i have a 89 7.3L my batterys wont charge.my alt is good, new external regulater,new silinoid.and my batterys are good i can only start by geting a jump off my budys diesel,but once i shut my truck off i cant start it again. please help

 

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I think your Fusible Link (14GA-GRN) is open, it has a BLK/ORG (10GA) and YEL/WHT wires on one end and a RED wire on the other end.

 

thanks ill try that,anythig will help at this point

 

it worked thanx!!!!!!!!!!

 

FTE strikes again!!!

 

well back to the drawing bord . they eather drained off or there not charege ing

 

If you have a voltmeter, take a voltage reading on one of the batteries with the truck off, and then with the truck running. If the voltage is higher with the truck running(around 14 volts) then it is charging.

The next thing to do is check for a drain. Do the test below with a testlight. If it glows bright, then you do have a drain. Pull fuses and see if the drain goes away(make sure the domelight is off during this test). If you can't get the light to go out, then pull the wires off the alternator and see if it goes out.

 

That's a lot of power lost...

Have you read the batteries with a meter to see if it's still there but not getting out through the cables?

If they really are dead, the next thing I'd think about is what the heck is drawing power on the batteries with everything turned off.

Pull both negative connections, and read from the negative post on one of the batteries to the cable connection. If you read a full voltage draw (solid 12v going out) pull one fuse at a time from the panel until you don't see volts going out. DON'T put the fuses back in as you go, leave them out (important).

If the voltage drain stops, begin with the first fuse and reinsert all except the last one while watching the meter (this is in case there is more than one thing drawing power).

If pulling the fuses does NOT stop the voltage drain, look for things like the cigarette lighter that are "hot at all times".

Lighter sockets usually will corrode and cause a dead short in the bottom of them - if it looks bad pull the wire to it and insulate it from ground.

If any options (like foglights) have been added, check them too.

If there is any body damage, check wires in those areas.

That big a drain should have a very obvious cause once you find it...

Have your batteries checked too. Once the charge on a lead acid battery is totally wiped out, they can become shorted between cells. Many parts houses will test batteries for free if you bring them in.

 

Unless you have a very very cheap meter, this will not work. Most decent meters use very little current to work. This helps their accuracy, since they are actually draining some of the power away from the circuit they are testing.

Since they draw so little power, it takes very little to make them read. Most newer cars and trucks with digital radios and computer memories will have a little bit of normal draw. Most meters are going to pick this up and give you a full voltage false reading.

The reason the testlight works better is it takes more power for it to light. Most radio and computer memories will not light the testlight, and if they do, it will be very dim.

One other thing I need to start remembering is the newer trucks with the battery saver system. They will show a high drain till this system times out. So on these newer trucks, you should do the test for about 5 minutes or so to let the battery saver relay time out.

 

It works. But you have to make sure you are seeing full battery voltage on the "HIT(s)".

Going back through the other fuses is a follow up action. A 90 Stang I recently troubleshot had several circuits that drew anywhere from 6 to 10 volts until they were isolated. The meter was a Fluke.

I bet a test light would have made it quicker though.

I didn't know about that battery saver by the way - thanks for the alert.

 

one very important thing to check is the under hood light. it took me 3 weeks to find that the mercury switch went bad and the light was staying on, killing the batteries overnight.

another thing that comes to mind is to do an unhooked load test on the batteries. if you have 1 good and 1 bad or semi bad battery, the bad one will kill the good one overnight also.

 

thanx im going to try all your guys ideas. the help is great.