dashboard A/C on the fritz

ernie1 wrote:
Wow! It blows my mind what sort of info is given out. Having been an ac tech for a couple of years I have this bit of advice to the op: if you have to depend on the advice you glean from this site it's is obvious that you don't know enough nor have the proper equipment to correct your problem and should take it to a professional to have the ac repaired. This will save $$$ and you won't expose yourself to the dangers of exposure to refrigerants.I will have nothing further to say.

What exactly are the "dangers of exposure to refrigerants" The op wants to know some basic refrigeration techniques to which he did receive some. Now if he were asking how to recover and replace refrigerant that's another story. Installing gauges does not expose one to your dangers to exposure statement. He is checking to see if his mixer door is working properly, big deal.

Wow! It blows my mind what sort of info is given out. Having been an ac tech for a couple of years I have this bit of advice to the op: if you have to depend on the advice you glean from this site it's is obvious that you don't know enough nor have the proper equipment to correct your problem and should take it to a professional to have the ac repaired. This will save $$$ and you won't expose yourself to the dangers of exposure to refrigerants.I will have nothing further to say.

classctioga73 wrote:
So this morning I took the rv for a ride. It blew cold air for about 5 minutes then just regular temperature air. I turned the knob to off and tried to turn it back on and no air came out at all. I turned the setting to floor and it worked. I turned the knob to off and back to vent and no air, then I turned it to floor and no air
Are these symptoms all related to a bad blend door box??

It still has freon in it, otherwise it wouldn't cool at all. If it were my rig here is what i would do.

Open the hood engine off, locate the AC compressor and become familiar with the clutch mounted on the end. Have an assistant start the rig then turn on the A/C. See the clutch engage. Now have them duplicate the scenario that you described, always watching the clutch. If they experience no air and the clutch is still engaged then I would focus on the door mixer. If the clutch disengages it most likely has air in the system and is building up high head pressure in the compressor. They kick off around 300 psi on refrigeration systems not sure on autos.

Easier way is to go to auto store that loans tools, you need gauges for 134a. You can't put them on wrong, the ports are sized differently.Install those start the engine and observe the pressures. Look up a basic R134a temperature pressure chart and you can see the numbers that you are aiming for. Ambient temperature changes everything. They offer cans now with a hose attached that works well however an air conditioning system does not use freon like an engine uses oil, you have a leak somewhere. One of my cars used a can a year. With the gauges on you can observe the high side(big numbers PSI) and the low side . If the low side goes into a vacuum you need freon, if the high side goes to a big number and the clutch disengages then you have an issue with air in the system.

The gauges won't blow up. Be sure they are in the off position before you start and leave them there. Check for that sight glass too. Usually mounted low, like bottom of radiator low about dime size glass. If the engine has been running for 5 minutes and there are bubbles, you have troubles.

I think that the ac system is possibly low on refrigerant and the unit is acting like it is. When the system is first started, the low side will have about the same pressure as the high side until it is run for awhile and the low side will continue to drop in pressure until approximately 20 psi at which point a low pressure cut out switch will disengage the clutch on the compressor to protect it from damage. Allowed to sit for awhile, the low side pressure goes up past the low pressure cutoff point and the unit will work again. A set of refrigerant gauges will confirm the state of charge or, if there is a sight glass in the system, look for bubbles. If the system is low on refrigerant, be sure you know what you are doing before attempting to recharge it.

So this morning I took the rv for a ride. It blew cold air for about 5 minutes then just regular temperature air. I turned the knob to off and tried to turn it back on and no air came out at all. I turned the setting to floor and it worked. I turned the knob to off and back to vent and no air, then I turned it to floor and no air
Are these symptoms all related to a bad blend door box??

classctioga73 wrote:
J-d
Where is this part located under the hood or behind the setting knobs

I just looked it up on u tube using these key words blend door removal 2000 Ford E450

There is a video, many actually, that shows it behind the glove box. Access and removal takes a minute or two. He said that video covers Ford heavy duty models up to 2007.

J-d
Where is this part located under the hood or behind the setting knobs

Your Heat Vent Air Condition (HVAC) has vacuum control for Mode Selection. Face, Floor, Vent, Recirc, Defrost, etc. Notice I left out Temperature. That's controlled by an electric motor managed by some electronics. The motor looks like this where that white button looking thing is the outboard end of a shaft that positions the Blend Door. I show the connector side to let you see it's electric not vacuum.

The Heater Core runs full hot full time. So does the A/C Evaporator. The Blend Door "Blends" those two extremes to give you the feeling you desire by turning the knob from Blue to Red.

So it's possible something is causing that Blend Motor to go to extremes. That and a couple A/C issues that others'll probably cover.

On my truck camper I had a noise one year when traveling and nothing happened. The next year same noise and the air conditioning stopped working. Everything continued on but the air was hot - zero cold, a few minutes later it was back. A couple minutes after that it was off again and never came back on. We returned home and took to my mechanic and he said the bearings on one of the pulleys went and caused the belt to stop turning, replaced pulley, tightened belt and all was fine again.

Tiger4x4RV wrote:
My Chevy did something similar a few times on long extremely hot drives. A/C kept blowing, but starting putting out boiling hot air. If I stopped, turned off the engine, and restarted in a couple of minutes, usually I got cold air again. Googling around said it might be a stuck blend door in the A/C system. I never did anything about having it repaired and it hasn't happened for several years.

If you get cold air at all, you still have refrigerant in your system.

Quite possibly the compressor is shutting down due to air in the system causing high head pressure or the clutch is disengaging after it gets hot. . Refrigeration/air conditioning systems do not use freon like an engine uses oil. If it is low on freon it leaked out somewhere. There are also possibilities with pressure switches. Try to locate the sight glass and look for air bubbles, you should not have any, it should be clear. Check around air conditioning fittings for oil seepage, that is an indicator of a leak. As was said, if you still get cold air your charge is good, your electrical components need checking.