Solenoid bypass - bad idea? -

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post #1 of 6 Old 07-10-2009, 01:59 PM Thread Starter
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1976 CJ7 
Join Date: Jul 2009
Location: Tennessee
Posts: 16
Solenoid bypass - bad idea?

I just bought a '76 CJ7, my first jeep, and the last week has been spent chasing down an electrical issue. The starter and solenoid have been replaced, the battery recharged (it was dead), and the alternator run through a diagnostics instrument. However, when the engine was started and a battery cable removed, the engine would quit. The guy at auto-zone eventually suggested a jumper between my alternator positive terminal and my battery terminal and skipping the solenoid, which worked, but I'm not too comfortable with completely bypassing a part of the ignition system.

The alternator has an internal regulator (which according to the AZ diagnostics works), but I'm still worried that I might be overcharging the battery and setting myself up for a major disaster down the road if I try to use this as my long term fix.

Any thoughts?

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post #2 of 6 Old 07-10-2009, 03:41 PM
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1973 CJ5 
Join Date: Aug 2007
Location: South West Indiana
Posts: 11,180
First off, WELCOME to the wonderful world of antique Jeep vehicles!

This is going to be a steep learning curve, and not everyone claiming to be an 'Expert' knows a lug wrench from pancakes when it comes to CJ Jeeps...

Your charging system was working correctly, and the guy that suggested a 'Jumper' was an idiot.

This hasn't been a viable way to test any ALTERNATOR,
And it normally only works on DC Generators, which you don't have.

Your vehicle is supposed to die when you remove a battery cable because you are cutting power to the ignition module and coil when you remove a battery cable...
Has NOTHING to do with the alternator.

The alternator has to sample the battery to figure out how much current to put into the system.
When you break that 'Sample' circuit, the alternator shuts down to keep from overloading the rest of the electrical components in your vehicle.


Since you never actually told us what the 'Electrical Problem' was,
We can't help with the 'Issue' at hand!
(but I'm sure it has to do with the 33+ year old wiring in the engine bay)

Since you say you have a '76 CJ, and it has a 'Internal Regulator',
I'm assuming you have an I-6 engine since the Delco Remy 10 SI alternator never came out on the '76 V-8 engines...

Please remember to fill out your Bio information so we know what 'Heep' you have and what engine we are dealing with.

Your biggest problem is probably the electrical 'Ground' to the alternator.
It's always a good idea to provide a dedicated 10 Ga. 'Ground' wire directly to the alternator case.

The Delco Remy SI and CS series of alternators are wired to STOP charging if the battery is disconnected (accident, fire, ect.) and it is a SAFETY ISSUE.
You REALLY don't want to defeat that built in safety or you could have as much as 250 Volts AC running through your 12 Volts DC vehicle.

Voltage from your alternator should be around 14.5 volts max,
With an Amperage limit of about 65 amps.
If it's a direct replacment, your alternator should be a 42 Amp unit.
Some of the early Jeeps had as low as 37 Amp units, but those haven't been made for a LONG time, and have been replaced by 42 Amp units and up...

Your vehicle will NEVER draw more than about 40 Amps for very long, so there REALLY isn't a reason to put a huge alternator on a Jeep...
(Dual batteries on the other hand should be mandatory for trail or work Jeeps!)

Here is the place to find the alternator nomenclature...

Last edited by JeepHammer; 07-10-2009 at 03:59 PM.
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post #3 of 6 Old 07-10-2009, 04:12 PM
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1964 CJ5 
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Location: Littleton, CO
Posts: 263
Which solenoid terminal was the alternator output connected to? If it was connected to the solenoid end of the battery cable, moving it to the other end of that cable should not make any difference. If it was connected to any other solenoid terminal, it was wrong.

If the alternator was working when the engine was running, and if it was connected correctly, disconnecting the battery should not kill the engine. The alternator produces plenty of power to operate the ignition. You can jumpstart a car with a completely dead battery and the alternator will keep the ignition system running even while the battery is still dead.

Last edited by CO64CJ5; 07-10-2009 at 04:30 PM.
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post #4 of 6 Old 07-10-2009, 05:49 PM Thread Starter
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1976 CJ7 
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Thanks for the info so far. I suppose I did sort of handicap everyone, so here's what I know:

The engine IS the 258 I-6, and the alternator that is in it is a remanufactured delco-remy that was bought and installed just before I bought it.

I'm having problems uploading an image, so I'll just have to try to explain how it's wired. The large solenoid terminal facing the firewall has two leads connected to it, the main line to the positive battery terminal and a 10-guage line that runs to the battery meter inside. The large terminal on the side facing the front has a wire running to the starter. Two smaller terminals on the side connect to two wires that disappear into the firewall. The main line from the alternator runs into a split that is decidedly NOT factory. One of the leads runs to the battery meter, the other to the fuse box. A smaller lead from the alternator's positive terminal goes into a two-lead clip on the side of the alternator.

Does any of this sound obviously wrong?
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post #5 of 6 Old 07-10-2009, 06:54 PM Thread Starter
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1976 CJ7 
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One last symptom that just came up when I was putting everything together: I brushed the circuit board housing attached to the wheel well and noticed it was hot.
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post #6 of 6 Old 07-11-2009, 07:33 AM
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1964 CJ5 
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Location: Littleton, CO
Posts: 263
I don't know what the circuit board housing is -- ignition module?

When you say "battery meter", what is this -- ammeter, or voltmeter? The way you describe it, it should be an ammeter. Just to clarify, one side of this meter is connected to the 10ga wire from the solenoid, and the other side is connected to the alternator's output?

The "two-lead clip" on the alternator -- is the other lead connected to anything?

Do you have a multimeter or test light?
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