I want to unplug my alternator and drive a short distance to determine if it is making a non-mechanical whistling sound (magnetic interference). Can I unplug it and drive a short distance or will that damage the computer and electronics?

 

No, but your battery won't like you...

Adrianspeeder

 

Does that mean yes I can safely drive with it unplugged?

 

A short distance, like around the block, yes.

 

Your alternator supplies all the juice to your truck while it's running (computer, ignition, stereo, lights) which can draw quite some amperage (I have a '97 and it's 90 amps for stock alternator and 130 amps for towing package). Your battery is for light loads and for turning the starter to crank the engine over and start it up. Depending on how strong/new your battery is will decide how long it will last. I would even feel uncomfortable driving around the block with only battery power. If you do, definitely don't go outside walking distance from your house and make sure there's plenty of room on the side for you to pull over when it dies.

 

Actually, I would bet that it isn't quite as bad as some are making out here. If you have a strong battery to begin with, and minimize your use of accessories such as lights, stereo, etc, I would bet you could drive 20 to 50 miles on just the battery.

Back in the old days, I personally knew of a car (1979 Chevette) that went nearly 200 miles with the alternator unplugged. Now, I doubt that you could go that far today, what with computer controlled engines, electric fuel pumps, and whatnot, but I bet you can go farther than just around the block.

Just my two cents...

 

Haven't had to do it with my 150, but both my old 90 Tempo and my wife's 98 Contour got about 50 miles with the alternator off line before the battery died completely.

A short distance won't hurt anything.

Steve

 

Indeed, it's called the reserve capacity of the battery, and it's measured in amp-hours or millamp-hours depending on teh size of the battery. Without the alternator to charge it, the engine will be drawing all its power from the battery. You should be fine for around-the-block, no problem.

-Joe

 

If you are just trying to determine if the altenator is charging, why not just remove the battery after you start the vehicle. If the altenator is charging, it will run fine, if it is not, the engine will die. I used to do this all the time years ago. There may be some reason for not doing it on the new systems, but I can not see think of one. Anyone know of a reason?

 

He's not trying to determine if it's charging, he's trying to determine if it's the source of some electrical interference (based on my read of the original post.)

-Joe

 

Thanks, I missed that.

 

NEVER, on a modern computer controlled engine, try to run on the alternator alone, intentionaly.
There becomes no regulation of system voltage.
The alternator doesnot regulate it'self in the absence of a battry sink load.

 

I appreciate the reply. I thought that the computers might be a problem.

 

I don't think it would work anyway. On modern computer-controlled, fuel injected, electric fuel-pumped vehicles, the battery is an integral part of the circuit, unlike the old days when the battery's main job was to start the engine. I think that you could view it like this - all systems actually run off the battery, and the alternators main task is to keep the battery charged. I don't think a modern vehicle will run at all without the battery, and in fact I'll bet a modern vehicle won't even run with a completely stone-cold dead battery in it.

 

I'm not so sure.... Simple way to find out though: Start the engine and pull the battery cable. I suspect it'll keep on running.

But as for the original question, yes, the battery will feed the truck while the alternator is unplugged.

For the record, should the alternator ever take a dive, turn off all unnecessary accessories.... blower, radio, lights, etc to maximize the distance you can travel on the reserve capacity of the battery alone.

Around the block, you'll be fine.

-Joe