A/C and Heater control problem
 

I have a 2007 F-250. The controls for the climate control have gone haywire. When I turn everything off the defrost blows full blast. The temp controls, auto, and blower functions don't seem to work either. Basically nothing works as it should. Is this a common problem? Any ideas? Thanks.:(

does your truck have ESOF? if so is it working?

It does, but I haven't tried it since the A/C problem came up. What are you getting at?

if you have a vacuum leak within the esof system it makes your heat only blow out the defroster.

The climate control system is powered by vacuum. If there is insufficient vacuum to operate the system, it defaults to full fan blow out the defrosters. This is a very strong indication that you have a vacuum leak somewhere in your truck.

The most common place for this leak to occur is the ESOF hubs, which are also vacuum powered. Check the hoses leading to the hubs and the hub seals. The second most common cause is a failure of the vacuum solenoid, which controls ESOF and the heating system. Third most common area to look is all the vacuum hoses in general, look for rot, tears or a hose that just fell off.

My 2006 had a problem also and I have manual hubs. The climate control was not working at all and the fan would only blow when I turned it on full blast. It was covered under warranty since I had just bought it. They didn't tell me what the problem was. Sorry I don't have anything more for you. 8D

Thanks for the replies, guys. I'm calling the dealership now. I haven't had the truck 3 years yet, but the mileage is 36345. I believe it was a 3 year/36,000 warranty....figures.

Anyway, I believe it is an electronic problem since turning everything to off doesn't work.

The ventilation door is vacuum operated. 0" of vacuum (atmospheric pressure) is the defrost setting, so no vacuum or any leak will result in the ventilation going to defrost for a couple of minutes each time you went into or out of 4wd. Since the problem is constant, there are a few possibilities. I am in no way a professional mechanic, but I did stay at a Holiday Express last night :-X14! Just from what I've experienced and what I've read I'll list a couple of the more common possibilities that come to mind:

1. You could have a failed solenoid (opens/shuts to allow vacuum to the hubs to lock or unlock them) which is always appying air to the hubs along with a vacuum leak in the ESOF system for the hubs.
2. You could have a vacuum leak somewhere in the rest of the system (that is for the HVAC system).
3. If your truck is a diesel, it has a vacuum pump that makes the vacuum (the gassers get it from the engine). You could have a vacuum leak that has caused the pump to continuously run which could have blown a fuse or killed the pump.

Just some thoughts. You can usually check the vacuum pump (if you have it), by listening under the hood when you place the ignition key in on (before you start the truck). While you are waiting for the "wait to start" light to go out, you can usually hear buzzing away to build vacuum.

There is a resistor bank (or ladder or tree or whatever you want to call it) that provides different resistor values based on the fan speed position you have the switch in. Many of the loops have common wiring so one wire going bad to one resistor can affect several speeds. Sounds like your fan speed resistor circuit had an open wire somewhere (or damaged portion of the bridge) and only the high speed portion of the circuit was still good.

I'm not too mechanically inclined so I made the appointment for tomorrow. The 4wd seems to be operating just fine. Oh well. Life happens.