I have a 1999 E150 high top conversion van that I bought a while back and I’ve since been going over it mechanically and also have gutted the interior and am almost done refinishing that (a post for another day). I only have a couple issues left to tackle, one being the rear HVAC.

As a conversion van, this thing has an after market rear unit and is not set up like the factory rear air.

So here are the problems:
The fan control works fine (has a 3speed fan controlled by the factory “rear fan” switch on dash), however it only ever blows ambient air.

I think it blew hot air a couple of winters ago, but after I did a coolant flush it stopped blowing hot. I just now replaced the vacuum controlled heater valve behind and under the driver door since I’ve been told those often get clogged up. While I had the lines disconnected, I flushed the rear heater core. Still no luck.

With the AC on, the high pressure line gets cold at the rear unit, but no cold air. I’m wondering if the thermal expansion valve is stuck shut, not letting the Freon to flow?

Here’s a photo showing the heater valve I replaced (tucked above the heater hoses on the left side) and the AC lines going to the back unit. The AC lines have some sort of valves on them, are these to shut off rear AC? I didn’t want to mess with them just yet.



Here’s the rear unit. You can see the thermal expansion valve on the high pressure AC line and a temp probe that goes inside.
The heater hoses that enter the unit above the AC lines never got warm when I was testing it after replacing the aforementioned valve.


I appreciate any insight on how these units work and any ideas of further troubleshooting. I’m crossing my fingers that I won’t have to open up the AC lines to fix the cold air!

btw, both AC and heat work fine up front on all settings, though I did have to recharge the AC system.

Thank you!

 

I think you have a blend door issue
There is both heat and cold at the unit
Find the vacuum line and you will find the blend door, maybe
Some of them do not have a blend door at all, and you need to shut off the heat up under the hood
Take more photos of the box and we can tell maybe
Look under the hood for screw type shutoff valves on one or both rear heater hoses

 

There is no blend door at the rear unit (unlike the factory unit). This evaporator unit looks like a ProAir 1100 Evaporator from my internet research.

Here’s a screenshot of an exploded view of the rear unit:


It’s rather simple with a sandwiched heater core/AC evaporator, a 3-speed blower, a blower resistor, and a thermal expansion valve. That’s it.

So whether the unit is receiving hot coolant through its heater core or cold AC Freon through the evaporator has to be determined somewhere up front (I’m assuming).

I thought the heater control valve that I replaced would control it, but maybe I’m wrong? Does anyone know where the vacuum line that controls the valve go to? Here’s a better photo of the valve I’m referring to:


Thanks once again!

 

Cool, look for one of those vacuum shutoff valves up front somewhere

 

Well, I have the heat working now. I think there was just an air bubble in the system from when I replaced the heater valve under the van. It now blows hot air out the rear vents when the mode is anything other than AC or off.

Now to get the rear AC to work…
I’m guessing it’s either a stuck or plugged expansion valve but will have to do some more troubleshooting.

 

Rear AC is now also working? What did I do to fix it? Nothing, it just started working one day. Now keep in mind, it does not blow as cold as the front, about 55-60*compared to the front’s 40* when checking with a vent thermometer, but from my research, this is normal.

Only thing I can think of is that I’ve only recently started driving the van a lot, it has been more-or-less parked for the past year. Maybe it needed the more aggressive use to “get the juices flowing” 😂

That leaves me with using the AC all summer and most of the autumn and seeing if it keeps its charge.

 

Hi, I stumbled across this thread, and since it was recent wanted to see if you continued to have everything work? Also wondering if the valve you replace "fixed" the problem, and just took a bit for it to work?

I am having the same issue in my 1999 E-150 Conversion by Elk Auto.

Exact same issue, and I believe we have the same Pro-Air Inc rear HVAC system.

Before I found this thread, I had zeroed in on it being the water valve, or perhaps a failed vacuum line? @woodsnhills

After reading this, thinking I will replace the water valve.... but since the vehicle has been sitting a lot over the last 2 years, maybe I should just drive a bunch and see if it starts working? Welcome thoughts from anyone....

 

Yes, everything is still working. I still believe that the valve needed to be replaced, then the van driven to get any air bubbles out to fix it. Rear heat and AC still working (AC is not the coldest but that’s a design flaw IMHO). Have been using AC almost every time I drive the van and it’s still blowing cold.

My van also has an Elk Auto sticker in the engine bay and an Archer badge on the rear. Probably came from same conversion shop.

 

That's great to hear. I went ahead and replaced the heater control valve... (made a mess with the coolant :-p ) and then drove it around a bit until everything was heated up good. Still no hot or cold air in the back- though it did feel a bit warmer than the outdoor temp. How much did you drive it before it started working?

Anyway - thanks for the reply. Nice to know there is another person with one of these conversions trying to keep it going.
We love ours, and until I parked it (got a new job that has me out of town a lot) the heat and AC were working fine in the back.
Going to take my parents on a little trip and was hoping to get it working again.

Incidentally, we also have the same vacuum leak issue on the front HVAC, and when I get time I will try to one of the youtube repairs to get the vents working again. Love th van- just little things to take care of.

Thanks for the reply- I will keep driving, and hopefully (fingers xed) it will start heating and cooling back there.
How long did you drive before it worked after you changed the valve?

 

I don’t remember exactly but I think it took a few trips to work (about 20 miles of interstate driving plus some city driving) to get it working. I have a feeling the somewhat aggressive acceleration getting up to speed on the interstate helped.

i also love our van. I’ve gutted the interior and am almost done redoing it, but like most projects, it’s the last 3% of work that just seems to drag on. Maybe I’ll do a post on that work some time in the future.

 

I just found this thread - very interesting. Thanks for posting.
FWIW...
We have an '03 Elk (plus RollX) conversion... bought in 2012 with 17k miles. There is a "ProAir" sticker under the hood showing the refrigerant capacity.
The rear heat has never worked since we had it, but the A/C always did.
A friend looked at it and we traced to that vacuum valve - but the valve seems to be working.
We then discovered that the rear heat does blow warm when the master control is set to "defrost".
Our next step was going to be looking behind the radio to see if any vacuum lines were crossed up... but haven't yet gotten to that step just yet.

 

SPAL 010-A70-74D 12v
theyre made by braun and figured this would help alot