Voltmeter Adjustment??

[chopper35nj]

Is there a way to adjust the voltmeter in my Comanche. My Comanche is an 89 and the cluster is from an 89 cherokee. While I had the engine apart to replace the head gasket I thought it would be a good time to replace the alternator because it was now so easy to get at. The old alt. looked like the factory origional and the guage read quite low. I installed a new 100 amp alternator and while I was at it I replaced the battery ground and the engine/firewall ground with 4 ga. copper primary wire. The guage reads higher but nowhere near the 14.4 Volts that I get at the battery.

 

Any thoughts?

 

Thanks

Eric

[cruiser54]

This can be found in this link-Post #18.

 

Also do #1 and add the cables as suggested.

 

http://www.cherokeef...ix-tips-153657/

 

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 knob. 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 knob. 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

[HOrnbrod]

What Cruiser says above is always good. What you want from your dash VM is to read correctly. It's easy to test by hooking a couple of test leads to the terminals in the back of the meter and see what it reads across a known DC voltage, such as your battery voltage as verified to a known good hand-held multimeter. Also the indicated voltage on the dash VM depends upon where the positive sensing lead is connected to.

 

Also, the VMs changed their sensing points several times throughout the years. For instance the HOs use one of the large MAXI fuse outputs in the PDC as the VM sensing point. I changed the VM sensing lead to a common point in the PDC directly connected to the battery's positive terminal. This way I can see the actual charging voltage to the battery rather than watch the voltage drop affected by loads like fans, headlamps, etc.

[chopper35nj]

Thanks Cruiser and Hornbrod good advise. There are a couple of grounds there that I'll have to go back and look at, I still have about six feet of 4ga cable and a half dozen copper lugs. That should cover all my basses. Just to be clear, PDC= Power Distrobution Center, AKA fuse block, right? What you are suggesting is exactly what I'm looking for, an accurate read of the alternators output. Should the sensing lead to the PDC be fused in line or are you saying that it should be attached to a fused circuit already there?

 

Thanks again, great advise.

Eric

[cruiser54]

Thanks Cruiser and Hornbrod good advise. There are a couple of grounds there that I'll have to go back and look at, I still have about six feet of 4ga cable and a half dozen copper lugs. That should cover all my basses. Just to be clear, PDC= Power Distrobution Center, AKA fuse block, right? What you are suggesting is exactly what I'm looking for, an accurate read of the alternators output. Should the sensing lead to the PDC be fused in line or are you saying that it should be attached to a fused circuit already there?

 

Thanks again, great advise.

Eric

 

You have no PDC. You have a fusebox and ECU. Neither affects the dharging system. You have a Delco CS-130 alternator with an internal regulator. Very basic.

[chopper35nj]

OK Cruiser but that dosn't get me where I want to be. Hornbrod's suggestion should still be valid, right? Pick up a large positive lead at the fuse block which should be getting full voltage from the alt. and connect the voltmeter sensing lead to that, that should give me a fairly accurate reading from the alt. I guess my question really was should the sensing lead be fused? Common sense would say yes but, will that get in the way of an accurate read.

 

Thanx

Eric

[HOrnbrod]

The voltmeter is a parallel connection and there is little current flow through the meter movement; no fuse required. Now if you had an ammeter like we used the old days instead of a voltmeter, it would need to be fused since it's in series with the monitored circuit.

[cruiser54]

There is a 7.5 amp "gauges" fuse in the fuseblock per my diagram, that goes to the voltmeter..

 

Check the voltage there.

 

Improving the instrument panel ground made a noticeable difference in my voltmeter reading. As did adding the extra ground cables.