Warren99 Posted January 16, 2023 Author Share Posted January 16, 2023 I was just out there looking and noticed that. I think my best course of action is to take apart the hvac box until the accumulator is completely free minus the hoses going thru the firewall, then disconnect the hoses, pull it out of the cab, and immediately reconnect the hoses so the system is sealed again, then it can wait til I'm ready to put the a/c parts in my truck. Is the accumulator the only a/c component on the interior side of the firewall within the hvac box? Link to comment Share on other sites More sharing options...
Pete M Posted January 16, 2023 Share Posted January 16, 2023 some plastic wrap and rubber bands will work too. the evap core is the only thing in the cab. you'll need to disconnect it first in the engine bay before you can even begin to disassemble the puzzle box that is the hvac housing. Link to comment Share on other sites More sharing options...
Warren99 Posted January 16, 2023 Author Share Posted January 16, 2023 Oh ok, but can you elaborate on the plastic wrap part, why is it on the evap core like that when the ends of the hose are wide open, what purpose does it serve? Link to comment Share on other sites More sharing options...
Warren99 Posted January 16, 2023 Author Share Posted January 16, 2023 What’s the process for removing the hvac box from the dash, literally every vid on yt is of a 97+ XJ. I removed the nuts from the studs on the firewall, removed the blower motor, and removed this one bolt from the inside but the box won’t move. It feels like that one big seal is holding it on Link to comment Share on other sites More sharing options...
Pete M Posted January 16, 2023 Share Posted January 16, 2023 take a little square of saran wrap, wrap it over the open ends of the hoses/fittings, then hold it in place with a rubber band. prevents moisture and dust from getting into the system while you're working on things. :) I do the same with most all hoses in a car during disassembly. I didn't cover these because I'm installing a new one. my guess is that you've missed a stud? https://www.cherokeeforum.com/f51/dash-removal-35444/ Link to comment Share on other sites More sharing options...
Warren99 Posted January 16, 2023 Author Share Posted January 16, 2023 Yea I missed the one in the bottom passenger side corner, I forgot to come back to it after the stud started spinning. I'm just gonna cut it but not tonight. And oh ok I thought you were saying the saran wrap to prevent the hoses from bleeding to atmosphere. Link to comment Share on other sites More sharing options...
Pete M Posted January 17, 2023 Share Posted January 17, 2023 yeah, if the system is pressurised, it's going to spew violently once you crack it open. saran wrap isn't going to stop that. if it still has R-12 inside, you should be taking it to a shop to scavenge it. Link to comment Share on other sites More sharing options...
Warren99 Posted January 17, 2023 Author Share Posted January 17, 2023 Alright, but yea the one spun stud was the only thing I was missing Link to comment Share on other sites More sharing options...
AZJeff Posted January 17, 2023 Share Posted January 17, 2023 4 hours ago, Pete M said: yeah, if the system is pressurised, it's going to spew violently once you crack it open. saran wrap isn't going to stop that. if it still has R-12 inside, you should be taking it to a shop to scavenge it. Which brings up a good question to the OP—are you planning on converting to R134a while you are redoing your AC hardware? This is the BEST time to do so, as you can also flush the condenser to get most of the R12 oil out at this time. Link to comment Share on other sites More sharing options...
Warren99 Posted January 17, 2023 Author Share Posted January 17, 2023 I still have a couple of bottles of r12 and a whole new set of components so the plan was to get the r12 running and when it eventually needs recharged, I'll weigh my options between buying more expensive r12 or the r13a swap. I will eventually do a full r134a swap I just wanna use what I have for now Link to comment Share on other sites More sharing options...
Pete M Posted January 17, 2023 Share Posted January 17, 2023 Sell the r12 and do the conversion Link to comment Share on other sites More sharing options...
Warren99 Posted January 17, 2023 Author Share Posted January 17, 2023 Idk, I'm planning on putting the new interior in soon, what all new parts would I need to get from a r134a cherokee? Link to comment Share on other sites More sharing options...
87 MJ Chief Posted January 17, 2023 Share Posted January 17, 2023 I've been told that going from a r12 system to 134 is like trying to make a gasoline engine run off diesel- it's possible but easier/cheaper to just replace the entire system. Link to comment Share on other sites More sharing options...
AZJeff Posted January 17, 2023 Share Posted January 17, 2023 22 hours ago, Warren99 said: I was just out there looking and noticed that. I think my best course of action is to take apart the hvac box until the accumulator is completely free minus the hoses going thru the firewall, then disconnect the hoses, pull it out of the cab, and immediately reconnect the hoses so the system is sealed again, then it can wait til I'm ready to put the a/c parts in my truck. Is the accumulator the only a/c component on the interior side of the firewall within the hvac box? Don't bother to "immediately reconnect" the parts of the system. Once the system is opened even for a few seconds, the system is now "contaminated" by air and moisture, and must be evacuated before being refilled. The reason to cover all the openings you create in the refrigerant plumbing is to keep DIRT out, more than anything else. Link to comment Share on other sites More sharing options...
Warren99 Posted January 17, 2023 Author Share Posted January 17, 2023 8 minutes ago, AZJeff said: Don't bother to "immediately reconnect" the parts of the system. Once the system is opened even for a few seconds, the system is now "contaminated" by air and moisture, and must be evacuated before being refilled. The reason to cover all the openings you create in the refrigerant plumbing is to keep DIRT out, more than anything else. Oh ok so it can theoretically sit with the hoses exposed as long as needed, and I'll be fine if I just replace all the O-rings while installing it, then get it properly evacuated before filling? Link to comment Share on other sites More sharing options...
AZJeff Posted January 17, 2023 Share Posted January 17, 2023 2 minutes ago, 87 MJ Chief said: I've been told that going from a r12 system to 134 is like trying to make a gasoline engine run off diesel- it's possible but easier/cheaper to just replace the entire system. NOT TRUE. I have converted several systems that were designed for R12 into operating on R134a. One just has to follow a bunch of special "rules" when doing so. It IS true that some conversions loose some performance, and that the converted vehicle won't get as cold using the AC with the new refrigerant as it did with R12. However, in the case of an MJ, the HVAC system was designed to cool and heat the interior volume of an XJ, so the little cab of the MJ pickup has much less volume, so the system is overdesigned for that application. That means any losses in performance by switching to R134a won't be noticed in an MJ cab. The important major "rules" to follow in the conversion are the following: 1. ALL old refrigerant MUST be removed by vacuuming the system. 2. A new receiver/dryer (accumulator) must be installed. 3. New refrigerant oil that is compatible with R134a must be added to the system. You get a lot of the old oil when you replace the accumulator, and, in the case of the OP, he is replacing his evaporator, so some more old oil comes out with that, too. (The remaining R12-type oil will not circulate with the new R134a, and thus will settle to the low places in the system, mostly in the condenser.) 4. ALL o-rings must be replaced with ones compatible with the R134a 5. The converted system should be charged with LESS refrigerant than what was called for with R12. The rule of thumb is to use a charge of 80 of what was called for my the factory with R12. Link to comment Share on other sites More sharing options...
AZJeff Posted January 17, 2023 Share Posted January 17, 2023 Just now, Warren99 said: Oh ok so it can theoretically sit with the hoses exposed as long as needed, and I'll be fine if I just replace all the O-rings while installing it, then get it properly evacuated before filling? That is correct. I would cover the hoses with either tape or plastic baggies. (If you use tape, clean any adhesive off when you install the new o-rings.) Be sure to lubricate the new o-rings with refrigerant oil when you install them. Link to comment Share on other sites More sharing options...
Warren99 Posted January 17, 2023 Author Share Posted January 17, 2023 Alright thank you, I'll have to decide what route I go down for now but I have some time. Link to comment Share on other sites More sharing options...
Warren99 Posted January 17, 2023 Author Share Posted January 17, 2023 Do I pretty much have to go to a shop to get the atmosphere evacuated all the way or is it possible to do on my own? My dad has an air vacuum pump and the 3 gauges with hoses. Link to comment Share on other sites More sharing options...
AZJeff Posted January 17, 2023 Share Posted January 17, 2023 26 minutes ago, Warren99 said: Idk, I'm planning on putting the new interior in soon, what all new parts would I need to get from a r134a cherokee? I assume you are transplanting the 97+ interior from an XJ into your MJ, correct? If you are going with parts transplanted from an XJ that had an R134a system, you will need to get the AC compressor from that system as well, and all the various AC lines. The expansion valve used on the R134a systems is totally different than that used on the old R12 system (better, actually), and thus the old lines and compressor would not be compatible with the newer evaporator and expansion valve. Link to comment Share on other sites More sharing options...
AZJeff Posted January 17, 2023 Share Posted January 17, 2023 2 minutes ago, Warren99 said: Do I pretty much have to go to a shop to get the atmosphere evacuated all the way or is it possible to do on my own? My dad has an air vacuum pump and the 3 gauges with hoses. If your dad has refrigeration vacuum pump and a charging manifold (the 3 gauges and hoses), you can recharge the system yourself. Does you dad have experience in evacuating/filling auto AC systems? Link to comment Share on other sites More sharing options...
Warren99 Posted January 17, 2023 Author Share Posted January 17, 2023 17 minutes ago, AZJeff said: I assume you are transplanting the 97+ interior from an XJ into your MJ, correct? If you are going with parts transplanted from an XJ that had an R134a system, you will need to get the AC compressor from that system as well, and all the various AC lines. The expansion valve used on the R134a systems is totally different than that used on the old R12 system (better, actually), and thus the old lines and compressor would not be compatible with the newer evaporator and expansion valve. No its just a black interior from an 87 Chief, I was just saying down the road if I found a r134a cherokee what would I need from it. And I would figure getting a pre 97 would be better for my situation. Link to comment Share on other sites More sharing options...
Warren99 Posted January 17, 2023 Author Share Posted January 17, 2023 17 minutes ago, AZJeff said: If your dad has refrigeration vacuum pump and a charging manifold (the 3 gauges and hoses), you can recharge the system yourself. Does you dad have experience in evacuating/filling auto AC systems? I have no idea how many times he's done it but he has definitely done it before. He's an aircraft mechanic and we do all of our maintenance and projects. We will probably attempt it with the r12 cans I have after swapping everything over. Link to comment Share on other sites More sharing options...
Pete M Posted January 17, 2023 Share Posted January 17, 2023 Technically the only things you need for switching are the 134 ports that come in the kit linked below. BUT a new accumulator is very nice. as is new orings and a 134 specific expansion valve. I'm currently redoing a friend's truck and converting as I go. r-12 has real value these days to guys stuck using it. 134 is dirt cheap. convert while you can and never look back. https://www.amazon.com/Replacement-Expansion-Valve-Compatible-56003173/dp/B0987GKXZS/ https://www.amazon.com/Mudder-VA-LH11-Retrofit-Conversion-Adapter/dp/B07W91FT8T Link to comment Share on other sites More sharing options...
jdog Posted January 17, 2023 Share Posted January 17, 2023 You might also check to see what his gauges are, different refrigerants take different gauges Link to comment Share on other sites More sharing options...
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