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Minuit

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About Minuit

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    MJ Maniac

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    radio-emporium.com

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    Columbia, TN

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  1. I drove my MJ from Tennessee to Pennsylvania and back last year and had absolutely no issues whatsoever. I didn't take breaks and only stopped for gas and food. About 1600 miles in a weekend. The key to it is to make sure you can be confident in the truck. Give everything that could break a once-over. Check every fluid, change if necessary. Make sure every single hose on the entire truck is in good condition and that all the clamps are tight. Check the u-joints for any rust dust around where they spin. Make sure the belt is in good shape, tensioned properly, and that all the pulleys rotate smoothly and without wobbling. Check all of your wheel nuts and make sure they're tight. Make sure the brakes are in good condition. A properly serviced MJ in "confidence inspiring" condition should have absolutely no issue whatsoever driving for as long as you need.
  2. Here we have a textbook example of a tastefully restored truck, but with some upgrades done under the hood to make it more reliable and enjoyable. This is exactly what I like to see, and from a new member to boot. Nicely done. I wonder how many states have a CC member that is using the "MANCHE" vanity plate for their state. I bet it's at least half
  3. Maybe they do, and we've all just gotten used to it I have very little sense of smell and go "noseblind" very quickly. I never can tell what my vehicles smell like.
  4. Sounds like this MJ is in good hands. We all really liked your granddad around here, and it's good to see it passed on to someone who will continue to do it justice.
  5. Yup. No fancy technology in there, but the gauges are designed to work with sending units that work opposite from each other.
  6. This is mainly intended as a response to Eagle, but I think a real fix to this problem would be to swap the fuel gauge to match the sending unit. I haven't tried it, but just comparing the clusters I think it would work out OK. You may or may not be able to keep the low fuel warning light. Torturing a Fuel Gauge for Science Hypothesis: Reversing the connections at the fuel gauge will allow you to use a Renix fuel sending unit in a High Output truck (or vice versa) without the fuel gauge working backwards. Conclusion: NO, the fuel gauge and sending unit must match. Background All Comanche fuel gauges determine the amount of fuel left in the tank by reading the resistance of the fuel level sensor. The fuel level sensor is a variable resistor, that on all Comanches, has a varying resistance to ground based on the fuel level. As the resistance of the fuel level sensor changes, the current passing through the gauge will also change, causing the gauge to deflect depending on the amount of fuel left in the tank. The fuel gauge has three terminals: ignition power, ground, and fuel level sense. The resistance between "fuel gauge sense" and "ground" varies as follows: 1991-1992: 105 ohms when empty. 5 ohms when full. (Source: 1991 Factory Service Manual) 1986-1990: 0 ohms empty, 88 ohms full. (Source: 1990 Factory Service Manual) Other years are outside of the scope of this writeup. Due to this difference in fuel level sensors through the years, replacing the fuel sending unit with one from an incorrect year will result in a fuel gauge that reads backwards. Testing Setup Here's the fuel gauge I will be using for this test, out of a High Output Comanche. While I know this gauge worked when I removed it from my truck years ago, we'll go ahead and test it using the correct resistances for a 1991 model year truck. The ground terminal is in the center of the picture, with a black test lead connected to it. The 12V ignition switched terminal is located to the left with a red test lead connected. The fuel level sense terminal is on the right, and a resistor has been placed between it and the ground terminal. For testing purposes, the fuel sending unit can be approximated by connecting resistors between the "fuel level sense" and "ground" terminals when not installed in a vehicle. With no sending unit connected, the gauge reads below empty. With a 100-ohm resistor connected (I don't have a 105-ohm resistor handy), the gauge should read at approximately empty: To simulate a full tank, I have connected two 10-ohm resistors in parallel between the ground and fuel level sense terminals, creating an equivalent resistance of 5 ohms: Therefore, we can conclude that the gauge is working correctly. Renix Fuel Sending Unit with an HO Gauge As discussed, the Renix-era fuel level sensor reads from 0-88 ohms empty-full. Not only is the scale the reverse of the HO, but the resistance range is different. Just for demonstration purposes, here is what your fuel gauge will read when connected to a Renix sender. Here's two 47-ohm resistors connected in series, which provides an equivalent resistance of 94 ohms: Not exactly 88, but close enough for this demonstration. As expected, the gauge reads empty: Let's try an empty tank - 0 ohms: A very predictable "full" on the gauge. But what if we swapped the gauge connections around? There's three leads, so there's a few different combinations you could make. Let's start by switching the fuel level sense and ground terminals: That's way, way past full, but still a promising start. Let's try an empty tank: The gauge does not move in this position. Why? Remember how the "fuel level sense" terminal reads the resistance between itself and ground? When you switch the "fuel level sense" and "ground" terminals, you connect the fuel level sense pin straight to ground, which pins the gauge at "full" no matter what! Now, I don't think I'm making a controversial statement when I say that reversing the positive and ground terminals on electronics is generally a bad idea. I'm going to do it anyway: Here's 100 ohms: And 0 ohms: I guess it works, just upside down? At least you're on the right side of the gauge. Conclusion In summary, connecting the fuel gauge backwards does not "correct" the gauge in any of the combinations tested here. While this test was done with a High-Output era fuel gauge (with the reasoning that it's much more likely for someone to be installing a Renix sending unit in a High Output truck than the other way around), I believe that repeating this test with a Renix fuel gauge would provide a similar outcome. The gauge and sending unit must match. It looks like the HO and Renix era fuel gauges can be swapped. I do not know about the "low fuel warning module" There are more combinations of leads that could be tried. I tried the combinations that seemed to make the most sense to me. I could test the rest of the possible combinations, but I already have almost two hours of my time into doing this test and writing up the result already. If this is something anyone wants to see more of, let me know.
  7. Based on a quick look at the schematic for the fuel gauge, I don't think reversing the wires would make it work in the right direction. I might have enough spare parts sitting around that I could throw together an experiment.
  8. Nice thermometer. Made some hamburgers, T-bone steaks, and pork chops yesterday. I'm not much of a cook, but they turned out pretty great.
  9. Side note: the Eagle unit gives you no indication of the volume, balance, or fade. I was expecting there to be a little bar on the equalizer at least telling you what the volume is set to, but nope. I thought this was going to be a problem for my upcoming secret project (tm) but nope, that's working as intended.
  10. This thread got stickied? Hmm, I didn't even notice until now. Anyway - for those who have not been keeping up and are only popping in to ask questions or browse through the pretty pictures: From September until April, I had to suspend working in basically anything having to do with these radios due to a very busy - too busy - work schedule. In April I had a medical event that left me "disabled" and unable to work that job for what might end up being forever, so it's back to radios for now. For my first trick, I have managed to locate another hen's tooth: Remember the Eagle Premier head unit I teased a while back? I found the full unit, and fully working too - down to all of the light bulbs. And there's a lot of light bulbs in this thing. Weighing several pounds, fused at 10 amps, and almost maxing out my 3A bench power supply at listening volume, this was essentially the ultimate in Mitsubishi's line of car radios. For 1988, this radio has the best of everything. Featuring a 7-band graphic equalizer, a very fancy (and very effective) AM-FM tuner with some special functions including National Semiconductor's Dynamic Noise Reduction, AM stereo, and station scanning (the only radio of this line to have it). They also managed to shoehorn a fully motorized, computer controlled tape deck with Dolby-B, track searching, and auto reverse into this. It's the same deck as the RX-170 through RX-173. The top unit is not capable of driving speakers on its own - the amplification stage is located in the equalizer. The top unit fits into the same footprint as a standard Jeep radio. The bottom equalizer/amplifier has a special bracket attaching it to the main unit. Power output is modest but typical of the era, rated at 9 watts per channel (36W total) into 8 ohm speakers at 10% THD, and roughly double that into 4 ohm speakers, but heat would likely become a major concern. Construction wise, it's no slouch either. All circuit boards are double-sided with plated through holes, conformally coated, and the typically high quality of components used in all of these Mitsubishi-built radios. I'd compare the older ones to being built like an old home audio receiver. This one is built like a piece of military issue test equipment. It must have cost an absolute fortune to make, and based on some factory pricing information, that cost was definitely passed onto the customer. It actually sounds really good, and the onboard equalizer allows you to dial in the sound you like. It still wouldn't be able to keep up with road and wind noise of your typical Jeep at highway speed though. If you're interested in some gritty details, there's a teardown of a non-working one of these on Allpar here: https://www.allpar.com/stereo/eagle-premier-stereo/default.html The guy doing the teardown calls it the "most sophisticated 1980s head unit combo I have ever seen in any Chrysler product" - I don't know about that, but there are a ton of parts to this. I do have full service documentation for this system if you do happen to own an Eagle Premier with one of these. This isn't the only new thing I have to show off either. More coming later.
  11. Man, good to know it was done by a dealer so it's good to go. And they only managed to lose one of the four screws for the lens. That really soothes my worries.
  12. This used to be the driver seat in my '89. The fabric wasn't nice enough to reuse (and it was the wrong color anyway) but way too nice to throw out, so I took the seat apart, washed the covers, and put the seat back together using a 4DR XJ seat frame on the base for my old workbench chair. The back holes on the frame line up literally perfectly with the back holes on the office chair base. The front holes don't, but there's a hole in the middle of the seat frame already drilled. All I needed to do to bolt it up is drill a matching hole in the office chair base and put it together with nuts and bolts. It makes for a very comfortable office chair, even when sitting in it for a long time. The seat is mounted nosed-up, which may not be to everyone's taste but that's easy enough to fix by elongating the mounting holes a little bit - or by mounting the seat on a "rocker" base from an older XJ. You can also recline the seat. I'll put together a more complete writeup of this at some point, because I took a lot of pics doing it. It also fits the theme of my radio lab
  13. 86 seats will be fine. 95 and newer seats will not fit without considerable modification. Just so it's clear, 1984-1994 seats will bolt right up to a proper set of MJ seat brackets, or to a set of bench seat brackets modified to fit. Or to a standard office chair frame after drilling a single hole, as it turns out.
  14. Minuit

    Grab Handles

    Man, I forget that Tapatalk is even still a thing. CC is fortunate enough to have a pretty good mobile site. Never given me any trouble.
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