Nakedginger

Hey, so long story short, my old alternator died on me when I was off roading so I got a 100A replacement from Napa for my 1990 XJ. Along with this I got a new serpentine belt. When I turn on any option for the climate control that turns on the blower motor, I have a significant voltage drop. Especially when the Defrost/AC is turned on. I noticed this at idle and tested to see if it went away when I drove around. I went on the highway and the voltage drop stayed the same. As soon as I turn off the AC it goes back up a tad, but hangs around 12V until I turn the blower motor off. I will be going through the grounding wires and supply ( + ) wires coming from the battery. Im also kicking around doing the Big 3 upgrade. My main question is, does anyone have a idea to why this would be happening? any tests I can do to narrow down what it could be? Its definitely not the alternator.

Things I'm considering...

-the Big 3 upgrade
-improving the ground for the alternator?
-blower motor is dying/ maybe had dirt in it
-maybe the serpentine belt is stretching out (but it did this before the new belt)
-wiring to the blower motor is corrupted/wires to the AC compressor are corrupted

Any thoughts or suggestions would be much appriciated since this is what Im doing right now

kjc

Make sure the battery is good and has a full charge.. even a new alt. won't properly charge up a weak or partially discharged battery.

fubar_58

That's all for suggestions? I'm having the same issue with my 98.
I suspect it is my power steering pump. I've been living with this issue for the past 13 months or so.
It's been very good in the cold as.of late. With the blower on high, the sag does.not occur until I use the rear defrost on the window. Even then, I suspect somethin on the serp system is seizing until shut off one of the two, and rarely have to let off the gas for a moment before the squeeling stops.
Looking at the guides on the serp system, I'm thinking there is a sieze happening as most of the surfaces are polished beautifully.
Just today I went and got a used ps pump off a donor 91 xj.
This weekend I will be replacing the bumper, serp belt, alternator, ps pump, and front brakes.
I'm really hoping hoping this will breathe new life into my old work horse.

I'm really doubting this is a charging system issue.

cruiser54

Do the Big 3 for sure. World of difference. Refresh your grounds on that old Renix rig, too.


Renix Ground Refreshing
The Renix era XJs and MJs were built with an under-engineered grounding system for the engine/transmission electronics. One problem in particular involves the multiple ground connection at the engine dipstick tube stud. A poor ground here can cause a multitude of driveabililty issues, wasted time, and wasted money replacing unnecessary components.
The components grounding at the dipstick tube stud are:
Distributor Sync Sensor, TCU main ground, TCU "Shift Point Logic", Ignition control Module, Injectors, ECU main ground which other engine sensors ground through, Oxygen sensor, Knock Sensor, Cruise Control, and Transmission Sync signal. All extremely important stuff.
The factory was aware of the issues with this ground point and addressed it by suggesting the following:
Remove the nut holding the wire terminals to the stud. Verify that the stud is indeed tightened securely into the block. Scrape any and all paint from the stud’s mounting surface where the wires will attach. Must be clean, shiny and free of any oil, grease, or paint.
Inspect the wire terminals. Check to see that none of the terminals are crimped over wire insulation instead of bare wire. Be sure the crimps are tight. It wouldn’t hurt to re-crimp them just as a matter of course. Sand and polish the wire terminals until clean and shiny on both sides. Reinstall all the wires to the stud and tighten the nut down securely.
While you’re in that general area, locate the battery negative cable which is fastened to the engine block just forward of the dipstick stud. Remove the bolt, scrape the block to bare metal, clean and polish the cable terminal, and reattach securely.
Another area where the grounding system on Renix era Jeeps was lacking is the engine to chassis ground. There is a braided cable from the back of the cylinder head that also attaches to the driver’s side of the firewall. This cable is undersized for it’s intended use and subject to corrosion and poor connections at each end.
First off, remove the cable end from the firewall using a 15mm wrench or socket. Scrape the paint off down to bare metal and clean the wire terminal. Reattach securely.
Remove the other end of the cable from the rear of the head using a 3’4" socket. Clean all the oil, paint and crud from the stud. Clean the wire terminal of the cable and reattach securely.
A suggestion regarding the braided cable:
I prefer to add a #4 Gauge cable from the firewall to a bolt on the rear of the intake manifold, either to a heat shield bolt or fuel rail bolt. A cable about 18" long with a 3/8" lug on each end works great and you can get one at any parts store already made up. Napa has them as part number 781116.
A further improvement to the grounding system can be made using a #4 cable, about 10" long with 3/8" terminals at each end. Attach one end of this cable to the negative battery bolt and the other end under the closest 10mm headed bolt on the radiator support just forward of the battery. Napa part number 781115.
For those of us with Comanches, it’s very important to remove the driver’s side taillamp assembly to access the ground for the fuel pump. Remove the screw holding the black ground wire. Scrape the paint from the body and corrosion from the wire terminal. Reattach securely.
　
　
If you want to upgrade your grounds and battery cables in general, contact Jon at

www.kelleyswip.com. He makes an incredible cable upgrade for a very reasonable price.
　
Revised 12-04-2012







Another fix for your low reading voltmeter, dim dash lights, and a host of other issues:
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

95_xj_country

if it doesnt draw as much when the blower motor is on high it could be one of the resistors going bad in the blower motor.

Nakedginger

Thanks , I have seen this modification of yours! I have started doing this. I have replaced and relocated the grounding wire from the engine to the firewall, and started cleaning the stud on the engine. The only thing I have noticed about the stud, recently, is that it is loosening itself. I also have the second cable that you suggested running from the battery to the radiator frame part located at the front of the Jeep. Ill try to install that today. Ill also try that upgraded ground wire for the instrument panel.

If I remember right, the higher I turn the blower motor on, the more it draws.

xj guy

I had noticed that my XJ was drawing a significant amount of power when I put the heat on. The other day, I went to switch it from high to low and I felt a snap in the switch and could tell I broke it. Then some smoke came from the unit.

Went to the JY and pulled a new switch thinking that I had just melted/broke the switch. Low and behold I pulled out the unit to add my new switch and the connection between the two has actually melted together.

I haven't fixed it yet as I am doing more research but check out this write up I found. http://www.jeepforum.com/forum/f11/d...re-fix-580627/

cruiser54

Get that dipstick tube stud problem squared away. It's critical. Good job on the other grounds.

freegdr

If youve done all grounds and still get big draw from blower whats next cruiser ?

cruiser54

Upgrade your cables and do the instrument panel ground upgrade.

freegdr

Done while back still drops?

cruiser54

Huh?

freegdr

Ive done all cable and ground up grades new battery mine drop as soon as ac/blower gets turned on...

cruiser54

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

yarom

Cool. Great tip..