possible short?

[farriswheel]

Within the past couple of days, my alternator went bad. It wouldn't charge. I replaced it with a new one. My voltage is still very low, based on the dash meter. Sitting around 10v. It still starts up fine and everything. I hooked a dmm to it, and it read 12.6v or so, i revved it around 2000 for a minute and it went to 13v. Still with a new alternator, I figured it should be around 14v.

When I go to high beams, my lights just cut off. They turn back on when i switch it back. Would a short somewhere cause this, or could it be shorted itself?

 

[Brutis]

I went through similar issues with my 1990. First I learned that my headlight switch had melted, so I replaced it. I found out from previous post here on Oilburners that it will melt again if you don't separate the headlights from the system. If you're handy enough electrically you could rig you own system or do like I did and order a kit from LMC Truck for $40.00. Worked perfectly and I installed it in about ten minutes. That eliminated that problem. The issue I battled was the low voltage. I went through 3 70 amp alternators in about 6 months b/c they just don't hold up especially if you run any extra equipment like I do. A lot of guys switch over to a 130 amp alt, but I went to a 100amp alt because I found one cheap and it has held up fine, even running all the shop equipment and lights in my on-board workshop. Hope that helps some. I'm sure others will chime in with advice and part #s.

 

[farriswheel]

ahh ok. i guess ill try replacing it tomorrow

 

[typ4]

you need an adjustable voltage regulator to get it up to 14.2 volts. The dimmer switch being toast is most likely the headlight problem. They get filled with crap from being on the floor, oh and the connector likes to corrode and fail also.

 

[MIDNIGHT RIDER]

Do you have a 1G alternator and external regulator ??

My old half-a-million-mile 1G shows 14.8 at idle with no big draws turned on.

My regulator IS NOT adjustable, just plain jane.

It never goes below 13.8 or so with everything lit up.

Any old 12-volt battery should read 13.2-volts with engine OFF; 2.2-volts per cell.


Where are you checking alternator output ??

Check it at the HOT stud on the rear of the alternator, GROUNDing the meter at the alternator GROUND; this will give the true output of the alternator, regardless of any corroded connections or faulty wires.

 

[MIDNIGHT RIDER]

Is the replacement alternator brand-new or a rebuild ??

I often get a lot of bad rebuilds when dealing with the local mom-and-pop stores, sometimes going through three or four before getting a good one; this goes for alternators, starters, water-pumps, etc.

Sad as it is to say, I don't have near the trouble with the ones from the chain stores.

I think in an effort to keep their prices closer in line with the chain stores, the independents resort to cheaper/shoddier sources for their products.

 

[farriswheel]

i bought a 100 amp bn duralast from autozone. I went to orielly's and had them check if it was bad or not

 

[bike-maker]

The headlight switches in these things can and will short out.

The donor truck that I bought I got a screamin' deal on cause the headlight switch had shorted out.

The guy told me it must have shorted out just as he left it running out in the field

...............while he was lighting off his burn pile

The guy kept smelling something funky - coulda swore he didn't put any plastic in that burn pile. Then he turned around and saw his ol' faithful farm truck...................on fire

 

[farriswheel]

dang, thats no good at all. Would this be a reason why my voltage is low?

 

[farriswheel]

I replaced the switch. Really didn't help me voltage out any.

Engine turned off, it reads 12v, when i turn it on, goes down .3-.5 volts. So something is pulling. I unhooked all of my system, so it wouldnt interfere. Where should i start to fix this?

Thanks

 

[farriswheel]

maybe not even a short, or my alternator isnt charging. I replaced the regulator. Its 2v off, and goes to 11.7 or 11.8 when i turn it on. It was staying about 14 volts just the other day, idk what could be bad.

 

[MIDNIGHT RIDER]

maybe not even a short, or my alternator isnt charging. I replaced the regulator. Its 2v off, and goes to 11.7 or 11.8 when i turn it on. It was staying about 14 volts just the other day, idk what could be bad.

Okay, let's start at the beginning.

Were you having any of these issues prior to changing alternators ??

Are these issues the reason for swapping alternators ??

How good and what size are your batteries ??

Are ALL cables and connections in A-1 shape ??

To eliminate a bunch of possible shorts, you can pull most of the fuses.

 

[OLDBULL8]

There has been more alternators replaced than you can imagine because the battery/batteries are bad, in a dual battery system, one bad battery (shorted cell) will lead you to believe the alternator is defective.

Check each battery (disconnected). At the posts, each should read 12.48+ volts for a good battery when charged fully. Take the reading about 1/2 hr. after charging.

Does your system have an amp meter?
Does it have the idiot light?

Both systems have an electronic regulator, non adjustable on the 89 trucks.

Which OEM regulator do you have, the Gray or Black?
The Gray color one is for an amp meter system
The Black color one is for an idiot light system.
Do not use the electromechanical regulator in this system, the connector to the regulator will not index the wiring correctly.
The clear (not painted) regulator will work on either system.

Your headlamp switch incorporates a circuit breaker for the headlamps only, all other lights are fused.

If your headlamps go out when turned on, the switch is usually defective (circuit breaker) replace, can cause a fire.

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[MIDNIGHT RIDER]

Both systems have an electronic regulator, non adjustable on the 89 trucks.

Which OEM regulator do you have, the Gray or Black?
The Gray color one is for an amp meter system
The Black color one is for an idiot light system.
Do not use the electromechanical regulator in this system, the connector to the regulator will not index the wiring correctly.
The clear (not painted) regulator will work on either system.

That's pretty good for someone four-score and one; most that old that I know can't tell a single-tree from a cant-hook.


What year-models does that information apply ??

My 1985 with ammeter came with a silverish-zinc-colored regulator, as is the replacement that I put on there over twenty years ago.

Thanks.

 

[typ4]

When I go to high beams, my lights just cut off. They turn back on when i switch it back. Would a short somewhere cause this, or could it be shorted itself?

This indicates a possible dimmer switch problem.. You most likely dont have "shorts", a draw maybe. Transpo makes an adjustable VR for the 1G alternator
http://search.waiglobal.com/partnum.aspx?part=F540XHD.


I use them and they do wonders for low voltage problems. Make sure the regulator is grounded to the alternator case.