Air only blows on defrost???

[miner999r]

Had the problem a few weeks ago. Just about to go on vacation, had a u-haul trailer hooked up and then only blow through defrost. This is Thursday afternoon. Went to dealer, service guy said no openings till next Tuesday, but said if I could leave it they could look at it right now. A short while later they called to advise a vacuum pump was needed and the good news was they actually had one in stock. Had my truck back an hour later and could start my trip in the morning. I am real happy with the service that Steve Marshall Ford provides in Campbell River and Nanaimo on the Island. Yes there are some good dealers out there.

[jakesnake_sxr]

hey man got an 05 didnt see your post im having the exact prob you are i priced a pump witch i was only able to find at the dealership,its $233.

[foul1]

Well kind of happy to report that it just started to work properly on its own. Thinkin its going to return but will just have to wait till it does it again I guess.

[Scubadoo]

I have just bought my first Ford diesel pickup, and it had the same problem. I took it to a friend that owns a shop, and happens to own a 2002 F250 also. He told me the problem was my vacumn pump. I replaced it, I had to buy the part from the dealer, no one here had one, and it fixed the problem. I did have another problem come up the other day. When I put it in four wheel drive the AC went to the defroster. Another friend, actually his brother, that has had three different F250 diesels told me his solenoid went out and it did the same thing. So, both of those are under the hood, on the passenger side fender. They are both easily changed out by you and there is no need to take it to the dealer. You will probably have to buy the parts there though as the local parts house did not have them for me.

Good luck

[Beachbumcook]

OK guys.... here is my problem that just started tonight.

1) My AC works fine and blows out the front vents.

2) When I put my truck into 4WD (ESOF) the hubs lock and 4WD engages, but then my AC defaults to the defrost only mode.

3) If I turn off 4WD, the air still comes out the defrost mode... but if I shut off the main Enviromental control unit and turn back on it works just fine and blows air out the front vents as it should.

With this set of circumstances, where would I even look or have the dealer look? They just removed and repainted my front bumper and I just picked it up today... so I think (not sure) it may be related?

With the circumstances above, is my 4WD pulling to much vacum pressure and this is why the AC then defaults to the defroster mode... but will return to normal when I shift out of 4WD and turn the AC controls off and then back on?

What is leaking or has come loose????

Thanks,

[bismic]

Originally Posted by Beachbumcook

OK guys.... here is my problem that just started tonight.

1) My AC works fine and blows out the front vents.

2) When I put my truck into 4WD (ESOF) the hubs lock and 4WD engages, but then my AC defaults to the defrost only mode.

3) If I turn off 4WD, the air still comes out the defrost mode... but if I shut off the main Enviromental control unit and turn back on it works just fine and blows air out the front vents as it should.

With this set of circumstances, where would I even look or have the dealer look? They just removed and repainted my front bumper and I just picked it up today... so I think (not sure) it may be related?

With the circumstances above, is my 4WD pulling to much vacum pressure and this is why the AC then defaults to the defroster mode... but will return to normal when I shift out of 4WD and turn the AC controls off and then back on?

What is leaking or has come loose????

Thanks,

You have a vacuum leak from one or both of your 4WD hubs. Check the vac. hose on each spindle, they are known to crack or fall off.

[Beachbumcook]

Originally Posted by bismic

You have a vacuum leak from one or both of your 4WD hubs.

OK... but if I do... then how are my hubs locking in and staying locked?

How can I tell if it is my hubs vacum line(s) or the vacum pump itself?

(I have zero experience with this issue as it has never affected me before)

[bismic]

You should be able to tell if you have a bad hub by locking it in auto 4wd w/ the hubs in auto then try to spin each front axle... If one of them spins then that is the one that is messed up and not sealing..

[bismic]

Here is a good general procedure for troubleshooting a vacuum issue:

First locate the vacuum pump on the passenger side fender well.
Make sure it works by listening with the key on should be vibrating.
Next unplug the vacuum harness at the resevoir an cover with a finger to make sure it turns off.
Install a vacuum pump into the hose (the pump should pull 25+ " of vacuum within seconds).
If that is ok, then reconnect the pump line to resevoir inlet and vacuum pump to outlet to make sure the resivoir will hold vacuum.
If thats good, follow lines to the "tee" were they split. You will see two lines ..... one goes to the front end and the other to the dash.
Disconnect the lines and hook up the vacuum pump to each line, one at a time.
Pump the gun to 20 " or so and monitor for 5 minutes to insure they do not drop vacuum.
90 percent of the time the problem is the line going to the front end.
If the front end is causing the problem, then jack up the front end disconnect the vacuum lines to front knuckles.
Pump to around 20" of vacuum while spinning tires to see if it drops vacuum.
If either one does, then add 3-5 psi of air to the knuckle and spray with soapy water to find the leak.
You can either fix the leak or cap off the line up top and run your hubs manually.
If the dash and the front end lines hold vacuum, then cap both lines off with a golf tee or equivlant.
Pump the line from resevoir to vacuum control solenoid to find the problem.
Also if the grey vacuum line that goes either to the hot water shut off in the heater hose or to the evaporator case is hanging loose, it should only cause a problem in max a/c.
If the problem is in the dash just keep unhooking vacuum lines and plug one end and pump the other until you find the leak.

[Beachbumcook]

Originally Posted by bismic

Here is a good general procedure for troubleshooting a vacuum issue:

First locate the vacuum pump on the passenger side fender well.
Make sure it works by listening with the key on should be vibrating.
Next unplug the vacuum harness at the resevoir an cover with a finger to make sure it turns off.
Install a vacuum pump into the hose (the pump should pull 25+ " of vacuum within seconds).
If that is ok, then reconnect the pump line to resevoir inlet and vacuum pump to outlet to make sure the resivoir will hold vacuum.
If thats good, follow lines to the "tee" were they split. You will see two lines ..... one goes to the front end and the other to the dash.
Disconnect the lines and hook up the vacuum pump to each line, one at a time.
Pump the gun to 20 " or so and monitor for 5 minutes to insure they do not drop vacuum.
90 percent of the time the problem is the line going to the front end.
If the front end is causing the problem, then jack up the front end disconnect the vacuum lines to front knuckles.
Pump to around 20" of vacuum while spinning tires to see if it drops vacuum.
If either one does, then add 3-5 psi of air to the knuckle and spray with soapy water to find the leak.
You can either fix the leak or cap off the line up top and run your hubs manually.
If the dash and the front end lines hold vacuum, then cap both lines off with a golf tee or equivlant.
Pump the line from resevoir to vacuum control solenoid to find the problem.
Also if the grey vacuum line that goes either to the hot water shut off in the heater hose or to the evaporator case is hanging loose, it should only cause a problem in max a/c.
If the problem is in the dash just keep unhooking vacuum lines and plug one end and pump the other until you find the leak.

Thanks.... since the dealer removed, re-painted and re-installed the front bumper... I am assuming they knocked a line loose? I will take it in tomorrow AM and have them look at it.

Have a great evening.... thanks.

[imgman]

Welp.. I have the same problem on my '03 F-250. My AC or heat only blows out the defrost. Been that way since I bought it used a couple years ago. Now I live in a hott climate and it needs fixed. My 4x4 works fine as I used the heck out of it this last weekend. My vacuume pump runs and shuts down on its own and also shuts off when I remove the line to the reservoir and put a finger on it. Not much vacuume from what I feel, but I dont know what 25" feels like (no pun intended But of course my hubs work so I assume the pressure is good. My blend door works as I can switch between hot and cold AC thru my defrost so its got enough vacuume to run that.

I always assumed it got dust in the system (it lived its whole life in the woods as the PO was a pot grower) and the door that flops the air from defrost over to vent was stuck. My old Navigator (Expedition) had a simiilair problem.. the door would squeek and groan but eventually change over from vent or defrost.

I guess I will check out the vacuume solenoid on the fender next. Anyone know how to check that? It looks like it controls the vacuume to the dash and could be the culprit. If I knew what triggered it, to turn on I could feel for the vacuume on or off at the hose to the dash when the pump is on. Maybe I can just put 12 volts to it and see if it opens up ???

One would think if there is a vacuume leak somewhere, that pump would keep on running and running... or at least turn on once in awhile without using anything.. and of course it still has vacuume to run the hubs and blend door...

I will let ya'll know what I find out. Lemme know if anyone knows how to test that solenoid.

[69cj]

Originally Posted by 12ozd

Low/no vacuum will cause the htr. & a /c to default to defrost only.

Vacuum pump failure and vacuum line leaks are a common problem.

The vacuum pump is on the right (pass.) side fender.

Make sure you have power to the pump, if not check fuse.

If you have power,disconnect vacuum line and feel for vacuum.(hear pump run)

If no vacuum, replace pump. If you feel vacuum, then there is a leak.

Most common area for leak is vacuum hoses to; and front hubs (hence question about 4x4 earlier).

If pump is good, and no leaks,time to go inside the dash (doubtful).

Another common leak point is vacum line behind the glove box.

[imgman]

FIXED! I wish I had looked into this earlier. All it was was the vacuume lines were crossed. The solenoid was attached to my climate control. So that means for the last two years since I owned the truck, my hubs have been locked and my defrost only has worked. I wished I had looked at this earlier

[Beachbumcook]

Will be replacing the vacuum solenoid this week.

I disconnected the front hubs line coming out of the solenoid valve (at the first 90-degree T) and plugged it with a golf-T. My problems still ocurred... so I know it was the solenoid and not my front hubs or seals.

When not in 4WD, my environmental controls and vents all work fine... so it is just the solenoid when the ESOF button activates the Pulse Vacuum Solenoid Valve.

I bought part # 7C3Z-9H465-A for $46.00 or $48.00 (can't remember now) from my dealer (that I have a relationship with)... normal price is between $60 - $70.00 if they don't know you or just are greedy.

Below is a photo that is labeled with all the vacuum line connections (on passenger side fender). I got this photo from another user's post in the 7.3L section... so if you see it elsewhere... credit should be given to him and not me... but I think you will all agree it is a great resource/photo.

Good luck,

[bismic]

Originally Posted by Beachbumcook

Will be replacing the vacuum solenoid this week.

I disconnected the front hubs line coming out of the solenoid valve (at the first 90-degree T) and plugged it with a golf-T. My problems still ocurred... so I know it was the solenoid and not my front hubs or seals.

When not in 4WD, my environmental controls and vents all work fine... so it is just the solenoid when the ESOF button activates the Pulse Vacuum Solenoid Valve.

I bought part # 7C3Z-9H465-A for $46.00 or $48.00 (can't remember now) from my dealer (that I have a relationship with)... normal price is between $60 - $70.00 if they don't know you or just are greedy.

Below is a photo that is labeled with all the vacuum line connections (on passenger side fender). I got this photo from another user's post in the 7.3L section... so if you see it elsewhere... credit should be given to him and not me... but I think you will all agree it is a great resource/photo.

Good luck,

Nice troubleshooting - appreciate the post!