Gene

Good troubleshooting so far! Next question: Is it the hot, or the ground, under the dash? May be a bad ground. Are you measuring voltage to the ground wire, or to another ground point? As Rockfrog said, you may be getting voltage (or ground) under the very light load of a voltmeter. But the heavier load of the radio is not supported. This can be a problem on either hot side, or ground side. Can you try a test light, rather than a gauge? Gene

Nice truck!!!!!

If that's your new steering stabilizer- hope it fixes everything! Most likely it will help but not solve the problem. Good luck! Gene

Hi everyone, Sort of off topic here. Universal joints for front axle shafts (88, obviously four-wheel-drive.) My right side has greaseable joint, the grease fitting was in the cross itself. This fitting broke off, every once in a while I try to shoot some grease into the broken stub of fitting that remains. Left side has greaseable U joint, with the grease fitting in the bearing cap. When I grease this, grease will ooze out of three of the bearing caps, not out of the fourth. So I imagine eventually I'll have to replace these. I'd like to stick with greasable, and I think fitting on the bearing cap is better. Yes? No? And if anyone has Spicer part numbers, that would be greatly appreciated Thanks. Gene

Hi paradise, I actually experienced the death wobble (felt like the front end was disintegrating, very very violent shaking) due to tire balance. 88 Comanche totally stock, no lift. Typically at about 60, hit a pothole or bump, the wobble would start and get stronger and stronger until vehicle speed dropped to about 35. Front end was tight. I changed the steering stabilizer, which helped a little. I had the factory alloy wheels, and had trouble getting them balanced well, local shops did not like adhesive weights. So I switched to junkyard steel rims, remounted the old tires, and had them balanced. Death wobble gone and has not come back in 20 years! Gene

http://comancheclub.com/topic/47982-my-death-wobble-trouble-shooting-plan/?hl=death+wobble http://comancheclub.com/topic/46961-violently-shaking-at-high-speeds/?hl=death+wobble&do=findComment&comment=485819 Known problem- check these threads! Gene

Hi Dan, All of this makes no sense. Try this: take one of the radios, go to the battery under the hood. Run one wire from the negative terminal on the battery, over to the radio ground. Run two wires from the positive terminal, one to the always hot, one to the hot with ignition on. If the radio powers up, then there's something going on with the wiring under the dash. If it does not, then the radio is defective. I can't imagine that the antenna connection is the only ground connection to the radio. I don't think the antenna being plugged in should make any difference. I can't comment on the need for the speaker to be connected, I've never run into this. To really make the "direct to battery" test complete, you might have to temporarily connect a speaker in. Good luck! Gene

Thanks Cruiser! Gene

Way to go rocket! Congrats on the fix! Now buy a voltmeter and soldering iron/gun of your own, for future projects..... Gene

Hi everyone, I just checked the Rock Auto website. It appears that they list interchangeability between Cherokee, Comanche, and Wagoneer. Interesting, though. A1 Cardone lists a separate ECU for 87-88, and a different number for 89-90. Standard Motor Parts lists the same ECU for 87 through 90. Gene

Hi everyone, I noticed this comment by Cruiser in another thread: "Get an 89 or 90 ECU regardless of trans. Instant 9 horsepower increase." I'd certainly like a few more horses in my 88 4.0 5 speed. I checked eBay, and they are listing Cherokee and even Wagoneer ECUs as being compatible with Comanches. I would have guessed the ECU would have to come from a Comanche. Comments from the guys who know? Thanks. Gene

Hi paradise, Probably 3 separate issues. 1+2 will be very hard to track down. You may not solve that til it gets worse. 3 sounds like neutral safety switch, especially with it not starting in neutral. 4 may be close to "the nature of the beast see this thread http://comancheclub.com/topic/49226-heater-sapping-power/ Good luck! Gene

That question shows that you "get it!" If the alternator is working properly, you have about 12 V on one side of the bulb, and about 12 V on the other side of the bulb. Since that is equal, no current will flow through the bulb. If the alternator is not working, then there will still be 12 V at the ignition switch side of the bulb, but there will be no voltage at the alternator side of the bulb. (Somehow, in that situation, this terminal becomes grounded at the alternator. I'm just accepting this, I don't really understand it.) So, if the alternator is not producing electricity, then current flows from 12 V on one side of the bulb, to ground that the other side. The above is why I had some reluctance posting. This sounds so goofy it doesn't make sense. Gene

Hi rocket, I'm a little uncomfortable posting this. Normally I like to post stuff that I am reasonably sure about. I'm not as sure about this, much of this is from memory from about 15 years ago, but here goes. For reasons which are totally unclear to me, GM set the alternator up so their are two wires bringing voltage in, to the regulator and field, and one wire bringing voltage out to the electrical system. One of the wires coming in, the yellow, should be hot anytime the ignition is on. How ever, the tan/white wire has to have a 10 ohm resistance in place, before it brings hot to the alternator. The indicator light bulb serves this purpose. So, basically, voltage goes from the ignition switch, through the fuse, through the indicator light, and then down to the alternator. If this fuse is blown, or the light bulb is burned out, then no voltage comes down this wire. The alternator field will not get current, and the alternator will not produce electricity. The test you're referring to, which is very confusing, just wants you to ground the wire going down to the alternator. When you ground that, for test purposes, the circuit then becomes ignition switch to fuse to indicator lights to ground. So then the indicator light should light. If you try this test, and the indicator light does not light, then the fuse is blown, the indicator light is burned out, or there's a problem with the wiring. Now, if you're just in an "I want to get this up and going" situation, I think you can take any source of current which is hot with the ignition on (such as the yellow wire), and connect a new wire to this. Get a 10 ohm resistor, solder this to the new wire, and then connect this where the tan/white wire would go. So current source to 10 ohm resistor to tan/white wire's terminal on alternator. This would disable the indicator light or gauge, but would get the alternator producing current again. As I said, I'm not certain of the above. Good luck! Gene

https://alternatorparts.com/7130-7140.html looks like "Iceberg" kits still available. Gene

Hi hornbrod, Great information (as usual) in this post! I'm surprised at the comment about the reliability of these alternators. A local alternator shop said that they have experienced a very high failure rate with these. Apparently when you have a relatively high output alternator, in a fairly small non-ventilated case, heat builds up, and the heat will kill the diodes. This is especially a problem when the alternator has a prolonged very high output. For example, if you have a dead battery, jump the vehicle to started, and then run to charge up the battery, the extra load will cause extra heat and may kill the alternator. About 15 years ago, when my alternator went bad for the third time, I found an "Iceberg alternator" kit. At that time I bought it from JC Whitney. This had additional cooling on the diodes, I think what was basically flat on the original design had cooling fins that projected externally on the conversion. This alternator has held up for many years. Not much mileage, but lots of time! Again, thanks for the post. Gene

Hi paradise, I actually missed your latest post above, where you posted the voltage readings. Sorry. Based on those, it's overwhelmingly likely the problem is not battery or alternator, but somewhere in the wiring. It still wouldn't hurt to check battery voltage right at the time it's acting up. Gene

Hi paradise, Look at it this way. If the voltage at the gauge is low, there are two possibilities. First, the voltage in the whole system may be low. This would most likely be a bad alternator, much less likely a bad battery. Second, which is more likely, the voltage at the battery and alternator is fine, but it's getting "lost" somewhere in the wiring. Do you have a volt meter? If not, get a cheap one. This should be less than $10 at Harbor freight. It may be called a multi meter. Set the voltmeter on about 20 V DC, and check the voltage at the battery, with the engine off. Typically, a good battery, fully charge, will be around 12.7 V or higher. Then start the engine, and with the engine idling, check the voltage at the battery again. Typically this will be at least 1 V higher, about 13.8 or so. Now, with the engine still idling, turn the headlights and wipers on. The voltage will not be as high, but it still should be over 13 V. To be absolutely certain, carry the voltmeter with you, and when things are "acting up", check the voltage of the battery then. If the voltage of the battery is 13, and voltage at the gauge is 7, then the alternator and battery are good, you're losing voltage somewhere in the wiring. Cruisers tips address this in detail, although apparently there are also problems with the connectors to the ignition switch as well. Finally, the two things you are experiencing may not be related. It's possible that there is a separate problem causing the stalling, not related to the voltage loss. Good luck! Gene

Hi rocket, You are right, there should be voltage at the indicator light socket. There is a wiring diagram in here http://www.bteventures.com//mj1988electricalmanual.pdf page 25 There is a fuse in the circuit too. I doubt it is the ignition switch itself, if all the other "ignition on" accessories work. You're close, keep digging! Gene

Hi rocket, I'm a little rusty at this, but the alternator should have three wires. One is a heavy red one, which is the alternator output. How ever, on another connector are two smaller wires, which are the inputs to the field and regulator. One of them, which is yellow, should be hot whenever the ignition switch is on. The other one is the weird one. It should be tan with a white tracer. It actually feeds through the ignition switch, and then through the voltmeter or indicator light on the dash, then to the alternator. I know, on GM's of this era with an indicator light, if the indicator light burns out, the alternator will not charge. Something about the indicator light putting resistance in the circuit. According to the wiring diagram, I think the gauge works similarly, putting resistance of the circuit. In any case, with ignition on, you should have full battery voltage at the yellow wire connector, and there should be voltage, less than full battery, at the tan/white wire. If there is no voltage at the tan/white wire, a burned-out indicator bulb, or problem with the voltage gauge, may be the problem. I'm not certain of the above, but I remember this with GM's of this era, and it looks like the Jeep wiring diagram is similar. Good luck! Gene

Remove one of the battery cables, loosen the belt, take off the wires and pull it! It's been about 15 years since I pulled mine so I don't remember any more details.... But do charge and test the battery. A failing alternator can kill a marginal battery, and a failing battery can kill an alternator....So there may be two problems... Gene

Hi kawaboy, Agree, bad alternator most likely. Pulling the alternator and having it tested makes the most sense. If the vehicle is stuck somewhere away from home, you can pull the battery, charge it, and see if you can make it home on that charge. Your battery is currently dead, but if the alternator is bad, the battery may just be drained, not defective. Pull the battery, charge it and test it before condemning it. Good luck! Gene

Hi gentlemen, This gets really confusing, but Ohms Law is actually I=V/R or current= voltage divided by resistance Watts (power) = V x I (volts x amps) So if you keep resistance fixed, decreasing voltage DECREASES current flow. So a load that is 120 watts at 12 volts would only be 100 watts at 10 volts. That's why lights dim, or motors run more slowly. The problem is when there is resistance somewhere else in the circuit. Let's say a connection is corroded. There will be resistance at that corroded connection. The voltage drop at that connection actually generates heat. Lets say the current through the circuit is 10 amps. The voltage drop at a corroded connection is 2 volts. So 2 volts x 10 amps= 20 watts of heat will be generated at that connection. That heat will melt plastic, make insulation brittle, and further corrode the connection. More corrosion= more resistance=more heat=more damage. Hence connections fail, wires short, and (worst case) fires occur. So the relay suggested above will primarily make much better connections through the circuit, decrease resistance in the circuit, decrease voltage drop, and minimize overheated connections. Please let me know if any of this does not make sense. Gene

Hi Rockfrog, Sounds like a plan! Where will you be bringing the new wire through the firewall? Are you using 10 gauge wire? Thanks. Gene.

Hi everyone, I may be totally wrong on this, but when I look at the wiring diagram to the MJ, it looks like you have hot from the ignition switch coming into the blower switch, to resistors, to blower motor, then to ground. So the switch and resistors are on the hot side. The XJ wiring diagram above appears to show hot, going to the relay, going to blower motor, then the switch and resistors are on the ground side. If that is right, anything done on an MJ would not be exactly mimicking an XJ. However, the principle is still the same. You still could use one relay on an MJ, going from battery to new fuse to new relay, then from relay over to connection A on the wiring diagram. The relay would be triggered by "ignition on" lead. Sound right? Gene