LMTV Air Conditioner AC Main Unit Gen1 and Gen2 Details

[coachgeo]

Exactly right!

???? consider quoting whom/what one is referring too.

 

[Dave21]

[FONT=&quot]Hi Overdrive,[/FONT]
[FONT=&quot] I'm just finishing up the install on a Gen 2 AC kit built in 2009 . Thanks for the great information on your post it made the install a lot easier .[/FONT]
[FONT=&quot] I'm wondering if you know how much Freon does the system take ?[/FONT]
[FONT=&quot] Thanks again for your grace post.[/FONT]
[FONT=&quot]Dave V[/FONT]

 

[m-35tom]

Fuses melt by wattage. This heats and melts the fusible link because it cannot dissipate more than a certain amount of wattage. You are right about the rest...

fuses melt by amperage, wattage has nothing to do with it.

 

[m-35tom]

on a 06 A1R, where is the 24 v supply that the 2 wire plug goes to? that is the orange and black wires.
I have the evaporator coil from a MRAP which is rated 33,070 BTU, the gen 2 is just a little larger so I would assume at least that rating.
Thanks, Tom

 

[Dave21]

[FONT=&quot] If my memory serves me the two wires in the plug one is 24 volts and the other one is 12 volts . [/FONT]
[FONT=&quot]( not switched power is on all the time ) on the lmtv Gen 2 air conditioner only uses the 24 volt wire . This seems to power the servos that regulates the Heat , air Direction servos, AC compressor clutch and condenser fan motors . The original truck wiring harness provides 12 volts for the evaporator fan and panel lights .[/FONT]
[FONT=&quot] Hope this info helps! [/FONT]

 

[m-35tom]

thanks and please change your font to white, black is almost impossible to read.
Sorry that does not help, and that info is not correct anyway. The 2 pin plug is just 24 volt and ground. The 4 pin plug is 12 volt illumination and 24 volt for the blower and 2 ground wires. I need to know where in the PDP the 2 pin, orange and black gets the 24 volt for the compressor and condenser.
I would have almost thought the A1R would already have a connector since it is the only model meant for A/C.
Tom

 

[VehiCROS]

Stupid question, In addition to installing the "Box" does a AC compressor and condenser also need to be installed?

 

[coachgeo]

Stupid question, In addition to installing the "Box" does a AC compressor and condenser also need to be installed?

yup

 

[Ned81]

Old thread I know but I am having an issue with my ac I can’t figure out.
Everything was working last summer. Now my condenser fans aren’t turning on. Is there supposed to be 24v feeding into the high pressure switch on the dryer? That’s where the purple from the 4pin goes. Then out of the switch to the condenser fan. I’m getting 24 in but not out. If it’s hooked up right I guess I have a bad switch?
Thanks.


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[m-35tom]

No, there is not 24 volts fed to the high pressure switch but if the ground circuit is open you will measure 24 volts there. It controls the fan relay which turns the fan on. It is grounded through the fording switch.

 

[Dave21]

Starting a new thread to have this info easily available. I will be updating this post with pictures and other information scattered throughout this forum. Some info and pics were gathered from others who are on the quest for a cooler cab. As I add pictures I will probably group these details in a more logical order so for now just listing what I know.

View attachment 628941 View attachment 628943 View attachment 628944

1. Gen1 and Gen2 AC units have different wiring and how they operate.

2. Gen1 and Gen2 units are also physically different sizes both height and depth however they both slide easily into the stock heater slot on the LMTV.

3. Gen1 units use similar cables to operate the vent, defrost, heat functions just like the stock heaters except they have rotary knobs instead of the pull knobs for the cables. So Gen1 uses just the stock heater 12v/24v power cable.

4. The best way to summarize the two is that Gen1 is mechanical like the stock heater and Gen2 is electronic.

5. Gen1 uses a mechanical fresh air vent door the same as the stock heater in front of the radiator behind the grill. Gen 2 has a door that is internal to the unit so the opening for the fresh air vent is covered by a mesh filter to prevent debris clogging up the door.

6. Gen2 units also use the stock heater power for fan and lights. The fan is 24v and the dash lights are 12v. The factory plug provides both 12 and 24v. MOD: I tapped the 12V dash light power wire on the Gen2 unit to provide dash light power to my aux switch box.

7. Gen2 requires an additional 24v power source to operate the various controls, vent, defrost, etc. They use electrical actuators and WILL NOT FUNCTION if you just have the stock power plugged in. You will only have fan and dash light control. The power plugs are standard SURE SEAL 2 contact connectors and are the same male end plugs that match the female end plugs to the aux 24v power wires under the power distro panel. You will need to either cut the ends off the connectors for the additional power or find those SURE SEAL ones to make an extension wire that goes from the power panel to the 2nd power plug on the Gen2. I am in the process of wiring this item up.

8. The additional power wire needed for Gen2 also sends power to the condenser fans and compressor.

9. Gen1 and Gen2 have the same wire harnesses for all the other components. They are condenser fans, compressor, high pressure switch, and radiator fan cut out signal. This last one is so that when you are fording and flip off the cooling fan using the main dash switch it disables the condenser fans as well.

10. The stock condenser that has the wire harness on it connects to ALL the appropriate connectors on both the Gen1 and Gen2 units (electrical).

11. I claim full credit for labeling the different AC units Gen1 and Gen2

12. There are some one-off variants of Gen1 and Gen2 out there specifically Gen2 units that to me look like prototypes or early production models that are difficult to install due to side assembly bolts that interfere with sliding the units down into the stock heater location. The ones I have seen like this are tan in color. I don't know if we would call these Gen3 units or more likely Gen2 prototypes.

13. Both Gen1 and Gen2 units require weep holes to be drilled into the cab floor for the evaporator condensation drain. Gen 1 units typically have hard plastic drains that stick out below the unit and Gen2 uses 4 duck bill rubber drains with two along side the fresh air door and two more in similar positions as Gen1.

14. Gen1 and Gen2 evap condensation drain ports are in different locations so if you install a Gen1 and then switch to a Gen2 you will more than likely have to drill two additional holes into the floor of your cab.

15. The holes you need to drill into your cab for evap drains are DIRECTLY above the Charge Air Cooler with about 2 inches of clearance. When you drill these holes you have your cab down and must be VERY careful using your hole saw.

16. Gen2 units have a different physical space and cover for your Park/Trailer valve. They require you to switch over to the single Haldex integrated Park/Trailer valve (see my write-up on how to do this). Due to the additional electrical actuators there is less room behind the valve than in stock or Gen1 units so the two valve stock setup would be difficult to retrofit. The cover hole for the valve and mounting screws are designed for the combined Haldex valve and have a perfect fit.

Pic of wire harness for Gen2. Gen1 is the same minus the 2pin round connector for the additional 24v power (actuators and fans). Gen1 takes all its power from the heater power for the stock connector.
View attachment 628940
17. Pin outs for the 4 pin connector from the main AC unit Gen2 to the condenser (not sure if Gen1 wires are the same colors but I will verify tomorrow) Evaporator side colors:
Black goes to fan ground
Yellow goes to high pressure switch
Green goes to compressor clutch
Purple condenser fan power

18. Stock Condenser Wiring:
Here is a pic of the wire harness ends showing the two, two wire connectors for low pressure and high pressure switches and the single plug for the compressor.
View attachment 629925
(Wire identification and operation: Keith_J - "The white two pin plug w black wires is the low pressure cutout switch. The red two pin plug with purple wires is the high pressure fan switch. How this works? Low pressure prevents operation if refrigerant charge is low or absent. This prevents oil starvation in comp. Also, it prevents evaporator icing since temp corresponds to pressure.
High pressure switch makes fans turn on only when needed. Ram air at 58 MPH is more than needed so fans freewheeling)."



Live long and prosper (Spock)

OD

On a GEN 2 would you happen to know how many ounces of refrigerant the system takes?

 

[Ned81]

No, there is not 24 volts fed to the high pressure switch but if the ground circuit is open you will measure 24 volts there. It controls the fan relay which turns the fan on. It is grounded through the fording switch.

This is a gen 2 btw.
Unfortunately I did not install it myself but now I’m trying to fix it. Everything works except the condenser fans and they worked when it was first installed. I’m thinking something came loose since everything was “new” and it’s only been installed for about 8 months. I’m not sure how long the fans worked because it still cools just not very well and the pressure goes way up.
Here is how it’s currently hooked up

The 2 pin plug is connected to 24v and ground in the fuse box.

The single pin plug goes to ground

On the 4 pin connector

Purple goes into the other switch on the dryer then out of that switch to the condenser fans.
Green Goes to the compressor

Black goes to one to one side of dryer switch
Yellow. ( changes to blue at plug) goes to the other side of the same switch.

I’m showing 24v on the purple wire


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[GeneralDisorder]

On a GEN 2 would you happen to know how many ounces of refrigerant the system takes?

If you have the full gen 2 system with the military condenser, etc - the official capacity is 4 pounds (64 Ounces). I was advised by an experienced Motorpool vet that 3.5 lbs is usually where they find they work well.

 

[Ned81]

I did some more checking today. If I jump the plug on the dryer that has 2 purple wires the fans turn on. Bad pressure switch?


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[GeneralDisorder]

I did some more checking today. If I jump the plug on the dryer that has 2 purple wires the fans turn on. Bad pressure switch?


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Sounds like it. Whoever wired it might have wired the fan current through the switch and it's probably not rated to handle it. This burnt out the contacts in the switch. A possibility you should investigate anyway.

 

[Ned81]

Sounds like it. Whoever wired it might have wired the fan current through the switch and it's probably not rated to handle it. This burnt out the contacts in the switch. A possibility you should investigate anyway.

I was thinking take too but I traced all the wires and except for the fording switch wire, everything seems correct. The fording wire is direct to ground. Im baffled on this one.
Another confusing thing is the wire on the plug going to the pressure switch are purple. Same as the power source for the condenser fan.


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[DTinNC]

Old thread I know but I am having an issue with my ac I can’t figure out.
Everything was working last summer. Now my condenser fans aren’t turning on. Is there supposed to be 24v feeding into the high pressure switch on the dryer? That’s where the purple from the 4pin goes. Then out of the switch to the condenser fan. I’m getting 24 in but not out. If it’s hooked up right I guess I have a bad switch?
Thanks.


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I'm still in the process of installing my Gen2... But can you confirm that the system has enough refrigerant? That pressure switch may need to reach pressure before it will close and thereby engage the condenser fans. If your refrigerant is low it may not be building enough pressure. If refrigerant levels are sufficient then it could be a faulty switch.

 

[DTinNC]

On a GEN 2 would you happen to know how many ounces of refrigerant the system takes?

Unfortunately I am in the same situation when I will charge my system (still installing) Refrigerant amount will actually vary based on components and hose lengths. The best way is to use real gauges and watch pressures and temp to tweak.

 

[GeneralDisorder]

Unfortunately I am in the same situation when I will charge my system (still installing) Refrigerant amount will actually vary based on components and hose lengths. The best way is to use real gauges and watch pressures and temp to tweak.

It seems (based on forum posts and youtube videos) that a not insignificant number of installations are using some aftermarket repurposed automotive style condenser core - usually these are like 1/2" to 1" thick and have VERY tiny flat tube construction so they hold only a small amount of refrigerant. While the military unit from Red Dot is about 4" thick and is a copper/brass construction with large round tubes - like you would find on much larger commercial refrigeration systems, etc. Undoubtedly much of the very large system capacity is related to this. The hoses aren't actually overly long compared to a normal pickup truck since the cab-over design moves all the components into closer proximity. The capacity is from those components being MUCH larger than normal. To cope with the desert conditions of the middle east and possibly having the gun turret open while in operation. Personally I didn't want to pair a relatively tiny condenser with the rest of the over-sized components fearing it would be a system bottleneck.

 

[DTinNC]

It seems (based on forum posts and youtube videos) that a not insignificant number of installations are using some aftermarket repurposed automotive style condenser core - usually these are like 1/2" to 1" thick and have VERY tiny flat tube construction so they hold only a small amount of refrigerant. While the military unit from Red Dot is about 4" thick and is a copper/brass construction with large round tubes - like you would find on much larger commercial refrigeration systems, etc. Undoubtedly much of the very large system capacity is related to this. The hoses aren't actually overly long compared to a normal pickup truck since the cab-over design moves all the components into closer proximity. The capacity is from those components being MUCH larger than normal. To cope with the desert conditions of the middle east and possibly having the gun turret open while in operation. Personally I didn't want to pair a relatively tiny condenser with the rest of the over-sized components fearing it would be a system bottleneck.

Yep exactly why I stated that components were one of the variables to charge amount.

I do have the thick condenser to install... But the spec compressor is in (had to machine a bushing and relocate the idler pulley) because I think the comp bracket was aftermarket. The evap box is about to be installed. Looks like the refrigerant lines use the original coolant line holes and that the coolant lines have to go through new holes (to be drilled). Definitely a sizeable job overall. Lol