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Air conditioner compressor

In January, I had the air conditioner compressor replaced in my car. I have always gotten good gas mileage; 36-42mpg. After replacing the AC compressor, I now get 28-30 mpg. Also, the heat does not get nearly as hot. Any ideas?

If the compressor was not working then you would get better fuel economy. After the repair, the engine has to work harder because it’s now pulling a working AC compressor. The blend door may be sticking which will let cool air in with the heat. Does the engine reach operating temperature?

Not knowing the model year of your car, and knowing what kind of fuel economy I get in my 1998 Civic, I think 28-30 MPG in city driving is about normal. I can coax about 36.5 MPG on long highway trips when I closely control my speed, but it isn’t normal.

The compressor running should not drag the fuel mileage down that much.
What year Civic? Just wondering if this car has the compressor located near the distributor and someone removed or rotated the dist. during the repair. If the ignition timing was not rechecked and set properly it could be the engine is running with retarded timing, which will kill mileage pretty quickly.

As to the heat not gettting hot enough, that could be a blend door problem, control panel fault, failing thermostat, or the coolant level is low.

The Civic is a 2002, standard transmission I have been checking the mileage regularly for the 8 years I have owned the car, and always gotten over 35mpg. Now I am loosing an entire 100 miles per tank of gas. So even when the car was new, I got good mileage.

One more thought: you replaced the compressor in January, the coldest month of the year. Cars don’t get as good a mileage in cold weather. The microprocessor enriches the fuel mixture to the engine, and gasoline is blended for easier starts, but as a result doesn’t give the same mileage. See what happens when the weather warms up.

I’d wonder about the thermostat. If the thermostat is stuck open the engine can’t fully warm up, and that would explain both the reduced mileage and the lack of heat.

Is the engine warming up quickly, like it did in the past, or does it take longer now?

Is the AC compressor operating as it should? If it’s running more than necessary that might explain things, too.

It has been a cold winter all over the US, why would one run the A/C when it is so cold? I would check to see if it is running when not needed.

The AC compressor could be running all the time for some reason.
That would cause both symptoms.
When the compressor is off part of the pulley will stand still.
There’s a wire to the compressor you can disconnect to stop it.
If that doesn’t stop it the compressor clutch is defective.

Just a thought…If you leave your defroster on all the time then that might explain some fuel mileage loss. Most vehicles use the AC as a dehumidifier. That means that your AC cyles on and off the entire time the defroster is used.

That’s a real possibility. I said in an earlier post “check to see it the compressor is running when not needed”.

Lowered gas mileage and not as much heat points toward a thermostat that is stuck open.
The car is an '02 so the T-stat is 8 years old. In my opinion, a T-stat is a maintenance item that should be replaced every few years whether it’s bad or not.

Many an engine has been barbecued because of a 5 dollar thermostat sticking in the reverse mode; closed.
All assuming the distributor was not dinked with of course.

I wouldn’t think one would use the A/C in January or Fefruary.

Thanks for all your replies! I found that the switch at the dashboard was not turning off the compressor. Even though I was manually turning the AC off, which comes on when the defrost is on, and the indicator light went off, the compressor was running constantly. The switch was replaced, I have my heat back, and my gas mileage is back to 39mpg on my first tank of gas.

Thanks for the follow-up.