A/C Cycles On And Off

[gungfudan]

I have a Mazda B3000 the A/C stays on when it is actually turned on. The issue is when it is off. When off and you select a setting past the MAX A/C setting for instance defrost, floor, etc... the A/C cylces on then off. What could be the issue? Right now I have it unplugged. I would like to figure this out because winter in Mississippi is maybe 20 degrees then 75-80 degrees so having to plug and unplug is a pain.

 

[Dirtman]

There is no problem. It was designed to do that. The AC system is used in ALL settings except forward vent heat. (May still actually come on in this setting as well).

The AC system dries the air to keep your windows from fogging up when the heat is on. Especially in defrost mode.

 

[gungfudan]

Ok weird. I didn’t know that. I would have thought it was messed up. So it is designed to cycle on and off?

 

[Craig0320]

Dirtman is right it is normal. Got to love our weather down here.

 

[gungfudan]

Dirtman is right it is normal. Got to love our weather down here.

Guess I will plug it back in

 

[Dirtman]

I'm not sure how to do it on your generation truck, but on the 98+ models you could add a toggle switch to the solid purple wire behind the controls. This let you disable the AC compressor command so you could run heat or whatever without it coming on. The idea here being to save some fuel. I tried running with the AC compressor off for a few weeks last winter and it made zero difference in fuel consumption, but a tremendous difference on how foggy my windows got. My advice, ignore it and reap the benefits.

 

[Craig0320]

I'm not sure how to do it on your generation truck, but on the 98+ models you could add a toggle switch to the solid purple wire behind the controls. This let you disable the AC compressor command so you could run heat or whatever without it coming on. The idea here being to save some fuel. I tried running with the AC compressor off for a few weeks last winter and it made zero difference in fuel consumption, but a tremendous difference on how foggy my windows got. My advice, ignore it and reap the benefits.

Disconnecting it for a couple weeks told you something about your a/c system also. It means it is working efficiently and the compressor is adding very little drag to your serpentine system. I have disconnected a couple before and gotten 1-1.5 mpg better. You can remove the belt apply voltage to lock the clutch and spin the compressor. Usually the clutch bearing or compressor itself was very rough when spinning.

 

[adsm08]

Ok weird. I didn’t know that. I would have thought it was messed up. So it is designed to cycle on and off?

Yes. By 96 the computer actually have control of the compressor (even earlier on the 4-cyls). It doesn't need much in this mode, it's not trying to use it to cool the air, it's being used as a dehumidifier which takes much less run time, to it should only kick on for a minute, or less, at a time.

 

[Dirtman]

Disconnecting it for a couple weeks told you something about your a/c system also. It means it is working efficiently and the compressor is adding very little drag to your serpentine system. I have disconnected a couple before and gotten 1-1.5 mpg better. You can remove the belt apply voltage to lock the clutch and spin the compressor. Usually the clutch bearing or compressor itself was very rough when spinning.

True but the compressor also simply doesn't run that much in the heat/defrost settings to really make a difference. It's probably running about 75% less in heat/defrost mode than it does in AC mode. When the heat or defrost is running it just cycles on and off enough to keep the evaporator pulling moisture onto it.

 

[Craig0320]

True but the compressor also simply doesn't run that much in the heat/defrost settings to really make a difference. It's probably running about 75% less in heat/defrost mode than it does in AC mode. When the heat or defrost is running it just cycles on and off enough to keep the evaporator pulling moisture onto it.

I agree. I was mainly relating to max and a/c settings. Sorry should have been more specific.

 

[Dirtman]

I agree. I was mainly relating to max and a/c settings. Sorry should have been more specific.

I have always wanted to see how much gas I could save in the summer by not using the actual AC, but the answer would be infinite since without AC my desire to drive anywhere drops to zero.