Jeep Cherokee Air Conditioner Not Cold Enough

Reader Question
AC on my 1998 Jeep Cherokee, 4L engine is not as cold as before, even at highway speed if there is significant sun load. Was going to add freon with store bought kit that had a gauge.

When I checked low side pressure with gauge it read in the green (35psi) so I did not add freon. Using a good thermometer I could only get 67 degree air out the vent with 88 degree ambient temp and 55% humidity. AC on full at 1500 rpm.

Should get 35-40 degree below ambient according to my Hanes manual. Compressor stays engaged as long as cooling is called for. Any thoughts?

Hey there RV,

The first thing that comes to mind to me is there might be outside air or hot air from the heater core getting into the evaporator case. Sometimes the heater control valve or the “blend door” inside the dashboard will allow hot outside air….or worse hot air from the heater core to enter the a/c evaporator.

It is very hard to make outside or air from the heater case COLD. I would feel both heater hoses going to the heater case, one will be much hotter than the other if the valve is working properly.

If both hoses are HOT, then take a pair of vice grip pliers and block off the hoses so you restrict the flow of hot coolant to the heater core.

This will hot cause the engine to overheat or cause any other cooling system problem. You can drive the vehicle on the freeway with the pliers attached to see if that helps lower the inside duct temperature. If it does you might need a new heater control valve.

Also make sure there is no OUTSIDE air entering the a/c case, and the a/c control is set to MAX or Recirculation. If both of those items check out ok, you might want to try adding a can of Freon and see if that helps.

Sometimes just a little bit of Freon can help drop your numbers substantially. I have seen problems with the dash control that cause the “blend door” inside the dash to stick open in the FRESH air setting, which sucks hot outside air into the a/c evaporator case.

If it’s 90 degrees outside and you are sucking in and trying to cool outside air…the best you will get would be about 65 degrees out of the ducts.

Other things to check would be:

1. Make sure the engine is not running too hot or overheating

2. Check the electric condenser fan and make sure it is coming on at idle, and/or check the fan clutch if equipped.

3. Check to see if you have a “site glass” on top of you’re a/c drier, there is sometimes a small glass window on top of the drier (which is probably located up near the condenser) if you see small bubbles in the glass window you are probably low on Freon. Some models have this site glass others do not, not real sure if you do or not.

Austin C. Davis

Posted in: A/C and Heating

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