Why would the air conditioner of a 1999 Jeep Grand Cherokee not work even when the light is on and the dials are on the coldest settings but the heater works fine?

Answer 1

It could be any of a number of reasons. Such as: You are out of freon. Your compressor doesn't work. Really the only thing your light being on is telling you is that the fuse isn't blown. And your heater has nothing but the blower motor and duct work in common with the air conditioner. I would suggest a good mechanic or a Haynes or Chiltons Manual if you are mechanically enclined. Good luck. Jeeps are notorious for the AC going out more than likely your heater core box is full of debris and the fore you have to go to the dealer ship and they cahrge you $850 to clean it then they tell you how you need a new condenser and that is another $850 this has happend 2X to me my suggestion is get rid of it additional info: there are a number of posts on Wiki concerning AC problems with Jeep GC's. My experience is that you probably are having a problem with a clogged drain tube leaving the evaporator box. This is assuming that your freon system is fully charged. I would have a reputable AC tech check the freon first and then turn my attention to the drain. The previous answer is correct about the debris in the evaporator box and it is a result of extremely poor engineering on the part of Jeep. Keep looking on line and you will find out more.

Of course, you have to be sure that the compressor is working, the system is charged and things are getting cold. A simple check of the refrigerant lines going into the firewall with your hand will give you an indication of whether the system is cooling or not. If the lines are cold, your problem may be with the blend door or re-circ door. The blend door diverts some or all of the air flow through the heater core. When this door breaks, you lose control over the air flow and can see problems with both heat and AC. Usually the broken blend doors fall to the bottom of the heater box on the GC and block heat. However, it is not uncommon for the doors to fall crooked and kill the AC function also. The re-circ door is also susceptible to failure. This door chooses between external and internal air going into the system. When it fails, you are contstantly pulling hot, outside air into the system, greatly reducing AC efficiency. Both of these fail modes are common. Check the HeaterTreater listings on Ebay for more diagnostic information and an inexpensive fix for the problem

Answer 2

This could be several problems. It could be a bad fuse, a bad switch, a bad sensor at the A/C lines, it may need to be charged. I would check to see if it needs charging first. But if it does, it means you have a leak somewhere that needs fixing. Hope this helps.

Let's not assume an a/c problem if the air is not blowing. This is usually due to a burnt out blower motor resistor. The various speeds of the blower are controlled by this resistor pack. It is cheap to replace and is usually located behind the heater/AC controls on the dash. This pack can fail in different ways to where some blower speed positions work and others don't. If there is no air blowing at all I would check it.

Answer 3

The system has a blend door that diverts some or all of the air flow through the heater core and regulates temperature. The door has a metal axle and connects to a DC motor that has a metal coupling. In a fit of brilliance, Jeep decide to connect these two metal components together with a plastic connector. The general problem when you lose control over temperature is that the plastic connector broke.

The actuator motor is on the bottom of the plenum box under the passenger side dash next to the transmission tunnel. If you remove the motor and pull straight down on the plastic connector, you can check for cracks or breakage. You should be able to regulate temperature by just turning the axle with your fingers. There is an aftermarket metal connector for the system.

Answer 4

In all likelihood because the coolant leaked out.