spudzy

I've been trying to diagnose/repair this problem since last winter and am just about ready to throw in the towel. While driving, I will experience a complete loss of ALL power. The engine will die, radio, blower, etc. will all stop and the Jeep will begin to coast to a stop. About 50% of the time, this power loss will last about 1 second and suddenly everything comes back on and I continue driving. The other times though, the vehicle just dies and I have to quickly put it in neutral and hope that it starts right away so I can continue on my way. Today it happened as I was pulling out into traffic and I thought I was going to get slammed by oncoming traffic. I've read so much here about the crankshaft position sensors. If they go bad, will or can they cut all electrical power to the vehicle? Like I said, when this happens...ALL power seems to disappear. I can't understand how the power to things like the radio, blower motor, etc. can be interrupted when all the while the ignition key remains in the "on" position. Am I even close thinking this is a CPS issue, or do I need to look elsewhere?

freegdr

No codes ? Maybe ignition switch issue?

JerrytheJeep

X2 also what year vehicle what motor are we looking at? Try turning it on and letting it idle, then wiggle every wire you can find. I think you've got a ground issue.

spudzy

No codes are ever set. I've already replaced the ignition switch, neutral safety switch, blower motor, blower motor switch and blower motor resistor since this issue started. I'm really interested in knowing if a faulty crank position sensor will completely cut all power to all components like is happening here with mine. This is a '96 Cherokee with the 4.0 engine.

freegdr

No it wont .What about trying another battery or cables.

spudzy

The battery was less than a year old, but I did remove it and took it back to where I bought it. It tested out great. I have not as yet replaced the battery cables.

freegdr

Loosing power is battery, cables ,ignition switch or cable related, is connection at fire wall tight where main harness attachs to rear of fuse panel below booster?

Pelican

Someone can comment as to whether an ASD relay failing or losing contact could cause a complete shutdown like you're having.

What led to replacing the ignition switch?

spudzy

I haven't checked that particular location yet, but I certainly will. I will also replace the battery cables just to be safe. Thanks for the suggestion.

freegdr

No wont shut of power just motor.

spudzy

I actually switched the ASD relay with another one just to be sure, but that didn't help either. I replaced the ignition switch because when I noticed I was losing not only the engine power, but ALL electrical power...I just assumed everything had to go through the switch for things like radio, blower motor, etc. so perhaps the switch was bad. No luck there either.

spudzy

I forgot to mention one other thing. When I turn on the blower motor to either medium or high, I always see the voltage meter drop significantly (close to 12 volts or less) along with a slight smell of burning plastic or insulation. I checked the alternator output with the blower switch on high and it is 13.8 volts. I don't know if this is related to the shut-down issue or not, but that is why I replaced all the blower motor and switch parts I mentioned earlier.

kennzz05

just a total guess on my part but have you checked the connectors on the computer on the drivers firewall

Pelican

Your alt voltage output is fine with the blower motor on high but what is the voltage at the blower terminals? The melting insulation suggests low voltage that is causing excessive current draw. All of which points to battery cables and connections in poor condition as mentioned above. Unless you've already done so, you need to clean and tighten all battery cable and ground connections just as a matter of course.

The burning insulation/plastic smell could be a connector in the HVAC control unit but the ignition switch connector also sometimes melts as a result of excessive current draw by accessories. And excess current draw by the blower motor is what blows the thermal fuse in the resistor pack.

As a side note, check the continuity across the fuse in the resistor pack you replaced if you haven't tossed it yet. If it measures 0.0 ohms, save the pack as a back-up.

Radi

What did the plug look like? Any signs of discoloration or melting?
In addition to battery cables, check the PDC under the hood- that's the main power entry point. Positive battery cable connects there and supplies power to the rest of the Jeep through a few large fuses, which you should also check.
Signs of heating, discoloration, corrosion, anything loose...
Negative battery cable to engine and engine to chassis connection- that could cause a complete loss of power too.