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  #1  
Old 09-19-2018, 07:54 AM
PBG928 PBG928 is offline
232 I6
 
Join Date: Jul 29, 2016
Location: Palm Beach Gardens, FL
Posts: 56
86 GW wiring problems, low voltage

My newly acquired 86 GW has 13v at battery and at new starter solenoid on fender. I have replaced battery cables and positive cable running from solenoid to starter.(later models had a relay on the fender and a solenoid built into the starter) I further replaced all five fusible links that connect to the hot positive post on the solenoid. I also ran new ground to body and engine. When I turn ignition on I get 7.6 volts at the coil and about the same on interior electrical. The windows, ac etc. try to work but at 7.6 volts it is a no go. Starter does not turn over. I can jump it directly but I am concerned about all the other electrical items not working. Dash lights come on dim and gauges seem to move but windows to not go up etc. It would seem all electrical goes through steering column ignition switch and fuse block. It is not just one fuse just low voltage. Any thoughts on where the choke point might be that caused all components to have a drop in voltage? I have not found a shorted wire anywhere yet. Any thoughts would be appreciated. Thanks
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1989 Jeep Grand Wagoneer x 2
1986 Jeep Grand Wagoneer
1985 Jeep Grand Wagoneer
1978 Jeep CJ-5 (sold)
1968 AM General M35 (Sold)
Palm Beach Gardens, FL
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  #2  
Old 09-19-2018, 09:35 AM
ShagWagon ShagWagon is offline
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Location: Oregon Coast
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At least it's a steady 7.6 everywhere. Go backwards till it goes back up to 13.

Try before and after fusebox.
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87 GW- Fitech EFI,Fitech FCC,Skyjacker Hydro 4" lift,BFG AT KO2 30",Dynamax muffler,MSD distributor,MSD 6al box,Blaster2 coil,ACCEL 8mm,.045 gap,Edlebrock perf 4bbl intake,Elgin perf cam,HD alum radiator,Powermaster 150alt,Alum HD H2O pump,Serhills tailgate harness,Cowl screen mod,Evil Twin grab handles,Rstep's custom AMC lock knobs
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  #3  
Old 09-19-2018, 10:34 AM
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babywag babywag is offline
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Join Date: Jun 08, 2005
Location: Land of froot loops and cukcoo-nuts, CA
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There is a resistance wire that drops the voltage to the coil, so if measuring with key on that voltage is normal.

The ignition switch itself might be the culprit, it was on my '90. Replacing it alone resulted in a big increase in voltage.

To find the drop need to measure @ fuseblock, firewall side then move inside until you locate the drop.

Power windows, door locks are frequently poor/corroded master switch(or other switches).

Dim headlights check/clean connectors @ bulbs, and check/clean 2 grounds up front.

All this stuff 30+ years old, and has probably never been touched/cleaned.
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'88 GW (aka Babywag) and '90 GW (aka JUNKbucket) both fuel injected
1994 Caprice wagon
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  #4  
Old 09-19-2018, 11:21 AM
PBG928 PBG928 is offline
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What's odd is everything worked for about a day then voltage dropped down. I get it on the windows and headlights as I have been there and done that, I hate getting under the dash but will start. Will try ignition switch as it is an easy replacement locally available. Thanks
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1989 Jeep Grand Wagoneer x 2
1986 Jeep Grand Wagoneer
1985 Jeep Grand Wagoneer
1978 Jeep CJ-5 (sold)
1968 AM General M35 (Sold)
Palm Beach Gardens, FL
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  #5  
Old 09-20-2018, 10:47 AM
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nograin nograin is offline
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Location: Philadelphia, Pa., USA
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I'll add to Shagwagon's approach.
Might want to make a little sheet to keep track.

Begin at the starter relay and then check down stream under each of these conditions.:
Switch Off.
Switch in Run
Switch in Accessory.

Downstream checks will isolate the problem circuit.:
Headlights. These are on the first 'always hot' fusible link. If you turn the parking lights on, power flows through the fusebox to headlight switch to the markers. Switching to headlights on power flows to the headlight switch direct and then to the headlamps.

Ignition. Hot in 'run'. Off in 'Accessory'. If if you measure after either resistance wire, and current flowing, the voltage will be lower. Easiest place to check the voltage before the resistance wires may be the cavity on the firewall connector.


Fog & Choke Heater relays. I've not looked to see how these are wired in '86.



My drawing says EY, but verify that. First of all I may have not changed it from my '85 for whatever reason. Second, if I did it was probably based on a diagram and I don't recall if anyone here verified that its correct. Along the same lines, the resistance wire as shown reflect the shop manual. According to that, they are no longer in series but dedicated to their respective purposes starting in '86.
If the diagram doesn't show. Go here.
http://www.heritech.org/wagoneer/mggw5a.html
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'85 Grand Wagoneer
360 727auto, NP229
body by beer (PO)
carries wood inside
no "wood" outside
My other car is a fish

Last edited by nograin : 09-20-2018 at 10:55 AM.
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  #6  
Old 09-22-2018, 08:41 AM
PBG928 PBG928 is offline
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Success

Unwrapped electrical tape covering engine wiring found one cut wire that looked old. Got under dash and pulled door chime which had two broken rusted terminals stuck in fuse block. Now I have full voltage inside and accessories work. I think chime must have shorted causing drop. Now chasing neutral safety switch wiring as switch terminals are broken off inside rubber plug next to tranny. This looks like an old problem that PO just bypassed which can be dangerous if in gear. Simple to pull switch and clean out plug and try it. Thanks for help.
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1989 Jeep Grand Wagoneer x 2
1986 Jeep Grand Wagoneer
1985 Jeep Grand Wagoneer
1978 Jeep CJ-5 (sold)
1968 AM General M35 (Sold)
Palm Beach Gardens, FL
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  #7  
Old 09-22-2018, 02:09 PM
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babywag babywag is offline
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can still buy replacement pigtails.
glad you tracked down the problem, keep digging you’ll likely find more issues.
some aerosol elec. cleaner works wonders on plugs/terminals.
lowes and home depot stock it if need?

front door switches always need attention and good cleaning makes world of difference in PL & PW operation.
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'88 GW (aka Babywag) and '90 GW (aka JUNKbucket) both fuel injected
1994 Caprice wagon
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  #8  
Old 09-22-2018, 03:19 PM
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nograin nograin is offline
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Join Date: Dec 19, 2000
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There's a couple of flavors for the connector to the switch in the transmission.
Like Tony posted, the new pigtails are available in bothg flavors - and the combo reverse light/NSS is also readlily available.
My '85 had one 1/2 moon like shown here. http://www.ifsja.org/forums/vb/showthread.php?t=178248&

On my '85 the 3 wires go over the transmission and there's was another connector near heater box on the firewall. I'm pretty sure I disconnected that one from the engine side. This made it easier to splice in the new pigtail.
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'85 Grand Wagoneer
360 727auto, NP229
body by beer (PO)
carries wood inside
no "wood" outside
My other car is a fish
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  #9  
Old 09-25-2018, 06:39 PM
PBG928 PBG928 is offline
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Smile Success Updated: Its the ground wire stupid!

Thought everything was ok after I removed the door chime. Went to 12+volts then dropped back to 8. I had removed the front body cap to have all body parts blasted and painted due to prior damage on drivers side. In process ground wire on drivers side near light relay was cut and not noticeable. Pulled apart wiring harness on my parts car and found complete ground wire. Traced it on my car and found cut black wire that was previously screwed to inner fender well near wiper fluid containers. This one wire if you pull back tape and covering is spliced into 3 or 4 other black wires which presumably function as the main grounds for most accessories etc. As I still have not put wheel well back on I ran a jumper to the firewall temporarily. Voltage went back to 12+ and stayed there. I then was able to bypass neutral safety switch and start the car on the second crank. This car has been sitting in a tow yard for about 6 months. Now I can drive car onto a lift and work on wiring for safety switch as I did put in a new one but apparently not working correctly. Napa sells the wiring harness for this switch as originals get brittle and loose.
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1989 Jeep Grand Wagoneer x 2
1986 Jeep Grand Wagoneer
1985 Jeep Grand Wagoneer
1978 Jeep CJ-5 (sold)
1968 AM General M35 (Sold)
Palm Beach Gardens, FL
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  #10  
Old 05-24-2019, 05:55 AM
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aaronsjeep aaronsjeep is offline
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Location: Pittsburgh Pennsylvania
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Did you figure this out?

Hey PBG928,

I know this thread is old but came across it searching for a separate issue I am working through. (Switching form starter relay to remote starter solenoid for 401 swap.)

Anyway, if you are measuring voltage at the coil after cranking it will be 8 volts. The drop resistance wire in that circuit drops the volts after cranking so as not to burn up the coil. I learned this the hard way when doing an LS swap.

I have an 88 that has chronic low voltage, I suspected the fusible links but after reading through your post going to do some hunting and checking of grounds.

Did you ever find any other smoking guns for your low voltage?
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1987 GW 5.3, 4l60e NP241c

1988 GW 5.3, 4l60e, NP229

1990 GW 6.6, 727, NP229
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  #11  
Old 05-26-2019, 07:29 AM
PBG928 PBG928 is offline
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Yes it was the ground wire that is screwed into drivers inside wheel well that had been cut. Got it working so I can move car around.
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1989 Jeep Grand Wagoneer x 2
1986 Jeep Grand Wagoneer
1985 Jeep Grand Wagoneer
1978 Jeep CJ-5 (sold)
1968 AM General M35 (Sold)
Palm Beach Gardens, FL
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  #12  
Old 05-29-2019, 01:12 PM
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aaronsjeep aaronsjeep is offline
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Quote:
Originally Posted by PBG928
Yes it was the ground wire that is screwed into drivers inside wheel well that had been cut. Got it working so I can move car around.

Thanks!
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1987 GW 5.3, 4l60e NP241c

1988 GW 5.3, 4l60e, NP229

1990 GW 6.6, 727, NP229
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