Manche757 Posted August 31, 2018 Share Posted August 31, 2018 I can not locate a box that holds the ac evaporator and the heater core. Not a new topic. Does anyone know where one can be found? The XJ box is different. It will have to come out of a junker but they don't seem to be available from here to Jesus. Link to comment Share on other sites More sharing options...
HOrnbrod Posted August 31, 2018 Share Posted August 31, 2018 I've never swapped mine, and have never heard the MJ and XJ boxes were different except for w. AC and w/o AC. What makes them different? They carry the same part number in the factory parts manual - item #1 below: Link to comment Share on other sites More sharing options...
Manche757 Posted August 31, 2018 Author Share Posted August 31, 2018 My understanding is that if the MJ never had ac, the box is only large enough to hold the heater core. If the MJ did have ac in the beginning, the box was larger and big enough to hold the heater core and the evaporator core. I had a total replacement done this summer on an 87 MJ that did have ac in the beginning. The mechanic on advice of the supplier installed an oversized MJ evaporator and a new heater core in the existing MJ box without a problem. I want to have ac installed on an 89 MJ that never had ac. That box is not available new. I have not found one used and neither has the mechanic. Although there are fewer MJs left in the junk yards that have not been stripped, I wouldn't think that box would be a highly sought out item anyway. Link to comment Share on other sites More sharing options...
Manche757 Posted August 31, 2018 Author Share Posted August 31, 2018 There is some protrusion on the MJ evaporator that will not fit in the XJ box. In some thread here, there is some discussion about using an XJ box and using an XJ evaporator. I don't know if that works out or not. I would prefer to find a MJ box if that is doable. Link to comment Share on other sites More sharing options...
Manche757 Posted August 31, 2018 Author Share Posted August 31, 2018 I think there is an old thread on CC showing the MJ evaporator not fitting in the replacement XJ box Link to comment Share on other sites More sharing options...
Manche757 Posted August 31, 2018 Author Share Posted August 31, 2018 I do not know if the dashboard controls are available new or not. If anyone knows, please share the knowledge. All the ac hardware is easily available. Link to comment Share on other sites More sharing options...
Manche757 Posted September 1, 2018 Author Share Posted September 1, 2018 The parts manual suggest the information I have gleaned from past threads is wrong. Unkown is what is needed about wiring harness. Is that an OEM parts manual that is online? Link to comment Share on other sites More sharing options...
cruiser54 Posted September 1, 2018 Share Posted September 1, 2018 I think you got some misinformation somewhere along the line. Link to comment Share on other sites More sharing options...
Manche757 Posted September 2, 2018 Author Share Posted September 2, 2018 I think you are very, very right! If you are willing, have a look at the following link. Both my MJ's are 4.0 5 speeds. An 87 and an 89. Part of the middle of the thread is for 2.5s which is not relevant for me. Member 835 appears to have had knowledge and experience but it he both joined and last visited CC in 2011. Notice the pics posted by Comanchmodder on June 20, 2014. He last visited CC in 2015. Has anyone out there actually done this? If so, please comment on the need for changing the wiring harness, which I assume is not available new? Does anyone know if the dashboard controls are available new? Link to comment Share on other sites More sharing options...
Gjeep Posted September 2, 2018 Share Posted September 2, 2018 I’ve pulled apart and pieced together a MJ / XJ HVAC box. Went over the parts in detail. They are interchangeable. You can either get a complete XJ ac HVAC box and put it in the MJ. Or get the evaporator side of the XJ box only and attach to the MJ heater core side. Link to comment Share on other sites More sharing options...
Manche757 Posted September 2, 2018 Author Share Posted September 2, 2018 5 minutes ago, Gjeep said: I’ve pulled apart and pieced together a MJ / XJ HVAC box. Went over the parts in detail. They are interchangeable. You can either get a complete XJ ac HVAC box and put it in the MJ. Or get the evaporator side of the XJ box only and attach to the MJ heater core side. So the box is actually two parts? Junk yard would probably want the same money for both parts as just one. Do you know if a diff wiring harness is needed and if so will that have to come from a junker also? Link to comment Share on other sites More sharing options...
Gjeep Posted September 2, 2018 Share Posted September 2, 2018 Yes, it’s 2 parts that bolt together. Some have a foam insulation inside. Kind of a liner/ filter to catch dust I believe and others are just raw plastic. The older era XJ’s seemed to more consistently have the liner. The newer ones don’t. As for the wiring, it depends on your year. It would be easiest to just grab the entire harness assembly as your MJ may not have the provisions both under the hood and under the dash. Dash additional wiring is minimal...just for the evaporator thermister. Under the hood there will be relays and wiring to the cut-off switch, etc. I’ve always done it the hard way, if my wiring is good, I don’t risk getting a complete underhood harness for example that might have issues. I’ll take the time to just remove the wiring I need and add it into my harness both interior and underhood side. Link to comment Share on other sites More sharing options...
Manche757 Posted September 2, 2018 Author Share Posted September 2, 2018 15 minutes ago, Gjeep said: Yes, it’s 2 parts that bolt together. Some have a foam insulation inside. Kind of a liner/ filter to catch dust I believe and others are just raw plastic. The older era XJ’s seemed to more consistently have the liner. The newer ones don’t. As for the wiring, it depends on your year. It would be easiest to just grab the entire harness assembly as your MJ may not have the provisions both under the hood and under the dash. Dash additional wiring is minimal...just for the evaporator thermister. Under the hood there will be relays and wiring to the cut-off switch, etc. I’ve always done it the hard way, if my wiring is good, I don’t risk getting a complete underhood harness for example that might have issues. I’ll take the time to just remove the wiring I need and add it into my harness both interior and underhood side. What are your thoughts about foam liner or not. I would think the foam has disintegrated after 30 years but would provide some proofing if there. Curious that the progression was away from foam. Your pulling only the wires needed from the donor harness and not disturbing the others makes a lot of sense. The install will be for an 89 4.0. 5 speed. The controls will be by cables to the dash and not electric? If the dash controls have to come out of a junker I wonder how well 30 year old cables and controls will work. Link to comment Share on other sites More sharing options...
Gjeep Posted September 2, 2018 Share Posted September 2, 2018 The boxes with liners that I have found have held up well over the years. I live In California though and temperatures throughout the year isn’t that drastic. I’m sure extreme temperatures take its toll on the foam. I’m going to run the box with the liner. As for the controls, the high/ low fan switch is electric while the HVAC controls are vacuum. The vacuum harnesses I’ve seen in the yards have always been good. It’s a soft, not brittle colored vacuum hose assembly. Link to comment Share on other sites More sharing options...
Manche757 Posted September 2, 2018 Author Share Posted September 2, 2018 Any best guess which years have liners? Link to comment Share on other sites More sharing options...
Gjeep Posted September 2, 2018 Share Posted September 2, 2018 88-92 XJ’s Laredo and Limited trim should have the liner. Know that the thermistor you will need to use is renix era only. 87-90. The deletion of the liner I’m guessing was due to cost saving/ profit. Link to comment Share on other sites More sharing options...
Manche757 Posted September 2, 2018 Author Share Posted September 2, 2018 You are hereby appointed the CC a/c resident guru. Thanks for the help Link to comment Share on other sites More sharing options...
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