Recently The A/C is defaulting to defrost but blowing cold. Any time this has happened in the past it was a loose vacume line usually the one which controls heater hose valve (grey hose) i have checked vac. system and i cant locate any leaks. Any suggestions would help.

 

Start with the HVC FAQs (see signature).

If 4x4, check the vacuum pulse solenoid on the passenger fender well. It's a common leaker.

 

Thanks PROJECTSHO89 i went over that part but will examine closer

 

Skip all the troubleshooting and just replace the main a/c panel. Had same thing and thats was the fix

 

Nonsense.

The "main a/c panel" is only one of multiple possibilities. Replacing it first without doing any troubleshooting is a foolish waste of money.

ALWAYS do your troubleshooting unless you have money to pi$$ away.

 

If your solution is to throw parts at stuff with out checking first be my guest. But it's foolish when the more likely solution will cost < $5.

To the OP, more than likely you have a vacuum leak somewhere. Trace all of your vacuum lines. If you have ESOF 4x4, check the wheel wells first, the vacuum lines to the hubs are a common culprit.

 

WOW...that sure is somthing I wouldnt do first without doing some troubleshooting.

 

^Only if you have cubic money.... .....and that still may not fix the problem.^

As mentioned, you have a vacuum leak somewhere. The AC system runs off of vacuum. If there is not enough vacuum to run the system, it defaults to blowing out of the defroster vents as a safety measure.

 

Would the "vacuum pulse solenoid" also be called the solenoid vacuum valve? If not - do you know the part number by chance? Thanks!

 

Still tracing vac. leak but have not yet located. If the vac. motor stops pumping after the key is on should that indicate the system has reached normal vac. If the vac. motor keeps running then a leak exists. Mine is shutting down only after about 10 to 15 seconds and does not restart?

 

how much vacuum is it pulling?

it could be a bad pump.

 

I noticed the same issue yesterday... A/C switching from panel to defroster vents under moderate acceleration/load... started poking around this evening... found a loose vacuum line... has a yellow tube on the end of it about 6" long... cannot find where it goes to... somewhere on the passenger side of the engine, based on the length of the hose... don't mean to hi-jack, but anybody got any thoughts???

I guess a pic would help, eh? Will try to shoot a few pics tomorrow when I've got some daylight...


BTW... it's a 2000 F250 4x4 V10...

 

Look at the reservoir too, it could be leaking. And if there are any lights not working on the rear end ie. Reverse or brakes, check the fuse

 

OK.... I am off the defrost vent. I was tracing all vac. lines and noticed there was no vac. in the line (black plastic) off the solenoid valve? bolted to the passenger side engine comp. near the battery. I took the vac. line which tees off the res. tank which goes to the hubs and connected it to the black plastic hose which runs with grey line into cab. I have cold air where it should be now. I take it the solenoid valve is junk. I have not checked electrical yet. Does anyone know what current comes in the three wires which plug in.

 

Just connect a short vacuum hose to the inlet port of the valve and blow in it. If it leaks, it will be obvious.