ghetdjc320 Posted January 24, 2020 Share Posted January 24, 2020 Hello all, just removed my dash to get the evaporator core swapped. Turns out that the new part I received from rock auto doesn’t have a temperature probe spot for the old probe. I am on Guam so swapping parts is next to impossible. Can I make this new core work and possibly bypass the temp sensor or reinstall it differently? Link to comment Share on other sites More sharing options...
Minuit Posted January 24, 2020 Share Posted January 24, 2020 That sensor needs to be there. The probe is a temperature sensor that turns the compressor off at a set point (slightly above freezing) to prevent the evaporator from freezing. In most situations it is the only thing controlling the compressor cycling. Aftermarket junk. Link to comment Share on other sites More sharing options...
ghetdjc320 Posted January 24, 2020 Author Share Posted January 24, 2020 So can I just put the temperature sensor probe into the new core? Link to comment Share on other sites More sharing options...
Minuit Posted January 24, 2020 Share Posted January 24, 2020 That is a parallel flow evaporator with refrigerant passing through right where the sensor would have to be. I don't see a way to do it and have it end up even close to OEM. Link to comment Share on other sites More sharing options...
A-man930 Posted January 24, 2020 Share Posted January 24, 2020 I installed the same "different" core in my '90 and have always wondered why the A/C never has gotten cold again... not saying that you'll for sure have the same problem, but it wouldn't surprise me. I happen to have my HVAC box removed for some other repairs; I'd love to get a hold of an OE-type design. Link to comment Share on other sites More sharing options...
A-man930 Posted January 24, 2020 Share Posted January 24, 2020 I guess I always figured that the low pressure cutout switch handled the compressor cycling?? Link to comment Share on other sites More sharing options...
Minuit Posted January 24, 2020 Share Posted January 24, 2020 15 hours ago, A-man930 said: I guess I always figured that the low pressure cutout switch handled the compressor cycling?? There is no low side switch on any 4.0L A/C system I'm familiar with. The only "cutoff" switch is on the high side of the system at the receiver/drier, and its purpose is to prevent the clutch from engaging if there is no refrigerant in the system or there is an excessive high pressure. I do not know what the cutoff points are for the R-12 system, but the R-134a version appears to be closed between roughly 20-450 psi. For this reason I sourced a NOS evaporator for my '91. It was not cheap but I am satisfied with my decision. At low fan speed settings, the clutch will cycle on the temp switch. Increasing the fan speed will keep the compressor running due to the higher volume of airflow. Typical symptoms of a freezing evaporator is a brief period of good (maybe even too good) A/C performance followed by nothing, often accompanied by gradually lower airflow out of the vents as ice collects on the evaporator fins. The system won't cool worth a damn once the evaporator freezes over. Link to comment Share on other sites More sharing options...
Minuit Posted January 24, 2020 Share Posted January 24, 2020 There is an evaporator core available for '87-'90 models that looks much closer to the original design. I wonder if it has the hole for the probe. No such luck for '91 and up. If the probe hole is present on the 87-90 aftermarket evaporator, it could make a much better replacement than the aftermarket ones available for 91+. Will a Renix era evaporator fit in a HO heater box? Link to comment Share on other sites More sharing options...
Gjeep Posted January 24, 2020 Share Posted January 24, 2020 That’s a 97+ xj evaporator core. Not the right one. Link to comment Share on other sites More sharing options...
Eagle Posted January 24, 2020 Share Posted January 24, 2020 Several years ago Advanced Auto had the correct evaporator for my '88 XJ. Sorry I don't have the part number but check 'em out. Link to comment Share on other sites More sharing options...
ghetdjc320 Posted January 25, 2020 Author Share Posted January 25, 2020 When my ac was first installed, I had no high pressure switch and it would never cycle off. A/C still worked just fine though. That temperature switch in the evaporator never did anything (perhaps it was faulty??). Once I retrofit a pressure switch into the line the compressor would cycle on and off. Team cherokee has the oem cores for about $125 right now. I’ll have to grab one I suppose and use it. It just takes forever to ship out here. The core I received from rock auto fits in the opening. I could probably fit the temperature probe into the fins on the side just fine. I may try to get it to work or just get the old style Link to comment Share on other sites More sharing options...
ghetdjc320 Posted January 25, 2020 Author Share Posted January 25, 2020 https://teamcherokee.com/a-c-evaporator-core-assembly-heavy-duty-oem-cherokee-1991-1996/ please save one for me though lol Link to comment Share on other sites More sharing options...
ghetdjc320 Posted January 25, 2020 Author Share Posted January 25, 2020 found The answer I was looking for in post 24 of this thread: https://www.cherokeeforum.com/f46/scarlett-pig-244016/index2/ That is exactly what I’ll do. I’ll let you know how it works. For future reference, although you can find some nos tube and fin evaporators, the part number now interchanges to the newer plate and fin design. It fits well inside the box but does not have a temperature probe provision so one has to fab something up. The 97+ XJs used a low and high side pressure switch. The low side acted as a temperature control switch for the system to keep from freezing up. The 91-96 used the temperature probe and high side switch. As I mentioned before, my temperature switch never shutoff my compressor and my evaporator never froze up even in the heat and humidity of Guam. I’ve had that happen on a mini split ac unit in the house before though. Very annoying lol. The only thing I installed to get my compressor to cycle on and off was the high side pressure switch by the accumulator/dryer. I got a universal inline unit from nostalgicac. Here is the part I used: https://nostalgicac.com/oil-flush-refrigerant-switches/ac-pressure-switch/female-binary-with-inline-switch-port.html when I bought my mj it was stripped clean of every under hood ac part Link to comment Share on other sites More sharing options...
ghetdjc320 Posted January 25, 2020 Author Share Posted January 25, 2020 Indeed this does work. Here are some pics of the conversion and how I decided to go about it: Link to comment Share on other sites More sharing options...
ghetdjc320 Posted January 25, 2020 Author Share Posted January 25, 2020 The plate and fin design should provide more cooling surface area so will report back once installed Link to comment Share on other sites More sharing options...
Minuit Posted January 25, 2020 Share Posted January 25, 2020 Good work. Hard to say how much improvement you'll see. The fact that your temp switch never cycled the clutch makes me think the system is having a hard time keeping up with the heat. Considering where you live that's not a huge surprise. Do you have any vent temp measurements? Are you running a stock or stock-replacement tube and fin condenser? Link to comment Share on other sites More sharing options...
ghetdjc320 Posted January 25, 2020 Author Share Posted January 25, 2020 1 hour ago, Minuit said: Good work. Hard to say how much improvement you'll see. The fact that your temp switch never cycled the clutch makes me think the system is having a hard time keeping up with the heat. Considering where you live that's not a huge surprise. Do you have any vent temp measurements? Are you running a stock or stock-replacement tube and fin condenser? Thanks! The condenser is a stock replacement but I did it a couple of years ago so I don’t remember what I installed. My MJ was in storage for about a year and a half. I also have a triple 10” fan setup that kicks on when the ac comes on or when the engine needs the cooling. Keeps the ac working well even when in traffic at idle. Link to comment Share on other sites More sharing options...
ghetdjc320 Posted January 25, 2020 Author Share Posted January 25, 2020 I’ll try try to get vent temps once it’s back together Link to comment Share on other sites More sharing options...
Minuit Posted January 25, 2020 Share Posted January 25, 2020 12 minutes ago, ghetdjc320 said: Thanks! The condenser is a stock replacement but I did it a couple of years ago so I don’t remember what I installed. My MJ was in storage for about a year and a half. I also have a triple 10” fan setup that kicks on when the ac comes on or when the engine needs the cooling. Keeps the ac working well even when in traffic at idle. A parallel flow condenser will help you eek out a little more performance. APDI makes one that's a direct fit for the MJ. There are also universal fit ones in all ki nds of sizes, but you'd have to figure out brackets and line connections. I've got one of the APDI ones on my 91- I'll get you a number when I get home. Link to comment Share on other sites More sharing options...
ghetdjc320 Posted January 29, 2020 Author Share Posted January 29, 2020 On 1/25/2020 at 11:13 PM, Minuit said: A parallel flow condenser will help you eek out a little more performance. APDI makes one that's a direct fit for the MJ. There are also universal fit ones in all ki nds of sizes, but you'd have to figure out brackets and line connections. I've got one of the APDI ones on my 91- I'll get you a number when I get home. Turns out I have a plate and fin condenser as well. Took me a while to get it all back together since I wanted to do some rewiring while I had it all apart. Now I have a fully restored and functioning cargo light! Taking the Jeep into the ac shop tomorrow to get the system vacuumed and recharged. Hopefully it works well. I worked a lot on the actual ac housing and sealed all the joints. Also replaced the foam in all the seals. I can say that I’ve never been in a car with this much air coming out of the vents lol. Smells much better now that I cleaned out all the crap that was in it. Link to comment Share on other sites More sharing options...
ghetdjc320 Posted January 29, 2020 Author Share Posted January 29, 2020 @Minuit I know this is a bit off topic but I though you would appreciate this being that you have a deep knowledge of how these dashes are put together: Link to comment Share on other sites More sharing options...
ghetdjc320 Posted January 30, 2020 Author Share Posted January 30, 2020 Ok, here are the results we’ve all been waiting for. Went to get it vacuumed and recharged today. The expansion valve will sit about an inch further away from the firewall than the original. The results are... phenomenal! I’ve never had such amazing ac in any vehicle. The temperature is super consistent regardless of fan speed. With the old system it would only be cold up to medium fan speed. I can now blast it on high and it is the same temperature as the low setting. I attribute that to a much more efficient core design. I’m sure that sealing the box and insulating the air gaps around the evaporator helped as well. The heat index was 97 today (actual temperature 85 every day of the year) and it didn’t struggle at all to keep the cab ice cold even in traffic. Please note for future reference that the temperature probe mod works fine and I would recommend the newer core design over the tube and fin setup but it will take some very light mods. If anyone needs this posted as a write-up let me know. Thanks Link to comment Share on other sites More sharing options...
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