I have a 94 F150. The truck blows heat when switched to AC or Max AC. I hooked up the gauges and it reads around 40psi so it should atleast be blowing cool air. The compressor is kicking on. I can not heat any noises when switching the **** from heat to cold. (I can always hear the cable moving when switching from heat to cold in my car.) I have not had much time lately to look further into it yet other than the 5 minutes I have spent already. I am thinking the temp control cable is broken or seized, A vacuum solenoid is bad, or the blend doors are hung up. Ac is not my strongest subject. Any other thoughts before I start checking into it? Thanks

 

I forget which blend door is temperature change, but I would check them first. Not sure if the temperature door is cable controlled or vacuum (probably cable). remove the bezel around the *****, then the **** unit/face itself to verify that the cable moves when you turn the temp ****.

 

The cable for the blend door attaches behind the glove box. If you got 40 high and low, no you're not getting any cold air from that.

 

40 on the high side. I believe the cable runs from the climate control head, through the firewall, and over the air box. I believe there is also a vacuum solenoid but it dosent switch to defrost while under a heavy load, so I believe that is fine. Im going to check out the cable today on my lunch.

 

Needs a lot more freon if you want it to even start getting cold.

 

I was just going by what the can said. Ill charge it up more when I get home. One vacuum solenoid is working, gotta pull the glove box when I get home and check that one.

 

The can? The can only reads the low side.

 

If your compressor is running feel the line going into the firewall. It should be cold and sweating. the smaller line going to the condenser coil in front of the radiator should be the opposite, hot. If this is the case you at least have a semi-working system and I would concentrate on the blend door.
BTW, you can't just go by the low pressure. You need a full set of guages and the specs for your system depending on ambient temp.

 

Or, you can just add the correct amount of freon if the system was empty.

 

You still need guages to tweak the refrigerant level. You don't know how much oil/dye is in there, maybe the orifice doesn't flow quite like it should, maybe one of the coils is dirty. With an F150 system that method would probably work OK, but with some smaller capacity systems you have to get it close to the exact ounce of refrigerant. I'm just trying to discourage this guy from buying 3 cans at Autozone and throwing them in.