Red Dot R-9777 Install on M939A2

[74M35A2]

Just scored a decent deal ($500) on a 24V Red Dot R-9777 A/C unit, which has 25,000BTU of cooling capacity. Been wanting a rooftop unit to keep cab space open and 3 passenger ability, let alone rear window usage. It is only 8" tall, and comes dark grey. Unit contains evaporator, condenser, fans, all pressure switches, and the dryer. Keeps the radiator front clear for a charge cooler later.

Is slightly longer than the roof itself, so I am considering to spin it 180 and mount it to overhang the rear by a few inches. Red Dot recommends a Sanden Flex-7 compressor for this.

Anybody here done an install on this unit? Saw a thread titled almost same as this one, but it went nowhere. Should not look too bad up there, I'll just say it is radar.

 

[74M35A2]

Pre-install pic. Cutting 2 rectangular holes in the cab roof in the next few weeks, along with the 4 required mounting bolt holes.

 

[turnkey]

Nice score...looks great..

 

[Artisan]

I think you have to cut 2 support members clean out of the way
to install that unit. What does it weigh, 80 or so pounds? I think
it would look fine overhanging the front...

I sent a PM

 

[74M35A2]

I think you have to cut 2 support members clean out of the way
to install that unit. What does it weigh, 80 or so pounds? I think
it would look fine overhanging the front...

I sent a PM

Book says 65lbs, but it is less. I'm going to toss it up on the roof and see what happens. If the roof needs support, I will likely seam seal a 1/4" plate of steel under the A/C unit to keep the roof from "oil-canning". May be able to use 2 pieces of low profile Unistrut on the inside to do the same spanning fore-aft connecting the mounting bolts.

 

[74M35A2]

More pics for those considering as I have received some questions and interest. This actual model is R-9777-1-24, which is a 24V cooling only model. You can get it in 12V also, with or without a heater core. I did not want the heat option, so this was a perfect score. Actual weight of this cab rooftop as measured on our certified shipping scale is 47.5lbs. Condenser fins are tough, they don't fold over when touched. You could drag a center punch under its own weight across them with no damage, it would just play a tune. Housing contains evaporator, 2 blower fans, condenser, condenser fan, receiver/dryer, relays (for fans and compressor clutch), hi/lo compressor clutch pressure switch, thermostat, and will drain condensate at up to 15 degree up or down angle. Just mount your compressor and connect with hoses and power. The duct outlet vents do swivel as well, you need to pull them down and then rotate them. Not as easily as todays cars, but they would hold their position better after doing so.

Mod: Unsure how to delete the errant attachment, only shows options to add attachment under attachment management tab, I'm probably missing something.

 

[ke5eua]

Nice. What are you using to mount the compressor to the engine?

 

[74M35A2]

Nice. What are you using to mount the compressor to the engine?

I purchased the proper Kenway/Red Dot kit to mount an ear style Sanden compressor onto the 8.3 engine with military accessory drive (A/C compressor mounts on driver side by power steering pump), but now I am switching gears and have purchased the civilian 8.3 A/C compressor and alternator bracket which combines a more modern 4 bolt pad mount alternator and pad mount A/C compressor all on the serpentine belt with the factory spring tensioner, it mounts the A/C compressor just above the alternator all on the passenger side of the engine. I just need to put this new bracket on and confirm all lines up. I also grabbed a 24V 140 amp pad mount alternator to support the A/C blowing on high while at engine idle (Leece NeVille was dumping new product at a local scrap yard recently when they were moving locations, I grabbed a ton of new stuff for $0.50/lb). Should be an upgrade all the way around, although not cheap. The alternator was $5, but the bracket was $348 new from Cummins. A/C compressor $200-$400 range for new. If I would not have got the deal I did on the newer style alternator, I would not have made this change in direction, as the cheapest I have found a 24V pad mount alternator is $220, which is a 70 amp Chinese clone of a Delco unit that sells for about $450.

 

[86m1028]

Please keep posting pics & progress.

 

[74M35A2]

I will. I have questions into Red Dot about roof cut-outs and sealing before I go tearing into the ceiling of my truck. Here is the civilian 6CTA8.3 bracket with accessories on it as mentioned above:

 

[ke5eua]

I purchased the proper Kenway/Red Dot kit to mount an ear style Sanden compressor onto the 8.3 engine with military accessory drive (A/C compressor mounts on driver side by power steering pump), but now I am switching gears and have purchased the civilian 8.3 A/C compressor and alternator bracket which combines a more modern 4 bolt pad mount alternator and pad mount A/C compressor all on the serpentine belt with the factory spring tensioner, it mounts the A/C compressor just above the alternator all on the passenger side of the engine. I just need to put this new bracket on and confirm all lines up. I also grabbed a 24V 140 amp pad mount alternator to support the A/C blowing on high while at engine idle (Leece NeVille was dumping new product at a local scrap yard recently when they were moving locations, I grabbed a ton of new stuff for $0.50/lb). Should be an upgrade all the way around, although not cheap. The alternator was $5, but the bracket was $348 new from Cummins. A/C compressor $200-$400 range for new. If I would not have got the deal I did on the newer style alternator, I would not have made this change in direction, as the cheapest I have found a 24V pad mount alternator is $220, which is a 70 amp Chinese clone of a Delco unit that sells for about $450.

Ok, I thought you had the nhc250.

 

[74M35A2]

Nope, 8.3 for the win. Turbo power!

 

[NOLATAC]

Any updates?

 

[RobertoGatos]

Whats the part number for that alt. / AC bracket?

 

[74M35A2]

No updates guys, sorry, my business has been booming so I have not had time to play.

 

[Mike929]

No worries.

Looking forward to updates when you get back to this project.