Voltage drop caused by fried sensor/electrical component?
11-23-2012, 09:48 AM
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Year: 1990
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Voltage drop caused by fried sensor/electrical component?
Alright so I've got a 1990 XJ base model with the 4.0, and I've noticed recently that I have a large voltage drop, mainly on the dash at the gauge but it has caused noticeable changes in how my fuel pump works and how the engine runs. I had a set of fog lights that one of my friends wired up for me, but he basically just stuck the power wire beside a fuse and called it gravy. That worked all fine and dandy until I decided to upgrade to 100w bulbs in these lights instead of 55w. My question is, is there anything on the fuse block that is essential to operation (other than radio and accessories) that would cause a large drop, especially when the lights are on. I also notice that my turn signals cause a large drop too.
11-23-2012, 09:51 AM
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Year: 2001
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Engine: I-6 4.0 L
Well if your alternator hasn't been replaced yet, its pushing 22 years old based on your username. Upgrading may have put enough strain on the alternator to make it go out.
11-23-2012, 03:02 PM
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Well c**p, did forget to mention that, upgraded from the 90 amp stock alt to a 100 amp (woohoo) alt in March.
11-23-2012, 05:19 PM
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Grab a DMM and check wiring at the battery, alternator, etc. and connectors for a high-resistance point. Ground points too. If the alternator and battery are strong, something in the cabling or ground return is acting as a resistor.
11-23-2012, 05:27 PM
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Also alt is good, this has been going on for about 4 months that its read low voltage on the dash, across the battery however reads 13.75 volts
11-23-2012, 05:29 PM
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Year: 1990
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Originally Posted by Radi
Grab a DMM and check wiring at the battery, alternator, etc. and connectors for a high-resistance point. Ground points too. If the alternator and battery are strong, something in the cabling or ground return is acting as a resistor.
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11-23-2012, 05:34 PM
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From what I keep seeing, that dash gauge is not to be trusted. Do you measure good voltage at the interior fuse block? Ciggy lighter socket? If so the gauge is probably lying. OTOH if the voltage really is low at the fuseblock, there's a bad/dirty connection somewhere. Might measure at the PDC and see what you have there.
11-23-2012, 05:50 PM
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By the PDC do you mean the fuse block, or the clusterf*** of wires that's on the starter relay?
11-23-2012, 06:02 PM
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those wires on starter relay are fusable links if one was smoking it could of partiality burnt causing low voltage issue thru it. Check where wires connect and about a foot up on each one for battery voltage .
11-23-2012, 08:17 PM
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Originally Posted by freegdr
those wires on starter relay are fusable links if one was smoking it could of partiality burnt causing low voltage issue thru it. Check where wires connect and about a foot up on each one for battery voltage .
11-24-2012, 05:52 AM
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Ever done this?
Improving the Instrument Panel Ground
The ground point for the complete instrument cluster on your XJ or MJ is located up under the driver’s side dash. If you lay on your back and look up under there with a flashlight, without wearing a hat, you will see a black wire attached to a shiny piece of metal almost directly above the hood release ****. The screw will have either a ¼" or 5/16" head on it.
This ground point is responsible for handling the ground circuit for the following items: Dome lamps, Seatbelt and key warning, trans comfort switch, wiper switch, headlamp switch and delay module, fog lamp switch, cargo lamp switch, all instrument panel grounds and illumination, power windows and door locks, cruise control dump valve, and a few more things.
The problem is that where the ground point is located does not have a good contact with the chassis where the ground should be. The solution is simple.
Make up a jumper wire with #10 gauge wire about 10" long. On one end, crimp on a ¼" round wire terminal. On the other end, crimp on a 3/8" round wire terminal.
Remove the screw from the existing ground wire and attach the small terminal of your jumper so that the original wire and your new jumper share the same attaching point, one over the other.
Look above the driver’s side plastic kick panel just forward of the top of the hood release ****. You will see an 8mm stud there. Attach the large terminal end there with a washer and nut over it tightened securely.
**Special note for Comanche owners: Make your jumper wire 12" long and attach it on the driver’s side kick panel close to the fusebox on the 8mm stud.**
Revised 11-29-2011
11-24-2012, 02:19 PM
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Year: 1990
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Engine: L6 242cid FI I-6
Originally Posted by cruiser54
Did you add the 2 cables as suggested in the ground refreshing write-up?
Ever done this?
Improving the Instrument Panel Ground
The ground point for the complete instrument cluster on your XJ or MJ is located up under the driver’s side dash. If you lay on your back and look up under there with a flashlight, without wearing a hat, you will see a black wire attached to a shiny piece of metal almost directly above the hood release ****. The screw will have either a ¼" or 5/16" head on it.
This ground point is responsible for handling the ground circuit for the following items: Dome lamps, Seatbelt and key warning, trans comfort switch, wiper switch, headlamp switch and delay module, fog lamp switch, cargo lamp switch, all instrument panel grounds and illumination, power windows and door locks, cruise control dump valve, and a few more things.
The problem is that where the ground point is located does not have a good contact with the chassis where the ground should be. The solution is simple.
Make up a jumper wire with #10 gauge wire about 10" long. On one end, crimp on a ¼" round wire terminal. On the other end, crimp on a 3/8" round wire terminal.
Remove the screw from the existing ground wire and attach the small terminal of your jumper so that the original wire and your new jumper share the same attaching point, one over the other.
Look above the driver’s side plastic kick panel just forward of the top of the hood release ****. You will see an 8mm stud there. Attach the large terminal end there with a washer and nut over it tightened securely.
**Special note for Comanche owners: Make your jumper wire 12" long and attach it on the driver’s side kick panel close to the fusebox on the 8mm stud.**
Revised 11-29-2011
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