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LMTV Air Conditioner AC Main Unit Gen1 and Gen2 Details
- Thread starter Overdrive
- Start date
bikeracer917
New member
Do you know where the other wire lead goes for the fording switch
Keith Knight
Well-known member
I'll try to help out with the wiring but understand that this is based on my Gen1 Evaporator unit and that you should only do this if you are qualified and fully understand the system. Don't take what I say as fact for all circumstances as yours may be different and you should always verify you wiring before starting.
Wiring diagrams are located in this forum at post #92 for Gen2 and post #134 for Gen1.
Drier: Mine is a 2 switch style, one switch for the High Pressure switch the other one is for the Fan Cycling switch each switch is a two wire switch and are normaly open type.
Each switch requires a ground that is not shown in the diagram so I added it in.
The fan cycling switch can be ran through the fording/engine fan off switch in the dash so it would be turned off with that switch when fording.
After testing I decided to wire the fans to run continuously while the AC is on in an attempt to get it to run as cold as possible. I just wired the Black wire #1 to a ground.
Hope this helps.
Wiring diagrams are located in this forum at post #92 for Gen2 and post #134 for Gen1.
Drier: Mine is a 2 switch style, one switch for the High Pressure switch the other one is for the Fan Cycling switch each switch is a two wire switch and are normaly open type.
Each switch requires a ground that is not shown in the diagram so I added it in.
The fan cycling switch can be ran through the fording/engine fan off switch in the dash so it would be turned off with that switch when fording.
After testing I decided to wire the fans to run continuously while the AC is on in an attempt to get it to run as cold as possible. I just wired the Black wire #1 to a ground.
Hope this helps.
bikeracer917
New member
I'm in the process of installing the evaporator in the cab. Does anyone know exactly how to wire the single black fording wire? Does it just wire to the ground side of the dash panel fording switch?
bikeracer917
New member
Hey Overdrive. Do you know the correct low pressure switch for the ac system? I have the gen 2
Bikeracer917 or anyone else who has installed AC, did you ever figure how to hook up the black wire via the fording switch to disable the condenser fan operation?
I am in the process of installing my Gen 2 unit and am working to get the electrical sorted out.
It doesn't look as simple as hooking the wire up to the fording switch. Based on my studying of the trucks electrical schematics the fording switch switch's 24v on and off not the ground side.
The black wire as pointed out in earlier posts is the ground for the condenser fan and from what I understand should be connected through the high pressures switch to cycle the fan on and off based on temperature.
It seams like the condenser fan ground should go to a high pressure switch that is normally open then tied to ground. the fording switch would the need to be set up to break the ground path to disable the fan.
I haven't figured out yet how to tap into the fording switch circuit without adding a relay to control the condenser ground.
I don't want to reinvent the wheel if someone has already worked out a solution. Perhaps just running the wire directly to ground and having the fan run continuous would be the best solution.
I am in the process of installing my Gen 2 unit and am working to get the electrical sorted out.
It doesn't look as simple as hooking the wire up to the fording switch. Based on my studying of the trucks electrical schematics the fording switch switch's 24v on and off not the ground side.
The black wire as pointed out in earlier posts is the ground for the condenser fan and from what I understand should be connected through the high pressures switch to cycle the fan on and off based on temperature.
It seams like the condenser fan ground should go to a high pressure switch that is normally open then tied to ground. the fording switch would the need to be set up to break the ground path to disable the fan.
I haven't figured out yet how to tap into the fording switch circuit without adding a relay to control the condenser ground.
I don't want to reinvent the wheel if someone has already worked out a solution. Perhaps just running the wire directly to ground and having the fan run continuous would be the best solution.
bikeracer917
New member
Hi. I never finished the wiring. From what I know it's connected to a wire in the dash fording switch. I haven't had time to get to it. And now that winter is here the ac is going to wait till spring. Lol. I did make all my own hoses and did a custom v-belt self tensioner. Everything on my truck is the same setup as the m1078a1-p2 truck.
I originally thought the wire would tap directly into the fording switch however after spending a few hours checking the truck wiring schematics that doesn't seem possible since the fording switch isn't switching the ground side of the circuit. I think it could still be done using a normally closed relay. I will probably never need to override the fan so I may just connect directly to ground or through the pressure switch.
I still need to purchase a condenser/ dryer and fan did you use the LMTV setup or did you go another route?
I also plan to fab the hoses, any advice on sources etc?
I still need to purchase a condenser/ dryer and fan did you use the LMTV setup or did you go another route?
I also plan to fab the hoses, any advice on sources etc?
bikeracer917
New member
Hey... The dryer and condenser/fans are ebay items. Just do some shopping. Paid close to 4 bills for mine. The hoses can be purchased from any automotive ac supply company. I live in Jacksonville Florida. There is a company called tubes and hoses. They are cheaper than ebay. They had everything I needed and fabricate custom stuff. Do you have the sanden compressor? I paid about 360.00 for mine. And it's the correct one.
bikeracer917
New member
You will need condenser and dryer. And hoses and v-belt. Refrigerant. Pressure switches. And Time and money. Lol
Thanks
I knew it sounded too easy. So for @ $500 I can get camper roof air and run an inverter. Other than looking not cool any thoughts on that?
bikeracer917
New member
I have learned from experience that there is only one way to do things.... And that's the right/correct way. Lol. There are modifications that can be done and alot of guys on this site have done them. But do whatever you need to to be cool. Lol.
I have the correct set up using all the correct parts and its less than overwhelming. It will cool the cab down to a point but you've got a lot of area absorbing heat, including whats coming off the engine, and the units are not putting out enough cold air to fully overcome that. You're going to need a bigger unit and a whole lot of insulation to get "car quality" AC.
bikeracer917
New member
I have totally modernized my cab. 3 layers of insulation. It has really quieted down the cab and really insulated it. Really needed here in Florida.
scottmandu
Active member
That is to be expected, you have a windshield the size of USS Nimitz that lets in solar heat and the cab sits on a 230hp diesel fired heater (engine).
bikeracer917
New member
Hey mkcoen. Can you help with a few questions about my gen 2 sysyem? Charged the system but condenser fans and compressor not cycling.
Mine is a gen 1 unit so not sure if there is a difference. We wired the condenser fans to run full time when the unit was on. Not sure why your compressor isn't cycling on though.
I have Gen2 and it's operating fine, I guessing you have a wiring issue. Did you use a binary or trianary pressure switch and how did you wire up the compressor and fan?
Here is how the wiring should be connected
Gen 2 Evaporator
Single pin connector --> connect directly to ground if you want the condenser fan to run continuously or connect thru a trianry pressure switch and the fan will only run when the system pressure is above the switch point (around 230 psi if I remember correctly?)
Two pin connector --> 24V positive and ground either use a 20A inline fuse or a 15A breaker (a 15A fuse will blow since the motor starting current is much higher than the running current)
4 pin connector
Purple --> Condenser fan power
Black --> Condenser fan ground
Green --> Compressor clutch power
Yellow --> Bianary or trianry pressure switch ( the other wire on the pressure switch is grounded)
The remaining connector on the evap unit plugs into the connector that was used on the heater that was removed.
Hopefully this make sense
Here is how the wiring should be connected
Gen 2 Evaporator
Single pin connector --> connect directly to ground if you want the condenser fan to run continuously or connect thru a trianry pressure switch and the fan will only run when the system pressure is above the switch point (around 230 psi if I remember correctly?)
Two pin connector --> 24V positive and ground either use a 20A inline fuse or a 15A breaker (a 15A fuse will blow since the motor starting current is much higher than the running current)
4 pin connector
Purple --> Condenser fan power
Black --> Condenser fan ground
Green --> Compressor clutch power
Yellow --> Bianary or trianry pressure switch ( the other wire on the pressure switch is grounded)
The remaining connector on the evap unit plugs into the connector that was used on the heater that was removed.
Hopefully this make sense
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