Want to put A/C in a M925A1... anyone got pictures of their install?

[74M35A2]

Maybe that is what I should do instead of replacing my broken back window glass...

 

[grendel]

Maybe that is what I should do instead of replacing my broken back window glass...

PLease do.

 

[simp5782]

Maybe that is what I should do instead of replacing my broken back window glass...

Guy said cooling is 36,000btu and 48,000btu heat. Should be good for up north.

Sent from my SM-G935P using Tapatalk

 

[simp5782]

Finished the install. My mobile hose making guy will be out tomorrow to run my hoses. Should be blowing cold tomorrow night. That is the bracket I made that is listed in the classifieds.

 

[simp5782]

Got my lines ran today. Pulled a vacuum on it. Charged with 3.75lbs and it is still showing a little low. 150 on the high side and 30 on the low side at idle. Dropping to 18 @ 2000rpms. Idle temp at the vent it is blowing 60 degrees. Road temp just around town is 50 degrees out of the vent.

Used a total of 33 feet of AC line along with all the fittings crimped and ran was $325.00
AC/Heater Box Combo # 13-4506 was $330 shipped
MRAP Mobile Climate Control Condenser/Fan Unit Part number 14-4004. $150 shipped - They are sold on ebay.
4311 Compressor found on ebay for $110 shipped. NEW - not a reman unit.
Bracket I made myself for the engine
Misc bolts and metal $50
4lbs of Freon $30

So I don't have too much into it for ice cold air.

I have attached the wiring diagram for the condenser fan unit provided by MCC.
Pin A - 24 volts all the time
Pin B - Connects to pin C
Pin C - Connects to pin B
Pin D - Signal wire from switch on dash or unit
Pin F - Ground

Run wire from compressor to the Black wire off of a fan motor that is HOT when the relay switch/Pressure switch for the system is on it will engage the compressor.

On the AC /Heater unit box Orange is 24 volts, Black is ground, White is to Pressure Switch, Blue is nothing.

https://youtu.be/69OfiBbPk6w

 

[jonesal]

I'm impressed with your work. Your homemade brackets look like they turned out well. However, do you consider 50 degrees ice cold air? That system should easily get lower than that depending on ambient air temperature. If you're running R134A, those head pressures seem way low. I see it's 88 in Memphis today so your delta is 38. Is that what your AC person said was ok? I've built systems (using similar components) that will blow lower than 40 at 90 ambient. So when it's 100 there, your vent will be somewhere around 60 moving and 70 idling? Is that ok with you?

I'm just about to start mounting my AC bits on my M923. I'm using the kit for the M916A2 or A3 (I can't remember which) and it doesn't have fans on the condenser. I'll report back to see if I get it to blow colder.

Enjoy the cooler air!

Al Jones
M923
Brookings, SD

 

[simp5782]

I'm impressed with your work. Your homemade brackets look like they turned out well. However, do you consider 50 degrees ice cold air? That system should easily get lower than that depending on ambient air temperature. If you're running R134A, those head pressures seem way low. I see it's 88 in Memphis today so your delta is 38. Is that what your AC person said was ok? I've built systems (using similar components) that will blow lower than 40 at 90 ambient. So when it's 100 there, your vent will be somewhere around 60 moving and 70 idling? Is that ok with you?

I'm just about to start mounting my AC bits on my M923. I'm using the kit for the M916A2 or A3 (I can't remember which) and it doesn't have fans on the condenser. I'll report back to see if I get it to blow colder.

Enjoy the cooler air!

Al Jones
M923
Brookings, SD

Most cars wont blow below 55 or so. Optimum pressures should be 170/30. dropping to 18 at 2,000rpms. At 10 it could start to freeze up. . The evaporator is 42 degrees at its core and the expansion valve is at 52. The pressures also indicate that the system is undercharged so it could get colder. But. 30 to 45 degree difference between outside and inside is Alot in the southern heat

Sent from my SM-G935P using Tapatalk

 

[74M35A2]

High side of R-134a should be 2.2-2.5 times ambient temp. Duct outlet should be near 39F. Low side 25-40psi.

 

[simp5782]

High side of R-134a should be 2.2-2.5 times ambient temp. Duct outlet should be near 39F. Low side 25-40psi.

I had the pressures backwards when i typed it. Dyslexia kicked in. I was parked in the shade when i charged it as well

Sent from my SM-G935P using Tapatalk

 

[simp5782]

Chart


Sent from my SM-G935P using Tapatalk

 

[74M35A2]

Yep, chart will work. Condenser have fan running?

 

[simp5782]

Yep, chart will work. Condenser have fan running?

Compressor wont come on unless the fans are on. I will mess with it tomorrow.

Sent from my SM-G935P using Tapatalk

 

[winfred]

i find the best way to find a custom charge is get the system running with all of the air flow you can get across the condenser and engine around operating speed (for a gas car with a hydraulic fan clutch id say 2k if the clutch will stay locked up at that speed, not sure with your remote condenser set up but maybe 1500) and let the vent temps drop as low as they will get and trickle in a little bit of freon and watch the vent temps, once they stabilize repeat, eventually you will reach a point where the vent temp levels off and more freon drives it up. sweating and really cold return side line from evap to compressor is good sign, freezing return line not so much, you need enough freon in the evaporator to properly saturate it and enough liquid coming from the condenser to maintain it without overloading the expansion valve, the huge condenser may make it interesting. a refrigeration system works much like the cooling system on the engine and needs enough liquid to transfer the heat, gas doesn't transfer heat well. i saw those triple fan condensers and wondered how they would work for my deuce ac plans, biggest thought was the 3 fans plus interior blower would likely overload the old school charging system

 

[simp5782]

I wonder if the three condenser fans plus the two radiator fans plus the blower unit will overload Clint's alternator.

 

[74M35A2]

You're running a 100 amp Delco brushless unit. The brushless units can be weaker at idle than a brush unit, but they are made to last 1 million miles. Don't be surprised if it dips out of the green at idle with all of that on, depends greatly on your idle speed.

 

[Buffalobwana]

Compressor wont come on unless the fans are on. I will mess with it tomorrow.

Wes,

two things for you.

I dont know your setup. So I'll use mine as an example. The Red Dot units made for hummers keep the compressor on all the time. Yeah, sounded odd to me too, but after a year, it's ice cold. Still works.

The pressure ports on the evap/dryer dictate at what pressure the fans kick in and when they turn off. I don't remember what the pressures are though. Yours may or may not have pressure ports there. Do they have pressure ports anywhere? Or are fans run on temperature of coolant?

I left My gauges hooked up for a day while i drove around. Give it a shot if it's mechanically possible. I drove dallas to Texarcana with mine hooked up. See the pressures in the morning and in mid day heat. Then you will have a good idea.

oddly enough, while driving, it took the fans longer to cool the condensor. There must be natural opposite airflow coming from the top down. I should consider if it's possible to reverse my fan direction.

edit: my condensor is mounted on top of my toolbox, passenger side, facing up and out at an angle.

 

[simp5782]

Wes,

two things for you.

I dont know your setup. So I'll use mine as an example. The Red Dot units made for hummers keep the compressor on all the time. Yeah, sounded odd to me too, but after a year, it's ice cold. Still works.

The pressure ports on the evap/dryer dictate at what pressure the fans kick in and when they turn off. I don't remember what the pressures are though. Yours may or may not have pressure ports there. Do they have pressure ports anywhere? Or are fans run on temperature of coolant?

I left My gauges hooked up for a day while i drove around. Give it a shot if it's mechanically possible. I drove dallas to Texarcana with mine hooked up. See the pressures in the morning and in mid day heat. Then you will have a good idea.

oddly enough, while driving, it took the fans longer to cool the condensor. There must be natural opposite airflow coming from the top down. I should consider if it's possible to reverse my fan direction.

There is no point for the compressor to be on all the time especially if the system isnt on. Your compressor has to run thru the pressure switch somehow. Mine just jumps a power wire to engage the single wire compressor rather than having to run another inline fuse to protect it. The fans and the relay are wired into the pressure switch on the dryer. . Fans go off. Compressor goes off. My system is overkill for the cab but general complaint in the summer time is that the red dot units have a hard time keeping the cab cool on a solid steel cab. Mine on low at 95 outside will give you chills. It doesn't have to work hard at all.

Sent from my SM-G935P using Tapatalk

 

[Buffalobwana]

My compressor isn't on, unless the AC is on. As for being on all the time AC is running, That's Red Dot's design, not mine. (There is a chance I'm wrong here.) I might want to run a meter on it and see if I'm wrong.

Usually, you should hear it cycle on/off at idle, but I don't hear it go on and off. So I assume it's on all the time and the pressure switches manage the fans that manage the pressures.

I dont know about all other AC systems. I don't know your system, which is why I asked. Mine has blown air in the high 30's on a 75 degree morning. It has no trouble keeping my cab cool. It even worked pretty dang well with the soft top on!

 

[74M35A2]

There should be a pressure switch on the low side of the system. This switch has 2-3 functions:

1. Prevents compressor from engaging if low side pressure is too low. This assumes the evaporator is ice blocked, or system too low on charge for safe operation.
2. Cycles compressor on/off if cabin blower fan air across evaporator is on low and not pulling enough cold out of the system (high pressure on low side).
3. Cycles the compressor off if the upper safety pressure is achieved, say for example 410psi. This is just an example pressure. This sensor is typically on the high side of the system.

Low side of the system may form ice on the lines if the system is low on charge.

A/C clutch signal request originates at the A/C control panel when the A/C button is turned on. Circuit feed then goes through the low side pressure switch to determine if A/C compressor operation is permitted or not, based on low side system pressure.

Really simplistic systems run the condenser fan(s) continuously. Step up from there is to run the condenser fans whenever the compressor cycles on/off. Advanced systems use a pressure sensor to run the condenser fans on an as-needed basis, completely separate of the compressor clutch signal (and PWM vary the required speed of them also).

 

[Buffalobwana]

Advanced systems use a pressure sensor to run the condenser fans on an as-needed basis, completely separate of the compressor clutch signal.

I am fairly certain that is what the Red Dot Hummer system does. While I do not remember the numbers, it comes on at exactly 400, for example and off at 250, again, for example. Every time. No difference in any other variables. Rpm, outside temp, etc.

Now i am curious. I am going to run a meter on my compressor wire. It is the black wire with white stripe that goes into the evaporator unit. Mine has a small pinhole in it where I tested it before.

Id like to know if my compressor does, in fact, run continuously, as I suspected, or not ... and why.