I have a 5-sided access panel on top of the dash on the passenger side. Its not an air bag, and its quite close to the windshield, so it's in a flat surface area facing up. There appears to be a small detent to access it with a pry, but I've not done that yet for fear of gouging it up. Is it to get at HVAC stuff or ? Thanks for any help...I ask this because I'm trying to figure out why my HVAC has defaulted to defrost, no matter what the selector is on (and no, its not the fault of the resistor block, which apparently is typically the cause).

 

if it has defaulted to defrost you may have a vacuum problem. i know your not 4x4 but you are diesel! anyways when the 4x4 diesel guys engage the front wheel drive and the HVAC defaults to defrost it usually means a vacuum leak at the hubs, but in your case its possibly a leak in the dash somewhere.

i new to the vans, so i cant help ya with whats behind the panel...

 

It is to access some of the Vacuum lines for the heater controls ...and it is real easy to take out....But since you have the Diesel I would check the Vacuum Pump first and then I would look at the main manifold Tee ( on my 7.3 it is close to the Booster ) and connections to it first....Most times it is the Pump (I have the belt driven one...you might have an electric one I don't know ...) I would start there

 

Thanks guys. Yes, the access panel came off easily and the vacuum parts are easily accessible in there. Lotsa little vacuum lines running to the dash switch from there. Everything looks new, and I think my issue is with the fan speed selector side not the output/vacuum controlled switch, but will report back to you when I do more digging.

 

If it defaulted to defrost, it is almost definitely a vacuum problem. Remove the panel and disconnect the black vacuum hose (that comes from passenger side under dash) and check for vacuum with engine running. Vacuum operates the flapper, not electric. That's where I'd start the search. If your vacuum pump has failed, your brake low vacuum warning light will come on. If the leak is in the hvac vacuum line, it won't be enough to effect your brakes.

 

the 6.0 diesel should have hydroboost for the brakes..... diesels dont really make vacuum like the gas engines do. that is why they have a vacuum pump.

his signature stated a 6.0 so i am baseing my assumptions from that

 

I can't see any signature or year, make, model, engine, etc. It always helps to include those details in the original post though. Regardless of whether or not it has hydroboost, the blend door actuator, and the entire vacuum system, is the same on all of the vans. The blend door actuator operates off of vacuum. The most common problem causing it do default to defrost is a dry cracked vacuum hose or connection in hose to reservoir or reservoir to dash. The diesels do not need the reservoir since they don't rely on engine vacuum like gassers. I just ran a new silicone hose from dash directly to vacuum splitter under hood and all works great again. The reservoirs are there because most vans are gas, Ford could just install one system on all, and gas engines don't supply enough vacuum on start-up to operate vacuum accessories without a reservoir. The other possible problem is that operation of the blend door could be blocked by debris. You can check for that by sticking your head under passenger dash (in front of where passenger's feet would be) and check for blockage. With no vacuum pressure, the blend door automatically defaults to dash (defrost) vents.

 

I guess I should have announced I highjacked the thread (sorta) and wasn't the OP. My signature block always shows make/model/year/engine.


Anyway, after pulling and pushing on all electrical and vacuum lines and fiddling with the resistor block a little, all appears to be back to working order. I don't really know what was amiss for awhile, but I gave it good look see today, as well as under the top-of-dash access panel showing the two vacuum operated diverters, and those worked well, along with speed selector switch and function switch. So, touch wood, I'm good to go...Thanks for all the tips and I did learn a lot about how the HVAC works, which is always useful

 

Sorry, disregard the first line of the last post...this WAS my thread (I meant this particular reply for the 6.0 powerstroke section)....but the conclusion is the same...all is working well!

 

Signature block doesn't show on the mobile web site version.

I once sassed a Moderator due to this.