 09:47 AM
Lugnut's Avatar
Join Date: Jan 2001
Location: Kansas City, Missouri.
Posts: 1,172
Frequently compressor cycling is one symptom of a low charge. Given that leaks are more common as time goes on, I would begin with simply getting the pressure readings with a set of guages. That would confirm a low charge, and would likewise indicate other conditions that may be present.

If you can see the evaporator line as it leaves the evaporator, it should feel cold to the touch and might even be sweating. If it is not cold, that is another indicator of a low charge.

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