1988 r30 with newer motor ac problems 7.4 liter

[montrosemafia]

hey guys first time ever posting on a a forum. so i bought a 1988 r30 dually. someone has swapped the motor out to a new motor like a 7.4 OBS 1996-2000 maybe? i am wanting to hook the ac up. is this possible. the wiring looks different on the new motor than what was in there. do i need to buy all new ac parts then custom hose? will the new compressor hook to the controls on the inside of the truck. this has also been converted to a carb and not using the ecm. aby help is appreciated, trying to do it on my own to learn.

 

[Finkaire]

Does the dually have A/C and does the donor engine have a compressor. If all the components are there you might just need to have lines made up. The electrical on the engine side of the firewall is pretty basic. Systems that have been left open are subject to contamination and that is where it can get pricey without guarantees.

 

[Chevy 88]

Ya, I agree - if the truck was originally a factory A/C rig, and the new engine has a compressor - then it should be pretty easy to get it working.

A/C is pretty simple.

A/C is basically two radiators and a pump. One radiator is in the dash, and one is behind the front bumper.
A pump pushes fluid / gas through the system - the same way a water pump pushes coolant through the radiator and heater core.
For electrical, its basically just a power switch, two pressure switches, and an electromagnet that engages the pump.

Its a little more involved then that, that that's a description of the basics.

The simplicity of the system is the reason you can buy a brand new 8,000 BTU window A/C unit for your house for under $100 at Walmart.

It can get VERY expensive if you want it to (for a house or a car). You can spend many thousands of dollars or you can spend under $100. It just depends on what way you want to go.

Before going any further, are all the parts in place?

 

[montrosemafia]

yes the donor engine has the brackets and compressor. i do believe that the dryer and condenser are different on the original 88 truck compared to the engines that in there now. i can buy the new dryer and condenser. I'm just worried that i wont be able to wire it all back up. what do the pressure switches hook to? i can upload pictures in the morning.

 

[montrosemafia]

so short answer is yes. the donor engine has compressor and the original 88 r30 has all the ac components to.

 

[Bextreme04]

yes the donor engine has the brackets and compressor. i do believe that the dryer and condenser are different on the original 88 truck compared to the engines that in there now. i can buy the new dryer and condenser. I'm just worried that i wont be able to wire it all back up. what do the pressure switches hook to? i can upload pictures in the morning.

Post pics. I hate that they swapped in a better EFI engine and then stripped all the benefit out by swapping a carb onto it. I can show you how to properly splice in the AC controls on an L29 motor, but it sounds like they hacked it all up anyways.

 

[montrosemafia]

Post pics. I hate that they swapped in a better EFI engine and then stripped all the benefit out by swapping a carb onto it. I can show you how to properly splice in the AC controls on an L29 motor, but it sounds like they hacked it all up anyways.

yes i wish they would have left it alone i am battling all the issues they didn't take care of. speedo not wokring etc. but i got a smoking deal on a absolutely rust free truck. so i want to try and fix it myself just to say i done it without paying anyone a arm and a leg. i will post some pics tomorrow. thank you for your feed back.

 

[montrosemafia]

Ya, I agree - if the truck was originally a factory A/C rig, and the new engine has a compressor - then it should be pretty easy to get it working.

A/C is pretty simple.

A/C is basically two radiators and a pump. One radiator is in the dash, and one is behind the front bumper.
A pump pushes fluid / gas through the system - the same way a water pump pushes coolant through the radiator and heater core.
For electrical, its basically just a power switch, two pressure switches, and an electromagnet that engages the pump.

Its a little more involved then that, that that's a description of the basics.

The simplicity of the system is the reason you can buy a brand new 8,000 BTU window A/C unit for your house for under $100 at Walmart.

It can get VERY expensive if you want it to (for a house or a car). You can spend many thousands of dollars or you can spend under $100. It just depends on what way you want to go.

Before going any further, are all the parts in place?

yes the donor engine has the brackets and compressor. i do believe that the dryer and condenser are different on the original 88 truck compared to the engines that in there now. i can buy the new dryer and condenser. I'm just worried that i wont be able to wire it all back up. what do the pressure switches hook to? i can upload pictures in the morning.

 

[Bextreme04]

yes the donor engine has the brackets and compressor. i do believe that the dryer and condenser are different on the original 88 truck compared to the engines that in there now. i can buy the new dryer and condenser. I'm just worried that i wont be able to wire it all back up. what do the pressure switches hook to? i can upload pictures in the morning.

If you post pics of what is there now, I can probably help you out. I have done a lot of research and work on swapping a 97 L29 into my 1980 K25. I swapped the sensor on the engine side to a three-wire pressure sensor to run the electric fans and kept the stock 1980 cycling switch on the filter/dryer to cycle the AC using the 1980 AC controls. You would likely be able to do the same thing by modifying the L29 compressor connector to run the ground wire to the chassis and power wire to the light green wire coming from the cycling switch on the filter dryer. The later squarebodies had the condensor with both lines on the passenger side, so a stock L29 manifold hose set will likely attach right to the factory squarebody condensor and filter/dryer, but I am not 100% on that.

 

[Chevy 88]

Basic power path:


Battery > dash switch > low pressure switch > hi pressure switch > electromagnet on the pump.


The low pressure pipe and the high pressure pipe on the A/C have a very basic "on / off" switches on them. If the pressure is tool low then it will trip the low pressure switch and if the pressure is too high then it will trip the high pressure switch. If either switch is tripped, its like turning off a toggle switch - which cuts the power to the pump. You could literally just take a power wire and run it to each switch and then strait to the pump. This would cause the A/C pump clutch to engage and safely disengage when its supposed to. The A/C system is supposed to cycle on and off automatically when the dash switch has A/C selected. Obviously if you ran the jumper wire as described, you would want to disconnect it when the engine off. This is not a suggested way of running the A/C wiring, its just an example that describes how the system operates.

The "defrost" setting on most cars also sends power to the pump clutch, but that is not really relevant to what you are doing at this time.

 

[SquareRoot]

Basic power path:


Battery > dash switch > low pressure switch > hi pressure switch > electromagnet on the pump.

Compressor.

 

[montrosemafia]

If you post pics of what is there now, I can probably help you out. I have done a lot of research and work on swapping a 97 L29 into my 1980 K25. I swapped the sensor on the engine side to a three-wire pressure sensor to run the electric fans and kept the stock 1980 cycling switch on the filter/dryer to cycle the AC using the 1980 AC controls. You would likely be able to do the same thing by modifying the L29 compressor connector to run the ground wire to the chassis and power wire to the light green wire coming from the cycling switch on the filter dryer. The later squarebodies had the condensor with both lines on the passenger side, so a stock L29 manifold hose set will likely attach right to the factory squarebody condensor and filter/dryer, but I am not 100% on that.

If you post pics of what is there now, I can probably help you out. I have done a lot of research and work on swapping a 97 L29 into my 1980 K25. I swapped the sensor on the engine side to a three-wire pressure sensor to run the electric fans and kept the stock 1980 cycling switch on the filter/dryer to cycle the AC using the 1980 AC controls. You would likely be able to do the same thing by modifying the L29 compressor connector to run the ground wire to the chassis and power wire to the light green wire coming from the cycling switch on the filter dryer. The later squarebodies had the condensor with both lines on the passenger side, so a stock L29 manifold hose set will likely attach right to the factory squarebody condensor and filter/dryer, but I am not 100% on that.

 

[montrosemafia]

If you post pics of what is there now, I can probably help you out. I have done a lot of research and work on swapping a 97 L29 into my 1980 K25. I swapped the sensor on the engine side to a three-wire pressure sensor to run the electric fans and kept the stock 1980 cycling switch on the filter/dryer to cycle the AC using the 1980 AC controls. You would likely be able to do the same thing by modifying the L29 compressor connector to run the ground wire to the chassis and power wire to the light green wire coming from the cycling switch on the filter dryer. The later squarebodies had the condensor with both lines on the passenger side, so a stock L29 manifold hose set will likely attach right to the factory squarebody condensor and filter/dryer, but I am not 100% on that.

 

[Bextreme04]

That's definitely an L29 compressor and bracket. Someone has converted it to R134 at some point, because the filter/dryer has the adapter piece on it. You will need to swap that piece over to the new filter/dryer and also make sure the pressure switch is the newer R134 conversion one. The pressures are slightly different and if they kept the R22 one on there, it won't cycle properly.

You are missing the wiring and pigtail for the compressor, and someone cut the hoses off. Depending on how long that has been that way, that compressor might be toast. You will also need a new filter/drier. I would also suggest flushing the whole system with AC system flush before replacing all O-rings and filling the system.

The missing hoses appear to all be from the single manifold/suction/discharge hose assembly. I have not verified if the thread on the assembly matches the GMT-400 hoses, but the dimension of everything are probably close enough for them to reach. Worst case you might need an adapter or for a hydraulic shop to crimp on the right ends to connect to the squarebody components.

You can still get the hose assembly from rockauto or any big box parts store: https://www.autozone.com/cooling-he...ur-seasons-a-c-hose-assembly-56176/730244_0_0

 

[montrosemafia]

That's definitely an L29 compressor and bracket. Someone has converted it to R134 at some point, because the filter/dryer has the adapter piece on it. You will need to swap that piece over to the new filter/dryer and also make sure the pressure switch is the newer R134 conversion one. The pressures are slightly different and if they kept the R22 one on there, it won't cycle properly.

You are missing the wiring and pigtail for the compressor, and someone cut the hoses off. Depending on how long that has been that way, that compressor might be toast. You will also need a new filter/drier. I would also suggest flushing the whole system with AC system flush before replacing all O-rings and filling the system.

The missing hoses appear to all be from the single manifold/suction/discharge hose assembly. I have not verified if the thread on the assembly matches the GMT-400 hoses, but the dimension of everything are probably close enough for them to reach. Worst case you might need an adapter or for a hydraulic shop to crimp on the right ends to connect to the squarebody components.

You can still get the hose assembly from rockauto or any big box parts store: https://www.autozone.com/cooling-he...ur-seasons-a-c-hose-assembly-56176/730244_0_0

i sure do appreciated it. i don't mind buying all new components. to make it right i want to daily this dually when i am done. i can pay someone to do it but i think that's what's wring with the world today i want to learn how to do it. the wiring and vacuum hose is what's scaring me now after speaking with you. i don't know where any of the wiring goes to and from the compressor from low pressure switch and from high pressure switch.