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Unread 03-28-2013, 09:54 AM   #1
Quantumspores
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84 Grand Wagoneer - mysterious electrical ghosts?

Folks,

I'm trying to hunt down a phantom electrical problem. Some morning's (about 60% of the time) I start up Waggy and my radio is powered off and my presets are gone. The rest of the day (multiple starts, stops, to/from work) everything will be fine. A while back I replaced the headunit so I know it is wired correctly with the consistent voltage supply. Also, when this happens I have mysterious problems with my gas gauge spiking randomly.

I charged my battery full last night and it was reading 13v turned off and 14.95 with the alternator running. Again today the reading's were the same.

Any thoughts?

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Unread 03-28-2013, 10:12 AM   #2
timgr
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The only thing that determines the charging voltage is the regulator in the alternator. IIRC there are three wires for the Delco alternators - one to energize the field at startup (also operates the indicator light, if present), one for the sense voltage that tells the regulator whether to charge or not, and the charging wire. I believe the sense wire makes a u-turn back to the charge wire, so there's no remote sensing. If the charge wire has a high resistance, this could lead to overcharging the battery, but that's unlikely. Just check that the connections are good, and that there is no measurable resistance between the alternator plug and the positive battery post.

If it still overcharges, then the regulator is suspect. You can buy a regulator and take the alternator apart to replace it, or you can buy a complete replacement alternator. Autozone and likely other stores have a test station where you can test your alternator.

Check what condition will give you a "full" reading on the gas gauge. If zero ohms is full, then you're likely shorting out your wiring somewhere. This could be connected with your head unit wiring. Some head units will maintain presets for a long time without battery power (using a capacitor dedicated to maintaining the memory), some need outside power. I suspect that the newest units use flash memory, and don't need any power source.
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Unread 03-28-2013, 04:11 PM   #3
super98lsc
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check grounds behind the cluster. If the head unit needs a constant power for memory then it will need a 100% solid ground as well. Could be the hu harness is tied to same ground as gas gauge and has th issue
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Unread 03-29-2013, 06:10 AM   #4
Quantumspores
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Anyone know where the dash is grounded? Last time I had the dash off I didn't see any grounding points back there. Does it ground into the engine compartment somewhere?
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Unread 03-30-2013, 08:52 PM   #5
pleontks
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Ground on the heater controls. And one from the 3-wire plug (black) on back of the cluster.

I put mine to my dedicated ground wire.
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Unread 04-05-2013, 06:45 PM   #6
super98lsc
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Dedicated is best same for power. Any high powered head units want the constant power to be a home run to the battery.
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06-Corvette z51-6spd,b&b,K&N low miles.
77-Corvette Stingray 496 BBC/TH400 built 667hp+
===================================
00 WJ 4x4, 4.7 stroker, turbocharged,..lots more..
01 WJ 4x2 4.7v8 Limited (needs valve job)
90 Grand Wagoneer 401 Edelbrock Heads, Lunati .510/.527 FT Cam, Edelbrock RPM Air Gap, Holley HP 750, Thorley Headers, HEI, Electric Fan w Digital controller,4" lift 31x10.50 Goodyear Duratrac's on Pro-Comp Wheels,new interior, seats,seals,Alpine and JL full system, Remote HEI, Clifford 2 way with remote start,windows,tailgate.
96 Cherokee Country 4dr/2x2 White/Tan 3" Lift Sahara 18" Wheels 32.5"'s 99up head and intake- for sale soon!
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Unread 04-05-2013, 07:49 PM   #7
olliehopnoodle
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Ground. Make sure you have a good engine to body ground. Typically the battery negative is attached to the engine. This is so the starter gets the best path for cranking. The starter is one of the highest current usages you have. Then a 'ground strap' is often used from the engine to the body/frame.

Take a decent sized wire from the negative on the battery to a good clean body ground. This will probably fix your issues.
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Unread 04-06-2013, 08:40 AM   #8
super98lsc
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That's a great point Ollie, I added one to the 90. Most newer cars are already that way.
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06-Corvette z51-6spd,b&b,K&N low miles.
77-Corvette Stingray 496 BBC/TH400 built 667hp+
===================================
00 WJ 4x4, 4.7 stroker, turbocharged,..lots more..
01 WJ 4x2 4.7v8 Limited (needs valve job)
90 Grand Wagoneer 401 Edelbrock Heads, Lunati .510/.527 FT Cam, Edelbrock RPM Air Gap, Holley HP 750, Thorley Headers, HEI, Electric Fan w Digital controller,4" lift 31x10.50 Goodyear Duratrac's on Pro-Comp Wheels,new interior, seats,seals,Alpine and JL full system, Remote HEI, Clifford 2 way with remote start,windows,tailgate.
96 Cherokee Country 4dr/2x2 White/Tan 3" Lift Sahara 18" Wheels 32.5"'s 99up head and intake- for sale soon!
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Unread 04-08-2013, 09:35 AM   #9
pcoplin
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On my 85 the connections from the bulkhead plug to the fuse box (on the firewall) was NASTY, and causing 3-4 different intermittent circuits. Might pull it off and clean the terminals just in case.
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