I need a mechanic

[Ole Farmerbuck]

I bought a 1990 1/2 ton chev 4x4 yesterday. Nice pickup. Put a new alternator on it and was showing charge just fine till i turned on the lights. Made it show discharge so i didnt think it was charging. I noticed the lights are bright so i hooked up a volt meter on the battery, It showed almost 15 volts. But with the lights on, the volt meter in the pickup shows only about 8 volts and the gas and oil pressure guages also start going down. All the time the v meter on the batt is showing about 15 volts. When i turn the sig light on, the inst lights dim everytime it blinks. Any help? Also, if i unhook the battery the moter starts slowing down. I know with the older alts we can run out irrigation engines without batteries. Maybe not with these later style alternaters?

 

[RaisedByWolves]

Buck, check your ground cables to the engine/frame.



.

 

[djohn]

I would suspect you have a cab grounding issue. The cab should be grounded to the chassis and I would bet either the ground cable is in bad shape and corroded or it is broken.

 

[reaperman]

Your battery must be connected for the truck to run properly, I'm surprised it stayed running at all. If you know for sure the battery isnt shot, I'd start looking at your voltage regulator.

 

[Ole Farmerbuck]

Ok thanks guys. I'll check the ground. The battery is good. Brand new and spins the motor good. Gotta make it work right, its my firewood truck.

 

[mayor]

I agree....bad ground!
You should have a flat braided piece of wire that will go from the engine too the firewall....maybe bolts onto the back of the head on the passenger side??? hmmm...cant remember for sure...but anyway....make sure that is hooked up and in good shape....if you cant find it.....then make one and hook the cab too the engine....also....make sure the ground cable has good connection too the engine!

If that dont work...take the chainsaw and rip all the stuff out from under the dash.....ya dont need all them fancy smancy lights anyway! hehehe.....let us know what ya find!

 

[GSP]

Check your ground.Try another volt meter just to see if yours is workin properly.

 

[Ole Farmerbuck]

My volt meter is actually a battery tester. One that you clamp on the battery and can flip switch to put a load on battery. I know the alt is charging cause i can unplug the alt and the headlights go dim and the motor starts pulling down. I dont think the motor should pull down for a while till the battery gets weak.

 

[GSP]

It's gotta be a bad ground connection.

 

[Ole Farmerbuck]

Just tossing this out there:

Do alternators need to be 'polarized'?

I think only generators do.

 

[Lurch2]

Fyi

In the age of computer controlled vehicles it's not a good idea to be unplugging/unhooking electrical components on a running engine. You can easily fry regulators, diodes, puters etc.. Even though it was effective troubleshooting for years it's a habit you need to break.

 

[SPED]

ground or cable corrosion

Be sure to check that your battery cables aren't really corroded either, sometimes it's underneath the rubber where you can't see. And defiinitely check those grounds, especially as posted above the one from the passenger side head to the firewall, that was snapped on my truck when i got it, I made my own thicker one for a couple bucks.

 

[grandpatractor]

Just tossing this out there:

Do alternators need to be 'polarized'?

Alternators-No
Generators-yes

 

[grandpatractor]

In the age of computer controlled vehicles it's not a good idea to be unplugging/unhooking electrical components on a running engine. You can easily fry regulators, diodes, puters etc.. Even though it was effective troubleshooting for years it's a habit you need to break.

Yup, what he said:monkey:

 

[user 19670]

You 'DID' disconnect the battery when you changed out the alternator didn't you?

 

[Ole Farmerbuck]

I dont care what anyone else says............you guys are alright!!! lol lol WE fixed it. I ran a ground wire from the firewall to the motor and sure enough, it works. Thats great! Party at RBW's for all who helped! BYOB

 

[Ole Farmerbuck]

You 'DID' disconnect the battery when you changed out the alternator didn't you?

Uh....no i didnt but never have. Prob should though. Thanks

 

[Ole Farmerbuck]

I agree....bad ground!
You should have a flat braided piece of wire that will go from the engine too the firewall....maybe bolts onto the back of the head on the passenger side??? hmmm...cant remember for sure...but anyway....make sure that is hooked up and in good shape....if you cant find it.....then make one and hook the cab too the engine....also....make sure the ground cable has good connection too the engine!

If that dont work...take the chainsaw and rip all the stuff out from under the dash.....ya dont need all them fancy smancy lights anyway! hehehe.....let us know what ya find!

Chainsaw to the interior? Wow! I cant do that, like i said, this my firewood truck. Maybe my new pickup but not the firewood truck!! lol But you were right, bad ground from motor to firewall. Thanks

 

[ShoerFast]

Few year ago I had worked for a propane company that was owned by a true 'Rocket Scientist' . The owner worked with NASA after one of the Titans shelled apart just after it left the launce pad. (maybe you remember the news clips of a huge fire ball?) That rocket exploded due to electrical grounds. This is going some where,,,,,

Working as Maintance Manager on his trucks, everything he had ran on propane, and everything was computerized to monitor the propane it burnt, cool stuff! But if the grounds and wires were not heavy enough there were problems, dirty electric Robert called it.

Working with ol-Robert, it did not take long to learn how to wire his equipment, if you read the chart for wire gauge requirements, and doubled it, you were on his team. Especially if you added extra ground-wires.

To this day everything I run has quicker battery recovery, brighter lights and more constant electrical operations just by running heaver wire then it came with. It is really nice to have hi-beam lighting on low-beam and killer hi-beams, or heater motors that push you back in the seat. (well that might be a stretch)

Moral of the story, wires and grounds can never be to thick.

 

[djohn]

Secret about unhooking your battery when working on your electrical system. If you unhook the ground side the battery is isolated and unless you are really accident prone you won't arc your wrench. Much easier to unhook the ground and not have to worry about handling a "hot" wrench that might hit the fender or some other grounded part.

Also, take your rings off if working on the electrical system and you didn't unhook the battery. Bad things can happen to your wedding ring if you get in the wrong spot.