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Old 04-06-2021, 01:43 PM   #1
Join Date: Nov 2020
Posts: 25
Anatomy of AC, dual units, and conversion help


Trying to get a more solid grasp on the HVAC system on my bus, help would be greatly appreciated. I've read dozens and dozens of threads, scattered about the internet. This thread is an attempt to get some clarity for the average user with pictures.

Bus: 1999 Ford E350 Cutaway, 7.3l diesel motor, SRW (single rear wheel, as opposed to a dually), converted by Girardin, 4 window.

-there is a dash AC unit, I dont know if it works independent of the rear AC.
-there is a rear, ceiling mounted AC unit (Carrier, R134A, evaporator and blower).
-there is a side-skirt with 2 fans over a condenser, with what I believe is a dryer.
-there are two lines from the engine compartment to an auxiliary heater in the back of the bus, those two lines have a ball valve to isolate the rear heater.
-there are three radiators, one large (engine), one medium (?), one small (?)

-does the van have a stock compressor? guessing yes
-are there one compressor or two? guessing one
-can I run the dash AC independent of the rear? guessing no, as there is a t-fitting after the condenser coil that runs a line to the front and the rear of the bus.

I have removed the rear AC evap and blower unit (lines are still in place), how would I go about getting the dash AC to work? I see the t-fitting that is after the condenser on the chilled line, however the hot line appears to only run up to the engine compartment. Would it be as simple as changing the t-fitting to an elbow fitting to isolate the front from the rear, and then capping the hot line that is running to the rear from the front?

I understand the benefits of an on-road AC unit. However, the cost on space is too high for my application that I use the bus for 75% of the time. I have another thread started about having a quick-disconnect AC system for the rear, or recommendations for a lower-profile evap/blower.

I've numbered each of the pictures so that we can all stay on the same page when discussing different parts.
Attached Images
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Manchild is offline   Reply With Quote
Old 04-06-2021, 01:46 PM   #2
Join Date: Nov 2020
Posts: 25
Here are the rest of the pics
Attached Images
File Type: jpg IMG_7379.jpg (282.1 KB, 2 views)
File Type: jpg IMG_7382.jpg (229.7 KB, 3 views)
File Type: jpg IMG_7384.jpg (245.0 KB, 3 views)
Manchild is offline   Reply With Quote
Old 04-06-2021, 02:24 PM   #3
Bus Geek
Join Date: May 2009
Location: Columbus Ohio
Posts: 15,604
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
this is correct.. there will be a sercond T underneath at the condenser like shown. there is only one hot gas line since the condenser is shared.. on this type of system there is no second condenser up by the engine radiator.. on a bus you will almost always have a transmission cooler and sometimes if your brakes are hydroboost there is a powered steering cooler.. engine oil usually doesnt have an external cooler on a 7.3 (ive rarely seen one but it is possible).. so thats why you only have one gas line going from the compressor to the condenser.

if you do not need the under-bus space you can remove the 'T fittings for the rear and pipe directly to and from the dashboard evaporator only and have the dash air using the under-skirt condenser.. if you need that space then you'll have a lot more piping and work to do installing a van condenser in front of the radiator..
cadillackid is offline   Reply With Quote
Old 04-06-2021, 04:08 PM   #4
Join Date: Nov 2020
Posts: 25
Thank you good sir. If I understand correctly, there will be two T-fittings then? One next to the condenser on the side skirt and another in the engine compartment?

If there are two, and I replace the T’s with Elbows in the right configuration then I can run the dash unit using the skirt condenser correct?
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