ADVNTURR
I worry when rattles stop
- Location
- Cleveland, OH
I had been looking into doing the A/C to OBA conversion for quite a while and actually started amassing parts a year before I actually got around to doing the conversion. I am going to do my best to provide the most detailed information possible because in my research to do the conversion I found quite a few gaps in others’ write-ups. That being said, this is a lengthy write-up but hopefully it will at least be helpful to someone.
Making Room:
I started the conversion by taking my Jeep to a shop to have the system evacuated (although it has long since lost it charge). I then went under the hood and started removing everything that I could that was related to the old A/C system. I pulled out all of the lines and the old dryer along with the pressure switch (leave the plug for the switch it is used later). I had planned on removing the condenser to open up some additional flow to my radiator, but unfortunately I was unable to remove the nuts from the top of my radiator and therefore could not actually remove it or the condenser. I ended up just cutting the hard lines and then pinching them off with a set of pliers as close to front of the condenser as possible. I also removed the expansion valve at the firewall and cut off and plugged the tubes leading inside to the evaporator to make room for various components.
Inside I had plans to remove the evaporator from under the dash, but after some struggling in my 20deg garage for a night and uncovering a lot of deteriorated plastic, I decided it is going to stay put until this summer when the weather is nicer.
Components:
The goal for my system is to run a 10gal tank I have in the back at 135psi. Here is the list of parts that I used:
Intake (bottom port) listed in order leading to compressor:
Pre-Filter (CCV Filter)
Barb Fitting (3/8 NPT [M])
Oiler (3/8 NPT [F/F])
Barb Fitting (3/8 NPT [M])
3/8 Hose
Barb Fitting (3/8 NPT [M])
Union Fitting (3/8 NPT [F] to #10 [M] 45deg Flare)
Custom Hose (#10 [F] 45deg Flare - #10 [F] O-ring (90deg Elbow))
Output (top port) listed in order leaving from compressor:
Custom Hose (#8 [F] 45deg Flare - #8 [F] O-ring (90deg Elbow))
Union Fitting (3/8 NPT [F] - #8 [M] 45deg Flare)
Barb Fitting (3/8 NPT [M])
3/8 Hose
Barb Fitting (3/8 NPT [M])
Ball Check Valve (3/8 NPT [F/M])
Dessicant Drier (3/8 NPT [F/F])
Union Fitting (3/8 NPT [M/M])
Cross Fitting (3/8 NPT [F/F/F/F])
Reducer Fitting (3/8 NPT [M] - 1/4 NPT [F])
Pressure Switch – 110/135psi (1/4 NPT [M])
Reducer Fitting (3/8 NPT [M] - 1/8 NPT [F])
Pressure Gauge (1/8 NPT [M])
T Fitting (3/8 NPT [F/F/M])
Reducer Fitting (3/8 NPT [M] - 1/4 NPT [F])
Safety Pop-off - 140psi (1/4 NPT [M])
Barb Fitting (3/8 NPT [M])
3/8 Hose
Barb Fitting (3/8 NPT [M])
90deg Elbow (3/8 NPT [F/F])
Flatless Union (3/8 NPT [M/M])
90deg Elbow (3/8 NPT [F/F])
Barb Fitting (3/8 NPT [M])
3/8 Hose
Barb Fitting (3/8 NPT [M])
Female Quick Connect (3/8 NPT [F])
Male Quick Connect (3/8 NPT [M])
90deg Ball Valve (3/8 NPT [F/F])
T Fitting (3/8 NPT [F/M/F])
Reducer Fitting (1/2 NPT [M] - 3/8 NPT [F])
10gal Storage Tank – 135psi
Reducer Fitting (3/8 NPT [M] - 1/4 NPT [M])
Pressure Regulator w/ Gauge (1/4 NPT [F/F])
Union Fitting (1/4 NPT [M/M])
Female Quick Connect (1/4 NPT [F])
In the above list, [F] refers to female connections and [M] refers to male connections. I had a source for the oiler, drier, barb fittings, safety pop-off, and 3/8 hose so I was able to pick up some pretty nice stuff for the price I could have gotten other parts from some place like Harbor Freight. I picked up the regulator, 1 gauge, and the pressure switch off of eBay. The tank I picked up from Sears on sale and it included one of my 2 gauges. The fittings and quick connects were sourced from a combination of Lowes and Hoseandfittings.com.
The most difficult part of the whole process was trying to figure out how to get from the compressor to a readily available fitting (i.e. NPT). I have read on quite a few other write-ups that people are using 3/4 NPT reducers and although they may work, nothing on the A/C system is NPT! I was unable to determine what the exact fitting coming off of the compressor itself was, but at a local A/C shop they were able to identify the ports coming off of the shut-off valves as being a #8 (high pressure) and a #10 (low pressure) o-ring fitting. I had the folks at the A/C shop work up a custom set of lines for me that came from the #8 & #10 o-ring fittings to #8 & #10 45deg flare fittings which I was then able to convert over to NPT with adaptors.
Install:
Install was a lot more difficult than I expected and I ended up having to fabricate a bracket out of sheet metal to hold the oiler for the intake. The bracket bolts to the support that holds the fuse box and the coolant overflow bottle. The bracket is made out of some old sheet metal I had lying around that I plan on someday using to patch the holes in my floor (once I get a welder). I made a template out of some heavy paperboard and test fitted it before tracing the pattern onto the metal and cutting it out with a set of tin-snips. Using a combination of hammers, my 6”vice, and my arbor press I bent it into shape and riveted it together before giving it a liberal coating of underbody coating.
Currently I am just zip-tying the dryer/pressure switch/blow-off to the large wiring bundle on the firewall. I plan to make something more permanent in the spring when it is nicer outside.
To run hose to the back I ended up fishing the hose down through the engine bay and along the inside of the passenger unibody rail using hose clips and rivets through the floor to hold everything in place. This routing does place the hose in close proximity to the exhaust so it is probable a good thing to use some decent quality hose. I ran the hose back to the area under the rear seat where the factory jack equipment resides and drilled a hole through the floor. Using a combination of two 90deg elbows, a hex-less union fitting, and a couple fender washers I made an “S” bend through the floor that is relatively sealed off (I need to add another washer and then use some RTV to really seal it up). From the “S” I ran a short lead of hose out from under the seat into the cargo area where the tank resides and placed a quick disconnect on it so that I can remove the tank if I want.
The tank is currently strapped to my back seat pending a better way to mount it.
For wiring I took a different approach to what anyone I have read has done. I wanted to use as much of the factory wiring as possible so that I did not have to worry about fuses and relays. In the engine bay I ended up cutting off the original pressure switch plug and sectioning in about 18” of wire with soldered and heat-shrunk connections in order to allow me to plug the new pressure switch in as if it were still the old one. This will only work if you have a similar style pressure switch to the one that you pulled off (mine is for an automotive air-ride system and is virtually identical to the factory one). If you use a more traditional pressure switch from a normal air compressor like many people do, you may still be able to use the factory wiring, but not the factory plug.
Inside I followed the lead of an install article I found on this site: http://jeephorizons.com/phpbb/viewtopic.php?p=77144
As in the linked article I pulled the dash panel and then the climate control module to access the wiring. I then clipped and terminated the wires labeled as “A” and “D” on the plug to act as my load (A) and power (D) for my switch. After choosing a mounting location on my center console I soldered leads off of my A & D wires and put female spade connectors on them to attach to the switch. To finalize the wiring I added a short wire off the switch ground terminal and screwed it to the transmission tunnel with a ring connector, sheet metal screw, and a serrated star washer. With the wiring complete I buttoned the dash back up and went about testing the system.
Testing:
The first test of the system proved to be a very frustrating experience which entailed me pulling the entire dash apart again to check connections, a lot of time on my back in the passenger foot well trying to locate and understand the purpose of some factory wiring, and generally being pretty cold. To make a long story short, there is one critical aspect of utilizing the factory wiring and that is the temperature inside of your Jeep needs to be above freezing (probably at least 40deg). The factory wiring utilized a temperature switch buried in the evaporator behind the dash and tells the ECU to shut down the AC clutch relay if there is a chance of icing. Since I was doing all of this wiring in a garage that was ~25deg, it didn’t matter that all of my wiring connections were correct; it was not going to work. After running the Jeep for a while with the heat on, the system worked quite smoothly.
For tire filling duties I typically will flip on the switch on my way out of whatever trail I am on so that the tank will be fully charged by the time I stop and set about the typical on-road prep work. Once the tank is full the Jeep can remain at idle and keep up with tire filling duties. My first practical test of the system I filled a set of 31’s, 30’s, and 35’s from ~18psi up to as high as 40psi without any problems. As we filled tires the pressure in the tank would drop below 110psi and the compressor would kick back in and work the tank back up to 135psi and then shut off. I am still waiting to try and run an air tool off of the system to determine if I am going to rig up some way to run a high idle.
Reflections:
Overall, I am extremely happy with the conversion and despite some difficulties along the way, it was far from the most difficult thing I have done to the Jeep. I did not keep a close tally on my costs, but it was a lot more expensive than many people made it out to be. If I had to estimate I would say that I invested roughly $300 in the entire system. I know there are cheaper ways to do the conversion and in all honesty I could easily have done a CO2 system for much less, but I am left with a very clean install that works well and I trust as being safe.
Hope this helps someone at some point.
Making Room:
I started the conversion by taking my Jeep to a shop to have the system evacuated (although it has long since lost it charge). I then went under the hood and started removing everything that I could that was related to the old A/C system. I pulled out all of the lines and the old dryer along with the pressure switch (leave the plug for the switch it is used later). I had planned on removing the condenser to open up some additional flow to my radiator, but unfortunately I was unable to remove the nuts from the top of my radiator and therefore could not actually remove it or the condenser. I ended up just cutting the hard lines and then pinching them off with a set of pliers as close to front of the condenser as possible. I also removed the expansion valve at the firewall and cut off and plugged the tubes leading inside to the evaporator to make room for various components.
Inside I had plans to remove the evaporator from under the dash, but after some struggling in my 20deg garage for a night and uncovering a lot of deteriorated plastic, I decided it is going to stay put until this summer when the weather is nicer.
Components:
The goal for my system is to run a 10gal tank I have in the back at 135psi. Here is the list of parts that I used:
Intake (bottom port) listed in order leading to compressor:
Pre-Filter (CCV Filter)
Barb Fitting (3/8 NPT [M])
Oiler (3/8 NPT [F/F])
Barb Fitting (3/8 NPT [M])
3/8 Hose
Barb Fitting (3/8 NPT [M])
Union Fitting (3/8 NPT [F] to #10 [M] 45deg Flare)
Custom Hose (#10 [F] 45deg Flare - #10 [F] O-ring (90deg Elbow))
Output (top port) listed in order leaving from compressor:
Custom Hose (#8 [F] 45deg Flare - #8 [F] O-ring (90deg Elbow))
Union Fitting (3/8 NPT [F] - #8 [M] 45deg Flare)
Barb Fitting (3/8 NPT [M])
3/8 Hose
Barb Fitting (3/8 NPT [M])
Ball Check Valve (3/8 NPT [F/M])
Dessicant Drier (3/8 NPT [F/F])
Union Fitting (3/8 NPT [M/M])
Cross Fitting (3/8 NPT [F/F/F/F])
Reducer Fitting (3/8 NPT [M] - 1/4 NPT [F])
Pressure Switch – 110/135psi (1/4 NPT [M])
Reducer Fitting (3/8 NPT [M] - 1/8 NPT [F])
Pressure Gauge (1/8 NPT [M])
T Fitting (3/8 NPT [F/F/M])
Reducer Fitting (3/8 NPT [M] - 1/4 NPT [F])
Safety Pop-off - 140psi (1/4 NPT [M])
Barb Fitting (3/8 NPT [M])
3/8 Hose
Barb Fitting (3/8 NPT [M])
90deg Elbow (3/8 NPT [F/F])
Flatless Union (3/8 NPT [M/M])
90deg Elbow (3/8 NPT [F/F])
Barb Fitting (3/8 NPT [M])
3/8 Hose
Barb Fitting (3/8 NPT [M])
Female Quick Connect (3/8 NPT [F])
Male Quick Connect (3/8 NPT [M])
90deg Ball Valve (3/8 NPT [F/F])
T Fitting (3/8 NPT [F/M/F])
Reducer Fitting (1/2 NPT [M] - 3/8 NPT [F])
10gal Storage Tank – 135psi
Reducer Fitting (3/8 NPT [M] - 1/4 NPT [M])
Pressure Regulator w/ Gauge (1/4 NPT [F/F])
Union Fitting (1/4 NPT [M/M])
Female Quick Connect (1/4 NPT [F])
In the above list, [F] refers to female connections and [M] refers to male connections. I had a source for the oiler, drier, barb fittings, safety pop-off, and 3/8 hose so I was able to pick up some pretty nice stuff for the price I could have gotten other parts from some place like Harbor Freight. I picked up the regulator, 1 gauge, and the pressure switch off of eBay. The tank I picked up from Sears on sale and it included one of my 2 gauges. The fittings and quick connects were sourced from a combination of Lowes and Hoseandfittings.com.
The most difficult part of the whole process was trying to figure out how to get from the compressor to a readily available fitting (i.e. NPT). I have read on quite a few other write-ups that people are using 3/4 NPT reducers and although they may work, nothing on the A/C system is NPT! I was unable to determine what the exact fitting coming off of the compressor itself was, but at a local A/C shop they were able to identify the ports coming off of the shut-off valves as being a #8 (high pressure) and a #10 (low pressure) o-ring fitting. I had the folks at the A/C shop work up a custom set of lines for me that came from the #8 & #10 o-ring fittings to #8 & #10 45deg flare fittings which I was then able to convert over to NPT with adaptors.
Install:
Install was a lot more difficult than I expected and I ended up having to fabricate a bracket out of sheet metal to hold the oiler for the intake. The bracket bolts to the support that holds the fuse box and the coolant overflow bottle. The bracket is made out of some old sheet metal I had lying around that I plan on someday using to patch the holes in my floor (once I get a welder). I made a template out of some heavy paperboard and test fitted it before tracing the pattern onto the metal and cutting it out with a set of tin-snips. Using a combination of hammers, my 6”vice, and my arbor press I bent it into shape and riveted it together before giving it a liberal coating of underbody coating.
Currently I am just zip-tying the dryer/pressure switch/blow-off to the large wiring bundle on the firewall. I plan to make something more permanent in the spring when it is nicer outside.
To run hose to the back I ended up fishing the hose down through the engine bay and along the inside of the passenger unibody rail using hose clips and rivets through the floor to hold everything in place. This routing does place the hose in close proximity to the exhaust so it is probable a good thing to use some decent quality hose. I ran the hose back to the area under the rear seat where the factory jack equipment resides and drilled a hole through the floor. Using a combination of two 90deg elbows, a hex-less union fitting, and a couple fender washers I made an “S” bend through the floor that is relatively sealed off (I need to add another washer and then use some RTV to really seal it up). From the “S” I ran a short lead of hose out from under the seat into the cargo area where the tank resides and placed a quick disconnect on it so that I can remove the tank if I want.
The tank is currently strapped to my back seat pending a better way to mount it.
For wiring I took a different approach to what anyone I have read has done. I wanted to use as much of the factory wiring as possible so that I did not have to worry about fuses and relays. In the engine bay I ended up cutting off the original pressure switch plug and sectioning in about 18” of wire with soldered and heat-shrunk connections in order to allow me to plug the new pressure switch in as if it were still the old one. This will only work if you have a similar style pressure switch to the one that you pulled off (mine is for an automotive air-ride system and is virtually identical to the factory one). If you use a more traditional pressure switch from a normal air compressor like many people do, you may still be able to use the factory wiring, but not the factory plug.
Inside I followed the lead of an install article I found on this site: http://jeephorizons.com/phpbb/viewtopic.php?p=77144
As in the linked article I pulled the dash panel and then the climate control module to access the wiring. I then clipped and terminated the wires labeled as “A” and “D” on the plug to act as my load (A) and power (D) for my switch. After choosing a mounting location on my center console I soldered leads off of my A & D wires and put female spade connectors on them to attach to the switch. To finalize the wiring I added a short wire off the switch ground terminal and screwed it to the transmission tunnel with a ring connector, sheet metal screw, and a serrated star washer. With the wiring complete I buttoned the dash back up and went about testing the system.
Testing:
The first test of the system proved to be a very frustrating experience which entailed me pulling the entire dash apart again to check connections, a lot of time on my back in the passenger foot well trying to locate and understand the purpose of some factory wiring, and generally being pretty cold. To make a long story short, there is one critical aspect of utilizing the factory wiring and that is the temperature inside of your Jeep needs to be above freezing (probably at least 40deg). The factory wiring utilized a temperature switch buried in the evaporator behind the dash and tells the ECU to shut down the AC clutch relay if there is a chance of icing. Since I was doing all of this wiring in a garage that was ~25deg, it didn’t matter that all of my wiring connections were correct; it was not going to work. After running the Jeep for a while with the heat on, the system worked quite smoothly.
For tire filling duties I typically will flip on the switch on my way out of whatever trail I am on so that the tank will be fully charged by the time I stop and set about the typical on-road prep work. Once the tank is full the Jeep can remain at idle and keep up with tire filling duties. My first practical test of the system I filled a set of 31’s, 30’s, and 35’s from ~18psi up to as high as 40psi without any problems. As we filled tires the pressure in the tank would drop below 110psi and the compressor would kick back in and work the tank back up to 135psi and then shut off. I am still waiting to try and run an air tool off of the system to determine if I am going to rig up some way to run a high idle.
Reflections:
Overall, I am extremely happy with the conversion and despite some difficulties along the way, it was far from the most difficult thing I have done to the Jeep. I did not keep a close tally on my costs, but it was a lot more expensive than many people made it out to be. If I had to estimate I would say that I invested roughly $300 in the entire system. I know there are cheaper ways to do the conversion and in all honesty I could easily have done a CO2 system for much less, but I am left with a very clean install that works well and I trust as being safe.
Hope this helps someone at some point.
