My air conditioner on my truck works really well most of the time. The air if very cold. However, out of the blue from time to time, it will turn off and the air will come out somewhat hotter than outside. I can't link this to any behavior or specific circumstance. For example, it is not connected to whether I am accelerating or not, and it doesn't seem to be related to the normal on/off cycling that they do. After a little while it will start blowing cool again. Is this perhaps a "Freon" level issue. Any suggestions will be helpful thanks.
Your problem and limited desciption just raises more questions.
Is AC system auto or manual?
Exactly what settings is AC on if manual, fan, blower, etc?
What is outside temp/weather like, hot and dry, humid, . . . . ?
Just guessing- Sounds like system is 'freezing up' then going through a thaw, then working normal again.
If it does this all the time, every single time it's on, with predictable regularity, it could be low refrigerant, or bad pressure switches.
If it's a sometimes thing, it's connected to the climate controls (if auto system), or you're running too low fan speed and/or AC instead of Max AC.
OK, it's a manual, and I get the problem whether it is on regular AC, MAX AC or defraust(sp). I am located in the Greater Washington DC area, and the weather has been pretty mild. Mid 80's to mid 90's and moderate to high humidity. However, it will do this regardless of the conditions. I usually run the AC most of the time at highway speeds because the engine heats up the incoming fresh air. I hadn't thought of the freeze thaw issue. I could not show a person the problem unless they went for a reasonable ride with me. For example, it would be tough to show a mech, this issue, because it doesn't happen on command.
My 95 did the same thing. It would work great for an hour then not work for a week, then work great for a couple weeks then not at all for a day or two - you get the idea. CLICK HERE to go to a thread I started when I fixed mine. It may or may not be your problem but is a way to get started.
The heater core always has a little coolant running through it so the air coming through will be warmer than outside air. There is a fix for it using a vacuum operated valve from another truck - if I can run down a link to it I will post.
Dave / Believer45
Last edited by believer45; 07-04-2004 at 02:01 AM.
I found the instructions in an MS Word document I have saved, cut and pasted here, for the heater core hot water shutoff modification to our trucks to keep the air conditioner from having to overcome some heat in the heater core to cool the incoming air.
This mod will stop the flow of hot water through the heater core when the AC controls are in the MAX setting and the OFF position providing cooler temps and preventing the hot pocket of air down by your feet. I went to NAPA and asked for the 'hot water shut off valve' from a 1990 Ford Ranger with a 4.0 V-6, I also got 4 - 5/8 hose clamps, a couple feet of 1/8" vacuum line and a 1/8" plastic "T" for the vacuum line. To begin the install loosen the cap on the radiator overfill to remove pressure from the system (do this while the engine is cool). On the passenger side of the engine compartment there are two 5/8" hoses that come from the firewall and continue to the engine, these are the heater hoses. Cut the hose closest to the drivers side (It doesn't really matter where, I did mine about 6 inches after the firewall). Then holding the 'shut off valve' with the vacuum controller towards the passenger side install the portion of the heater hose coming from the cab to the top left nipple on the 'shut off valve'. Tighten the clamp. Install the portion of the heater hose coming from the engine to the top right nipple and tighten the clamp. Next cut the heater hose closest to the pass side in the same location as the previous. Install the portion coming from the cab on the lower left nipple, tighten the clamp. Now install the portion going to the engine on the lower right and tighten the clamp. Measure out how much of the 1/8" vacuum line you need to reach from the bottom of the vacuum canister on the shut off valve to the white vacuum line on the pass side that goes to the vacuum operated door underneath the pass side cowl. Cut that white vacuum line and splice in the 1/8" plastic "T". Then run the 1/8" vacuum line you measured out from that plastic "T" to the nipple on the bottom of the vacuum canister on the shut off valve. It sounds more complicated than it is. Once you do it the job will seem real simple.
This is from Steve Baz's informative site, linked HERE.
Hope this helps out.
Dave / Believer45
Last edited by believer45; 07-04-2004 at 01:54 AM.
If you find that the compressor is disengaging at times randomly and staying off too long, I have found that the high pressure switch is often the culprit. It is mounted to the high pressure line coming off the compressor and the connector will get hot and burn the pin in the switch and the connector itself. This requires replacing the switch and he connector or the pins in the connector. If you cant find a replacement connector or pins you can bypass the switch by splicing the wires together. That will just leave you with no cut out if the cooling fan ever stops working and high pressure maxes out. A decision you would have to decide to risk or not.
Double thanks for the Ford owner's site and info about the heater core designed in problem.
Have you (or anyone) any idea if this heater core thing is still the system normal for new trucks (04), or is only in certain models/engines?
I just thought the flow through the heater core was shut down as in older models of trucks, the why of a continuous hot water flow is puzzling, anyone know of a reason the engineers would have this happening on purpose no less. There's got to be some reason for this.
Only logical thing I can think of would be to keep a flow going through the heater core to prevent core erosion from happening (maybe), or possibly to dry the air to prevent humidity in the cab.
But why you'd force the AC air flow to have to overcome this heat generation doesn't make sense.
I know Ford engineers/designers are paid to have ideas, would just hope they'd have to be good ideas.
I don't know why it is designed as it is nor do I know if the new trucks are set up the same way as the older ones. I do know my A/C works more like refrigeration (now that I fixed it) without the modification but the vent is warmed a bit so I will do it when I get the chance.
I have a 2000 F250 and was driving the other day and noticed that my ac was blowing hot air just briefly. It would happen for oh 10 sec at a time. Noticed it 4 times. Never noticed it happening before. The ac in on of the ambulances (2002 E350 7.3L) freezes up from time to time takes forever to thaw out. Goes out for 30 min at a time.
Thanks for the help. All the fuses are fine. That was the first thing I checked. I guess I will check the air control doors and then on to the vacuum lines and controls. Hopefully, this will solve the problem.