Minuit

Strange request, but if anyone can find out it's one of you guys. Anyone got some A/C parts lying around and some thread gauges? I need to know some thread diameter and pitch numbers for some A/C parts. 1) Suction and discharge hoses at the compressor end for a '91 thru '93 R-12 system. Measurement can be taken at the hose or at the compressor service valve where the hose connects to the valve, not where the valve connects to the compressor. I expect the discharge fitting to be 3/4-16 and the suction to be 7/8-14, but I don't know for sure. I don't have them on hand to measure. 2) Fittings on the compressor itself, not the service valve, for an '87 thru '90 compressor. I need the thread diameter and pitch where the service fitting screws onto the compressor, not where the hose connects to the service fitting. No idea what this one is or should be.

People really underestimate just how important that auxiliary fan is. I had it die on my '91 a couple of weeks ago and it was immediately noticeable on the temp gauge that something was WRONG at any speed below 30 mph if the A/C was on.

No. The differences between the gold button and white button radios are not really something that can be changed. They're entirely different radios in pretty much every way. For what it's worth, the white button one is much better. For a couple of years ('89 and '90) Jeep used a different supplier for all of their radios, probably for cost reasons. Almost all of the radios made by that supplier sucked in comparison to any other year's radios. Those are the ones that have the brown buttons. Therefore, brown buttons = crappy, cheap radio. The '88 radios are works of art on the inside compared to any other year. They must have cost an absolute fortune to make, so for '89 and '90 they wanted something less expensive. Too bad the '89 and '90 radios were maybe a little too cheap, so for the '91 model year they went back to the same guys who made most of the '84 thru '88 radios. The '91 radios are similar to the '88 radios, with some major simplifications to the internals.

My new favorite MJ story is the All Breeds show in PA and everything going along with it. Take a couple of weeks off work because your idea of fun is driving a 28 year old Jeep 1500 miles round trip to spend a weekend in the company of fellow cool Jeep dudes? Awesome. Do it with an A/C compressor that you got done replacing on a faint suspicion at 9PM the night before you leave... and NOT A SINGLE BAD THING HAPPENS? Really awesome.

@87MJTIM You have two good ones there. The RX-161 (8956001910) is correct for a 1986 or 1987 truck and is quite nice. I generally have good luck repairing everything except the FM tuner section which is a relatively rare failure. I have full repair documentation and a healthy parts supply. The RX-170 (8956002467) is correct for a 1988 truck and is (by a small margin) my favorite sound-wise. They can be somewhat troublesome due to the very large number of connectors inside, which can oxidize or become loose over time, but if working they're a treat. I also have full repair documentation, but parts can sometimes be a challenge since it's a one-year model. Both have XJ brackets on them which makes them a direct fit in an MJ dash. The connectors are different between them - they changed from two 8-pin connectors to one 13-pin connector for 1988. I can perform full service and add auxiliary inputs to both.

At least on the HO sender, I recall an adjustment on one of the pump support ends to make the pump fit tightly. One of the brackets unscrews and allows you to move the bracket up and down. Does that sender have any adjustment in how the pump mounts?

The steadily growing "MJ audio system" copypasta that will hopefully answer the most common questions all at once: Stock speakers are 5-1/4" in the doors and 4x6" in the B-pillars near the cab floor. Depending on your truck's options, your truck may have had speakers in all 4 locations, just the doors, or not at all. Radio delete trucks will have door panels that cover the factory door speaker locations. There are also a set of unused factory tweeter locations on either side of the dash at knee level. These were used in the factory Jensen Accusound 6-speaker system on the Cherokee only. The brackets that come attached to the factory Jensen tweeters can be used for some aftermarket tweeters. For example, Morel Tempo Ultra tweeters fit in the Accusound brackets like they're made for it. Mounting depth is not a major concern in the factory door locations due to the split window design. 6-1/2" speakers can be made to fit in the doors relatively easily, and I don't know what else can fit in the B-pillar speaker locations since I continue to believe that rear speakers in an MJ are useless - AT BEST - unless carefully controlled with a lot of DSP tuning. Subs - you're going to have to come up with your own solution. This could be as simple as a premade powered sub, or as unsimple as building your own frequency tuned box with 800 watts going to the sub. My suggestion is to look up what other people have done in their projects. Use the search function with "sub" or "subwoofer" as keywords. At the time of this writing, Jeep Driver is currently in the middle of an extensive build including audio system. He does good work and I have no problem suggesting his build as a source for inspiration from your system. Search for "Evolution '88" on ComancheClub. As to everything else: I'm a big fan of small amps that can be completely hidden from view. For "low power" (I'll define that as being more than headunit power, up to about 100 watts per channel) builds with 4 or less speakers, my go-to recommendation for an amplifier is the Alpine KTP-445U. 45 watts into 4 channels or 90 watts into two is a huge bump from headunit power, but in a small enough package that it can be hidden from view. There is no shortage of good options here. Cruise Crutchfield's website and see what you like. They are a quality retailer that sell quality products. Now is where you ask "how crazy do I want to get?" No matter the answer, if you want to end up with a vehicle you actually want to get in and drive, you're going to want to do some sound deadening. You'll get just as much improvement out of that as you will throwing subs and amps at the problem. A stock MJ is an absolute tin can. Now that I'm putting my 89 back on the road, it's all coming back to me how noisy and unrefined these things can be. You're going to want to do a lot of deadening to make things livable, and I'm not just talking putting a few sheets of Dynamat on stuff. That'll help (and Dynamat is a quality product), but it won't bring the noise floor down enough for a true "audiophile" system. And then you'll no doubt have plenty of wind noise to worry about once you've done that. The doors on these are especially bad. They're twice as bad if you have power windows. It took a while, but I finally got my doors to stop rattling, but there's a lot of closed cell foam, MLV, and felt in my doors. The time and money spent on sound deadening makes just as much difference as the actual audio parts. The factory attempt at sound deadening consists of a square of vibration damper on each door and a piece of foam on the inside firewall. That leaves plenty of room for improvement. I've made life a whole lot harder for myself by being a fussy purist. By that, I mean I don't want to be able to see ANY audio equipment other than the headunit, which also looks stock. That limits me to the less than great factory speaker positions and a stock-looking radio, albeit one with some secrets under the hood. If you're the kind of guy that chases every percent of improvement at all costs, you'll probably be doing some custom installation sooner or later. Before you spend any money, do some reading on here and other car audio forums and come up with an idea of what you want out of your system. Making sure the sub and amps are going to fit in the truck is the big consideration. Make sure the parts you're picking work well together. For example, if you don't plan on running rear speakers (and my suggestion is to either forget about the rear speakers or use a DSP to control their frequency range) either buy a 2-channel amp or get one that can be bridged to 2 channels. For me, a component set of some type is a must-buy. The dash tweeter locations aren't very good, but having your left tweeter pointing at your ankle is even worse. The best thing to do is build them into either the A-pillars or the sail panels. You may find that you want more flexibility than the passive crossover you got with the component set, so at some point you'll want to go active. That's where I am now. Pretty soon, I'm going to be building a custom "stock" radio with RCA outputs and going 2-way active up front, probably with a MiniDSP 2x4 HD. I'm 90% happy with the way my truck sounds now, but I know I can squeeze more out of it with some tuning. That being said, I'm always trying to squeeze every little bit of improvement I can, within the limits I'm willing to cross. You might do a headunit, amp, sub, and coaxial speakers in the doors and find that you're perfectly happy and don't want any more. That's for you to decide. I don't know your level of car audio experience, so I apologize if I'm telling you things you already know.

The above gentlemen are correct. I'm currently working long hours in a pretty physical job that has me walking 7-10 miles a day, and that includes weekends too. About the most I can do right now is answer PMs on this site and emails, at a reduced rate from before. Send me a message on this site (or another email) and I'll get back to you. I'm just going to leave this here - I am not currently taking new orders at Jeremy's Radio Emporium. I will start taking new orders at some point in the semi-near future after all existing orders are completed. If you would like, I can let you know when I am taking new orders.

Wish I had time to see what's inside of one of these things and see if I could fix it

Pete's Tow Hook Emporium!

Wish I had time to see what's inside of one of these things and see if I could fix it

Hopefully more to come soon.

In this situation, I would always suggest to use the factory gauge... with the stipulation that you use a MOPAR sender only. Aftermarket temp gauge senders are JUNK and not reliable. In my experience, they tend to read higher than a Mopar sender. Aftermarket oil pressure senders seem a little bit more consistent in my experience. Don't complain about how inaccurate the factory gauges are if you stuck crappy aftermarket senders in. The part number you want for most pre '92 applications is 53005309. On the "top" of the sender, there is a threaded stud that the connector attaches to. It does not have a plastic connector molded into it. Starting in 1992, the temperature sender in the rear of the cylinder head changed from a 1-wire to a 2-wire sensor. In 1996, the separate temperature gauge sender was removed and the gauge now pulls its reading from the ECU based on the sensor in the thermostat housing. If both your gauge and sender are working properly (with a MOPAR SENDER), the gauge's needle should be somewhere on top of the "2" in "210" in most cases. This corresponds to a coolant temperature of roughly 195 to 205 degrees. My '91 runs cooler than my '89 due to a larger radiator and the fact that the auxiliary cooling fan is on any time the A/C is on, which is almost always. Steep hill climbs in overdrive and sitting in traffic on extremely hot days are the only cases where I would consider a gauge reading above "on top of the 2" acceptable, and it should immediately return to where it was once you are over the hill or once you have started moving again.

This. Be ready for some serious fumes if you pull the sender with gas still in the tank. The last time I pulled the sender in my '91 I had roughly 1/4 tank and I had to give it a while to air out under the truck before I could breathe.

Maybe a silly question, but can you still see behind you?

As a side note, I want to take this time to address something I've seen repeated quite a lot on this forum - that using "MAX A/C" is bad or runs the A/C harder than normal. In truth, it's actually putting less load on the system on MAX than it is on NORM. On a Comanche, two things happen when you switch from NORM to MAX: - The fresh air door closes and the recirculation door opens, meaning the system is pulling air from the cab and running it through the evaporator, rather than pulling in outside air. The cabin air is probably cooler than the outside air (unless you've been parked outside all day and just started the truck) so the A/C has less heat to get rid of. The longer you run MAX A/C, the cooler this air gets, so even less load on the A/C system! - At least on HO models, it increases the blower fan voltage by roughly 1.5V. That's all. The only component being stressed MORE is the blower motor. That's a valid concern to have, but it won't cause an overheating problem. In the long term, it may melt the fan speed switch if your blower fan is old, shaggy, and drawing too much current and you run the fan on full blast all the time. Even on extremely hot days, I don't need to run my fan on full blast to keep the truck cool (2nd fan speed usually does it, 3rd fan speed if it's REALLY hot), so if you do, you may have an A/C performance problem on your hands. So why does MAX A/C cause less load? Our MJs have an A/C system based on a high pressure cutoff switch and an evaporator probe. Some models have a low pressure switch too, but neither of mine do so we'll ignore it. Those are generally the two things that control whether the compressor is on or off. The high pressure cutoff switch prevents the compressor from turning on if there is no refrigerant in the system or if there is a dangerously high pressure in the system. The evaporator probe controls compressor duty cycle (how often it's on) based on the temperature of the A/C evaporator. Once it reaches a certain temperature (somewhere around 35 degrees, I think) it turns the compressor off. Remember, the evaporator is the part that gets the hot incoming air blown over it, turning it into cold air. The hotter the incoming air is, the more heat gets transferred from the incoming air to the evaporator. The more heat transferred to the evaporator, the more the compressor needs to run to keep the evaporator cold. MAX A/C generally pulls cooler air across the evaporator than NORM does, so the compressor doesn't need to run as much to keep the evaporator cold! I didn't REALLY mean to write a college heat transfer textbook here, but sometimes things happen. Have no fear about using MAX A/C. It's less likely to make your truck run warm than NORM. I pretty much always have mine on MAX. Using the A/C, no matter what setting, will add a significant heat load to the cooling system, so if your cooling system isn't up to the task, turning the A/C on might push it over the edge. If BOTH fans are working properly and your cooling system is in otherwise good condition, this should be no problem. It was 93 degrees this afternoon, and my temperature gauge stayed right where it should with a Mopar temp sender - right on top of the "2" in 210 even when at a stop.

I dream about air conditioning all the time. Maybe I'm not the best example to go by though

My '91 does not have the trim. Both of the older bumpers I have do have the trim.

My first check would be fuel pressure. If fuel pressure is correct, my next move would be to heat the CPS with a heat gun to attempt to reproduce the failure...if you can fit a heat gun in there. If not, I'd try to make it happen again and check CPS output with a meter once the problem resurfaces. If you have to drive it, consider using something to cool the CPS back down. Canned air, bottle of water, whatever. Common trick I use to diagnose thermally-dependent failures in electronics. If hitting it with some freeze spray fixed it, that tells you exactly what part to replace. Or just take the easy route and wing a CPS at it if the fuel pressure is good. That works too, but I don't like to spend money I don't need to.

The '92 wiring will have a LOT of small advantages and some big advantages over '90 wiring. A real exterior fuse and relay box, organized wire runs, the feeling that the thing may have been touched by an actual engineer, etc. Is that all enough to make me want to swap a harness? Maybe if I had to remove everything anyway or was starting from an empty shell. I don't think I'd rip an entire (functional or repairable) Renix harness out of a truck and swap it with an HO harness on its own, though. Lots of changes would have to be made - it won't just slot in unless you swap literally everything from an HO donor. One thing I would NEVER do is backdate an HO vehicle to use anything Renix. Even if it's all I had. I'd rather build my own harness than swap Renix wiring into anything it didn't come in from the factory.

50F is still a very good number considering the Renix era's smaller compressor and various other things. If I remember correctly you're using a stock replacement condenser too. At the end of the day, all that really matters is that YOU HAVE AIR CONDITIONING! A/C in my opinion is the one thing that is always, 100% of the time, completely worth the heartache and cost involved in getting it.

Was that taken with an IR gun? I use one of these: https://www.amazon.com/FJC-2790-1-3-Dial-Thermometer/dp/B0002JMEVC/ref=sr_1_24?keywords=dial+thermometer&qid=1568162983&s=gateway&sr=8-24#customerReviews

I think you know I'm gonna ask - how are your vent temps?