# No air coming out of floor vents on my F350.



## mklawnman

I have a 99 F350, and when I turn on the vents for the floor vents the air doesn't come out by the floor, it only blows out by the defrost vents. IS there some baffle inside the vent unit thats not opening or closing? Or could it be the switch in the dash to change what vents to have on? 
Any help would be appreciated.
Thanks
Matt


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## trickynicky17

I'm not 100% sure on this but judging by your sig im assuming the truck is a diesel, i had the same problem on my 04, don't know if 6.0 or 7.3 is different but there is a hose that comes off on the vacuum pump that makes the vents switch and it comes off on a lot of trucks. Open the hood and look at the passenger side towards the back and see if there is a vacuum hose flopping around in there.


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## mklawnman

Its a 7.3L Diesel. Ill have to check those vacuum lines hope its obvious cause I know there are vacuum lines for the 4x4 as well so.


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## trickynicky17

Yeah check that first, if its blowing out but not changing where it's coming from that's gotta be it.


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## tugboat609

Had similar problem with a Dodge I used to have. Was vacuum line.


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## dieselss

Also check behind the glove box. That's where the blend doors are. You can see them easily working or not.


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## hunt 444e

start your truck turn heat on go under hood passenger side by the firewall is your mode door actuator little black box about 2x 4 or so if thats clicking or making noise take it off throw it out get another you probably washed it and got water in it or something :


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## fordsuvparts

IF you will look under the passenger side of the dash there is a vacuum plug that can come unplugged and it will cause the floor vents not to work. This happened last winter on 2 different trucks someone jammed there feet under and pulled it loose.


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## mklawnman

Well I checked the vacuum lines on the passenger side under the hood but everything looked fine. I did see where the lines go into, some box, but I dont think anything is clicking or if any vents are. All settings for the vents seem to default to the defrost, A/C, everything. 
I will check under the dash on the passenger side and see if I can find a vacuum plug line. Also might look into that box under the hood where the vacuum lines go into maybe thats bad? 
I think this problem has happend since I bought it back in Oct of 2010, and before that the truck didnt get used alot so maybe something just froze up without getting used alot.


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## alldayrj

the lines leak, so the pump runs 24/7 and burns out. you're probably going to need a new pump. my buddy found the leak with a vacuum tester and we put the new pump in and everything works great now.


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## mklawnman

Where is the pump located? ON the firewall on the passenger side? How much is something like this to replace?


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## TwiceStroked

Passengers side inner fender, black about the size of a small shoe box.


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## tjctransport

default setting on the ford heater controls is defrost. if nothing works but defrost, you have a vacuum leak.


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## mklawnman

Should I get a vacuum tester and see if it is just a leak in the line? or could it be that the pump is bad? Just wish I could find a diagram of the vacuum lines or something of that nature ha. Are these vacuum lines the same ones that go to the 4x4 system? I know I dont have the locking hubs working anymore, I have to manually turn them to get in 4x4 which isnt a problem, Id rather do that since I know it is in 4x4 mode.


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## dieselss

no you dont need one. its a black box on the pass fender well. just a little bit behind the pass battery. if you turn the truck to "run" you might be able to hear it. maybe not..if you unplug the vac. lines going to it. the pump should run if its working.if not then you need to check for pwr and gnd at the connector. if it runs then you have a problem else where in the system that you need to find.


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## tjctransport

if you have electric shift 4X4 with auto hubs. check the front axle for leaks. that is usually where the vacuum leaks are.

and yes, a vacuum gauge is the only way you are going to find the leak. start at the pump and work your way out. when sooner or later you will loose the vacuum at a line and then you will know it is that line that is bad. 

don't be surprised if you find more than one bad line.


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## plowguy43

My buddy replaced the vacum pump on his 05 Diesel by himself, got it online for $65 I believe. He is not mechanically inclined and was able to do it easily.


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## Drottlawn

I would put my money on the front hubs leaking and causing your issues. My old truck used to do the same thing until I got the front hub seals replaced. Then everything worked as it should including my auto hubs. Didn't realize what I was missing! Very Very common problem on these trucks.


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## mrv8outboard

Here are a few things to try and help. It does sound like your vacuum pump is bad.


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## mklawnman

Well I think its a bad vacuum pump. I checked on my F250 7.3L Diesel and ran the climate controls and the vacuum pump ran for a bit then shut off, and in that truck I am getting air out of the vents and to the floor so that truck is working fine. On my F350 the vacuum pump didnt run at all when I turned the climate controls on.. So I think that is what is wrong. If i get a new pump and my Auto Hubs are still bad my guess is that the pump will wear out since I do have a leak at my hubs. So until I get the hub vacuum lines fixed or get new hubs Ill have to deal with the heater going to defrost default for now.


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## mklawnman

Hey Mrv8outboard I opened those files but I cant scroll on the page.


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## mrv8outboard

OK I will fix it.


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## B&B

mklawnman;1404507 said:


> If i get a new pump and my Auto Hubs are still bad my guess is that the pump will wear out since I do have a leak at my hubs. So until I get the hub vacuum lines fixed or get new hubs Ill have to deal with the heater going to defrost default for now.


 HVAC issues and eventual vacuum pump burn up is very common on these trucks due to leaky hub vacuum. Permanent fix is to plug the lines in the wheel wells with a small ball bearing or BB.


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## stoneexc2

just track the lines from your hubs and cap them off closer to the vacuum pump I had the same problem on my 00 f250 then I just put warn lockouts on for about $125


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## mrv8outboard

I will try again with these PDF's.


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## mklawnman

Thanks mrv8outboard, they now work.
I will also be looking at the vacuum lines as well, not in a big hurry to do all of this work since the heat works in the truck and my 4x4 works manually. And we havent had much of any snow to pay for the parts. But since I have the time now I dont mind working and looking at this stuff now and getting more knowledge of these trucks. These diesels dont seem to be too complicated to work on, but I dont do all the work, just dont trust myself with some of this stuff yet. Getting there tho.


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## shammy

*same problem*

hi peeps ..k I turned my truck key to on and the pump keeps running and never stops.. anyone


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## shammy

mrv8outboard;1404718 said:


> I will try again with these PDF's.


hi would you happen to have some of these for a 2001 f350 diesel 7.3 4x4


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## tjctransport

if the pump keeps running you either have a leak somewhere, or the pump is bad.


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## mcwlandscaping

shammy;1783343 said:


> hi peeps ..k I turned my truck key to on and the pump keeps running and never stops.. anyone


Need more truck details....do you have auto hubs, if so, probably vacuum leak in the vacuuming lines for them....use manual hubs, cap/plug lines and never worry about it again. I personally had a hole in my vacuum chamber. Not typical but clearly possible as it happened. You may have to do this a few times but park in a real quiet place, start your truck, let the pump run for awhile, then shut your truck off and listen for an air leak somewhere. It may help if you have some else on one side of the truck and you on the other.


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## shammy

mcwlandscaping;1783568 said:


> Need more truck details....do you have auto hubs, if so, probably vacuum leak in the vacuuming lines for them....use manual hubs, cap/plug lines and never worry about it again. I personally had a hole in my vacuum chamber. Not typical but clearly possible as it happened. You may have to do this a few times but park in a real quiet place, start your truck, let the pump run for awhile, then shut your truck off and listen for an air leak somewhere. It may help if you have some else on one side of the truck and you on the other.


sorry about that ..yes I have manual hubs. but you would think the shop would cap those off. how do I know which hose to cap off..thanks


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## mcwlandscaping

shammy;1783624 said:


> sorry about that ..yes I have manual hubs. but you would think the shop would cap those off. how do I know which hose to cap off..thanks


Hold on....do you have push button 4*4 or shift on the floor? If you've never had auto hubs, then that's not your problem as there won't be lines, or shouldn't be anyway, to the front axle. However, if you have had auto hubs and then replaced them, check the lines to make sure that they are actually capped off/plugged/etc. Do the easy stuff first, locate the pump and make sure lines are connected and not obviously worn through. Check your reservoir for obvious issues and rest of the truck like I mentioned to listen for leaks.


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