Newbie, installing "custom" system

[bohica2xo]

The elevation of the rear evaporator should not be a big deal. There were GM Suburbans with a big evaporator mounted in the center of the headliner.

Yes, avoid traps in the suction lines. Condensers can be mounted much lower than the rest of the system. Many Isuzu COE trucks mount the condenser under the truck, about a foot off the ground.

Filling a large unknown system can be a challenge. But you are using mostly known components. The original H1 evaporators and condensers have a factory specified charge level for oil and refrigerant. Sounds like you are relocating one of the evaporators vertically. So you may be adding a few feet of suction line, which is not a lot of refrigerant.

The old R4 likes a bit of oil in circulation, the OCR for the R4 was generous. Do you have the charge specs for the H1 system you are using?

[Mogman]

Yes the basic system I am using is for the M1151A1 it is 3lb 8oz of R134A and of course the original oil was PASG150 but have not found the amount yet.

[Mogman]

Also the original electrical portion of this system is a complete nightmare in typical military fashion but did not even have a thermostat.
I planed on using a much simpler approach with a trinary switch and adding a thermostat with the bulb in the front evap's intake stream.
There will be a mix of 12V and 24V components but I need relays for the evap and condenser fans anyway so that will be easy enough, my truck has a dual voltage system with dual alternators.
I also planned on using two dryer/filters because of the split liquid streams it seems easy enough and would give me more drying ability.
If any of this sounds off let me know.

[Mogman]

The "system" will run WOT most of the time, a Humvee has terrible insulation and is about as air tight as a barbed wire fence.
And I live in S TX!!

[bohica2xo]

OK, to put this in perspective, your OEM system would have been 56 ounces of refrigerant and unspecified oil. Are you sure this is the dual system spec?

A 1990 Suburban for comparison:
W/O rear air 52 ounces of R12 & 8 ounces of oil
WITH rear air 84 ounces of R12 & 11 ounces of oil

Moving up to the 1996 - 2000 Suburban with 134A:
W/O rear air 36 ounces of 134a & 8 ounces of oil
WITH rear air 64 ounces of 134a & 11 ounces of oil

During the span of '96 to 00 GM went from the R4 to the Denso compressor. The charge weights and oil ounces did not change, the only difference was from PAG150 to PAG 46.

So there is no difference for your compressor swap other than oil weight, and the additional plumbing volume.

[Mogman]

I will double check, I got the amount from a forum it specified
Freon charge, fl oz, for
2 man, front only: R134a, 1 lb 7 Oz (0.65 kg)
4 man, front and rear: R134a, 3 lb 8 Oz (1.59 kg)

This seems a little light especially for the 2 man.

[Mogman]

The condensers are in the rear fenders, one each side so that is allot of hose/lines

[Mogman]

I was able to confirm, and found the original wiring diag. does not look that bad in schematic form but the harnesses are bulky with a ton of connectors in them.

[bohica2xo]

Wow. Run an R4 compressor, then put a crap system in for the grunts. Typical .gov contract decision.

I don't know what the OE front evaporator looks like, but you might want a bigger one in the back. Got any pictures of this equipment?

[Mogman]

Here are the condensers one in each rear fender, with the hard lines that go between them, the condensers are up right, one does not have fans, there is only one closeout shown that goes under the condenser but is actually upside down, and a picture of the grill on the outside of the fender not.
I will find the rest