Idle Irratic When Heater Is On

J

JERM

Registered
When I turn the heater on in my 93, the idle goes up and down randomly. When the heater is not on, it idles normally. I figure it might be wiring but I am not sure. Any suggestions on what to check for?
 
its because the clutch is engaging on your ac compressor when you have heat or ac on. when the compressor kicks on in any car the idle will go up.
 
So its normal for the idle to go up and down constantly? The idle goes up and down a few times within a 5 min period. Heres an example: I start the car to warm it up in the morning and i turn the heater on 90 degrees. While it is warming up and still blowing cold air out the vents the idle will go up and down about twice a min. I thought it cycle once the inside temp is up to 90 degrees and then the compressor turn off until the temp drops inside the cab again, to maintain that temp. Hope that makes since.
 
its probably because the compressor is cycling the clutch never stays engaged all the time, it cycles, when it does, it will cause the idle to go, soon as it disengages the idle will drop.
 
You may be low on refrigerant.

I wish it wouldn't cycle the compressor, but it's all part of the system.

I don't think it does it when the EATC is set to "VENT"
 
The A/C shouldn't turn on in the "heat" function when its blowing on the floor, right?
 
Well i glad this is normal and not another think i have to fix, lol
Thanks for the help guys!
 
J said:
The A/C shouldn't turn on in the "heat" function when its blowing on the floor, right?
Click to expand...

It's been said here before that the only time the compressor does not run is when it's on vent. Not sure, but I think that came from Driller.
 
From the manual...

Automatic

Pushing any button, except OFF, will put the system in automatic operation. The WARM and COOL buttons allow the user to change the set temperature. The A/C compressor is automatically engaged in all function positions except OFF, VENT and FLOOR. The discharge air temperature and blower speed are automatically set to quickly bring the vehicle interior to the set temperature. Setting the temperature higher or lower than the comfort setting will not heat or cool the vehicle faster than when set at the desired temperature. During cold weather, the fan will not operate in the FLOOR position until the engine reaches a predetermined temperature.
Click to expand...
 
You certainly can use "floor" for heat without running the AC compressor, but you may find the windows may start to fog up, especially with a car full of passengers.
 
Ok, sorry its been so long since I had my car, and I hardly EVER used the hot air, but is there a "heat" button, and what does it do? Defrost and Floor?
 
Left to right, the buttons are...

MAX AC / VENT / PNL-FLR / FLOOR / FLR-DEF / DEFROST

Air Discharge Locations

OFF-Pushing OFF button stops all systems operations.

MAX A/C-Pushing MAX A/C button provides cooling with recirculated air through the instrument panel outlets. The compressor will operate.

VENT- Pushing VENT button provides outside air flow through the instrument panel outlets. The air can be heated but not cooled in the vent position. The compressor does not operate.

PNL-FLR-Pushing the PNL-FLR button allows outside air to be discharged from both instrument panel outlets and the floor outlets. The compressor operates to dehumidify the air.

FLOOR- Pushing FLOOR button allows outside air to be discharged through the floor outlets. The air can be heated but not cooled in this position. The compressor does not operate.

FLR-DEF-Pushing the FLR-DEF button directs outside air out the defroster outlets and the instrument panel outlets. The compressor operates to dehumidify the air.

DEFROST-Pushing DEFROST button directs outside air out the defroster outlets against the windshield. The compressor operates to dehumidify the air.
Click to expand...
 
So... Why is his compressor coming on in floor mode? The cycling is either the low or high pressure switch, but when the compressor turns off the pressures equalize and the pressure switch is satisfied and allows the compressor to come on again. Why your compressor is coming on in FLOOR mode, im not sure. Either way if the compressor is on then it should not cycle off unless the fan is low or off, and in your case, if the heat is on as well (heat always wins) it should raise the suction (low side) and should not cylce off the compressor. Unless its getting so much heat from the heater coil it may also cycle off on a high side pressure switch and may not be a refrigerant problem at all , more like a failure in the main unit in the dash
 
Last edited:
BlackMark8 said:
So... Why is his compressor coming on in floor mode?
Click to expand...

I re-read the entire thread and didn't see where that was stated. It was said when the "heat is on". There is no "HEAT" function - it is an automatic temperature control system. Press the red button to raise the temp and press the blue button to lower the temp. The temperature is adjustable in any mode.

As was said before, the AC compressor runs in all modes except OFF, VENT and FLOOR.
 
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