Wireing Question?

Confirm if I am correct.

With battery disconnected and reading on the positive battery cable, I should not be getting a reading on a voltmeter set to just check continuity. If I'm getting a reading I've got a wire shorted? Someone told me the positive cable should be openwhen disconnected from the battery.

Right or wrong.

Still trying to chase down my eletrical problems.

 

hey i've thinkin bout your problem, and wondered? maybe? a bad ignition switch? see i you gotta power drain, it could be the fiber chip in the switch. you may turn it off with the key, but... is it off? radio on, guage lite on? remember. i've seen it before. danchuk mfg. recalled their repops for this very reason.you'd turn the key off but power would still trickle out through the bad switch and wham kill the batt the next mornin.and*****s to have the last car in the shop to have a dead battery. you said your chargin systm was ok. so i've been researchin and came to this, try it out , oreilly auto parts should have an ign. switch in stock, at least they do here. its a shot. your battery, starter hot runs through then to the second halve of the fuse panel, check it out, let me know

 

Sideburns, almost called you last night but had more checking to do. When the light and radio stayed on the ignition switch was first thing I checked. Light stayed on with the switch completely removed. After I replaced the regulator those problems went away.I thought that the light only ran from the swith so that seemed odd. I thought system was charging but had the battery drain. Upon further checking, alternator was bad. It did pass the pull cable and car kept running test you told me to do so it must have been putting a little out but not enough to charge the battery fully. Took it off and had it checked. Replaced and everything seemed fine. Car was cranking strong and all seemed well till I noticed the radio was'nt working. (radio only had blown fuse).

While checking around at the fuse box to make sure radio had power, key was turned on and off several times and car was cranked many times. After turning car off I heard a strange noise and looked under the hood to see new alternator frying. Had to disconnect battery to stop it.After telling some stories at O'reilys I got them to replace my alternator and I picked up another (cheaper) regulator for the car. At this point I'm scared to hook anything up.My book says a bad alternator will kill a regulator. Was wondering if it killed my new one which then turned around and killed the alternator. I dunno seems funny it was fine for quiet a while then it just sizzeled. Right now I'm checking wires for shorts.

The positive battery cable reads as being grounded. I was not sure if this was right or not. Been told it should read open.

So thats what I'm needed to know at this point. If it should read open, I'm going searching through everything tonight trying to pinpoint where a short could be.

 

Don't think the "pull the battery cable" works with an alternator. I think that test is just for a generator.

Also, don't try to polarize anything with an alternator. Not sure if it hurts anything, but it is not needed like with a generator.

 

Why are you running a regulator with an alternator? A regulator is a device that is used with a generator. An alternator is an AC device and has a built- in rectifier to convert the AC to a regulated DC...

 

Not all alternators are internally regulated, some reqiure an external regulater. The diodes inside the alternator change the AC to DC, but don't regulate the volt/amp output.

 

I learned the hard way several years ago that you don't pull the wire off the alternator when the car is running or you'll burn it out.

I usually just use a self powered test light on the negative battery cable to check for voltage drain. I remove the battery cable and then connect the clip to the cable and the pointer to the (-) terminal on the battery. If the lights on their is a drain and then I start pulling fuses to find the drain.

 

[ QUOTE ]
Why are you running a regulator with an alternator? A regulator is a device that is used with a generator. An alternator is an AC device and has a built- in rectifier to convert the AC to a regulated DC...

[/ QUOTE ]

Um, rectifiers or diodes as they are sometimes called don't "regulate" the power output. You need a regulator to regulate it.

What exactly is the problem? I don't understand. Dave

 

Charlieled, Big dog hit it. My wireing diagrams actually call it a AC generator. Mine takes an alternator with a external regulator.

Joes50, I don't think I have a drain anymore. My alternator was bad not letting the car charge.My dad actually called today and said not to run it with the wire off the alternator or it would ruin it so I found that one out before learning the hard way.

 

All GM manuals call the alternator a "AC generator", but no matter what you call it, it's still an alternator. It's interesting that you still have an external regulator, most alternators incorporate the regulation of the DC current in with the built-in rectifier circuitry, that's why I didn't get into a lot of details in my previous post in an attempt to simplify the discussion. So does that mean that the output of the alternator does NOT go directly to the battery? If there is an external regulator then the feedback/charge current most flow through the regulator before returning to the battery. I guess that it's been awhile since I worked on an early alternator system, the modern systems all have a direct connection from the output to the battery, that's why a bad diode in the solid-state built-in rectifier/regulator inside the alternator will drain your battery when the car is not running, and fail to charge the battery when it is running. By the way, diodes ALWAYS short circuit first, with enough current they will burn up and open, but they always short out when they fail.

 

Yes,the output from the alternator runs through the regulator.

Since O'reilys computor did'nt go that far back they were having trouble as usual. The motor is actually a 69 truck motor. They said the system only went to 70 so I tell them give me one for a 70 Impala cause I figure they are the sam. The 70 did have the regulator built in so some time between 67 and 70 they got rid of the external regulator.


I think we have the short located. I will update later.

 

The output of the alternator should not run through the regualtor. The voltage regualtor should connect to the field terminal on the alternator. The VR controls the output of the alternator by varing current through the field coils, thereby varing the magentic field, and the output.

Don't diagnose problems at the parts store. Get a factory service manual, and trouble shoot as it tells you to. I'd open up the alternator and check each diode with a multimeter. Then check the field connections. Then, the voltage regualator. I would never fix an electrical problem without a multimeter and scematic. Dave