I'm bringing back this topic as I am having a Problem with my HVAC selector dial.
I have hot and cold air just can't direct it to areas in the cab.
I have done this so far without success
1. Isolated hubs at the 90* bend of vac. Supply to hubs
2. Have confirmed that pump is running and will shut off when sufficient vacuum is reached
3. I have tested tank for leaks by blocking exit hole of tank and pump stops.
4. Confirmed fuse 28 is good
5. Did the soapy water bubble test
The only thing left I think, is the FWD vacuum selinoid just forward of the pump mounted on the wall. I took it off and inspected it. No obvious breaks or cracks that I can see

The hubs were replaced with manual Warn hubs several years ago and the vacuum hose to each hub are capped off tight. That's whyni took the hose apart at the 90* elbow where the tank is.
Before I go and spend the money on a new FWD selinoid I want to hear from you folks what I'm missing or neeD to check

Perplexed to say the least
Glenn

 

Manual hubs do not need the pulse hub vacuum solenoid. Remove and plug the vac line that goes to it and you should be good to go.

 

Thank you PaysonPSD. that took care of my problem. Put a screw in the end with some silicone. Worked like a charm
Thank you

 

You're welcome. I like the easy ones.

 

I've read this thread, and done some trouble shooting and I have no idea whats going on with my truck. About 3 weeks ago, when I switched my truck to 4x4, I noticed the A/C went blew out the defrost, then down the road a little while it switched back to blowing out the vents. I didn't think to much of it at the time.

So I read this thread, and I went through and checked all hoses and fittings, and I replaced the vac hoses in the wheel wells going to the FWD hubs. These hoses were pretty bad deteriorated, but everything else was ok.

So I started the truck, and turned on the A/C and flipped it to 4x4 high, and the A/C switched from the dash to the defrost vents. So I went over to the reservoir and giggled the hoses coming out of the solenoid, and the A/C went back to the dash vents. When I switch back to 2wd, no change. So I turned off the truck and inspected all the fittings, and didnt notice any bad hoses or fittings. So I pulled the hose off the reservoir and let all the pressure out. Then I went to start the truck again and the pump ran for 40 seconds, then cut off. I started the truck up and turned the a/c on the dash vents, when I switch to 4x4 the a/c went back to the defrost. So I went to the solenoid switch and giggled the hose going to the front hubs, and no change in the a/c. The I giggled the hose going to the A/C system it switched over to the dash vents. Then I did this a few more times. Sometimes the a/c would switch to defrost if I selected 4x4 high and sometimes I would have to go all the way to 4x4 low to get it to switch to defrost, but it would never go back to the dash unless i giggled the hoses. I inspected the hose going to the a/c system and didnt see anything noticeable. Then I pulled off the cover on the Hublock vac solenoid, and the filter membrane crumbled when I tried to pull it out. So a blew out all the parts the crumble and put what was left it back in there.

I'm thinking this is associated with that solenoid, and it looks like Ford has them for $83. I'm not sure if thats really the problem or not. Do yall think this solenoid is the problem or could it be something else that is easier/cheaper to fix? Is there anything I can do to fix the solenoid I have?

Thanks ahead of time.

 

This seems to point to the problem being toward the HVAC system or the vac line that runs to the HVAC and not back toward the vacuum system other then where that HVAC vac line connects to the vac reservoir.

 

I have manual hubs with a 2H, 4H, 4L selector switch on the dash. I did notice tubes going down to the fron t axles.

I thought those tubes were part of the ABS. ...are they really for 4WD? With the manual hubs. aren't they useless.

I dredged up this thread because I have the heat selector switch not working.

We did notice a missing hose on the air-pump. It points straight forward towards the grille.

Is there a pneumatic diagram here somewhere please?

(I replaced the selector actuator down behind the glove box - no change - not surprised - should have come here first)

 

Thanks,
I think I found my answer.....

 

Resurrecting this one more time. I have the same problem. I plugged the lines going to the FWD solenoid and my air works like it should. With the 2001 F350 FWD with manual locking hubs, will my FWD work? My truck is blocked in the driveway right now and can't road test it.

 

you more or less gave your self the answers here, check your hubs, they are known to be problematic and have vac leaks, good chance here they are doing this verry issue on your truck

also isolate the entire system (leave the vac pump hooked to the tank, turn key on (not running) and after letting air into the tank let the pump run and see if it turns off, if it does (usually about 30 seconds of running) then thats a good area, and you can add one more area (lets say esof solinoid) and see if it retains vac, if it starts running and stays running when you add a section that may indicate where your issue is and what area to look in.


Hope this helps!