I have issues. Can you help??

[notajeep]

Electrical issues that is.

On the fourth of July, after the fire works, coming home in the dark on the trail, my light dimmed and eventualy the truck died.
So... I replaced the alternator, and the voltage regulator. It ran fine, however the charge light on the dash stayed on since.

Now, last night, went wheeling again after dark, turned on the lights, and again they got dim and drained the battery.

Today, I jumped the truck and it runs fine, with the lights off, but is only charging at 10.5 volts. When I turn the light on with the truck running the battery voltage drops rapidly. If I turn the lights off, the battery will begin to charge again.

So, I know that somewhere I have a short with the lights, but my real question is, Which is bad, the alternator or the regulatgor? Is there a way to check either? If I have lights running dirrectly off the battery, does that give you any indication of where the short might be?

My truck is a 80 toyota with a 20r and an external voltage regulator.

Anybody?

 

[bobdog]

Today, I jumped the truck and it runs fine, with the lights off, but is only charging at 10.5 volts.

If it is only putting out 10.5 volts with the lights off, the problem is not the lights. It is the alternator, voltage regulator, battery or the way it is wired.

 

[notajeep]

Nothing has changed with the wiring. I am just not sure if it is the reg or the alt? Which came first?

 

[richpblaze]

Throw an OHM meter

On the battery is the voltage isn't rising with the motor running, it will be your alternator.

 

[timpanogos]

Dan, stop by most any auto parts store, they will have a gizzmo that they can hook up and it will tell you if the alt/batt/reg is bad

 

[waynehartwig]

Dan, stop by most any auto parts store, they will have a gizzmo that they can hook up and it will tell you if the alt/batt/reg is bad

Bingo! It's a cool deal too.. Tell you if it's the diodes or etc bad in the alt, too.. Not just 'bad alt'.

If it's charging, you should see ~14 volts across the battery with the motor running. If you aren't, then you have something wrong. It could be anything from a loose/coroded wire to bad parts.

There is a way to jumper the regulator to make the alternator charge, I just don't remember which pins to short. Basically what you are trying to do is put 12v to the field? so it will excite and put out a charge. Again, someone might know this as I don't remember (it's been 20? years since I've done it).

But I'd do the Checker/Autozone thing and not mess with it ...Of course after I checked over the wiring

 

[91MJ97TJ]

Bingo! It's a cool deal too.. Tell you if it's the diodes or etc bad in the alt, too.. Not just 'bad alt'.

If it's charging, you should see ~14 volts across the battery with the motor running. If you aren't, then you have something wrong. It could be anything from a loose/coroded wire to bad parts.

There is a way to jumper the regulator to make the alternator charge, I just don't remember which pins to short. Basically what you are trying to do is put 12v to the field? so it will excite and put out a charge. Again, someone might know this as I don't remember (it's been 20? years since I've done it).

But I'd do the Checker/Autozone thing and not mess with it ...Of course after I checked over the wiring

Hey can they tell any shorts? Or is it just those sort of things because I think I have a short going back to the Rear Windshield wipers on my hardtop or the switch is bad.

 

[timpanogos]

it'll be something easy (not neccessarly cheap) ... battery or something ... trust the gizzmo

 

[Rot Box]

Dan, I'll bet that it's just your (now less than 60HP) engine. It's just too worn out to power everything all at once...

Agreed with having the truck tested. Also I had this problem before, and (like stated above) it was as simple as a bad connection mine being the battery terminal. So it is best to go through ALL connections expecially in the fuse box...
I can swing by and lend a hand if your going to be around in the mornings

 

[jet_aj]

i've seen where wires going to the alt were shorted together, (external regulater) causing a short... I replaced 2 alts that were not bad because of it! so check your wires/connections for any corrosion or missing insulation. you can check for a short to ground by using a test light (THIS IS THE ONLY TIME I EVER WOULD SAY TO USE A TEST LIGHT OVER A DVOM (test meter)) What you do is take the positive battery lead off the bat and hook the test meter in line (bat post---light---bat cable) if everything is off and your doors are closed and hood light is removed, if you have one, you should not have any power draw. (maybe the radio or clock, so removed the fuses for them) if it is on then you can remove one fuse at a time until the light goes off. then you will know what circuit the short is on. If it is your headlight circuit, dont rule out the headlight switch (i've had to replace them before because of a short). just Follow a wiring diagram to find where the short can be.
If you remove all the fuses and the test light stays on, then it will be on the side between the battery and the fuse panel (alternator/reg, wire going to fuse panel, offroad lights you may have installed, ect...)
If its not the alternator or regulator you'll have to play 'Chase the Wires' which could take hours or days until you find the problem. Electrical gremlins can play anywhere in your truck and it can be a headache until you kill the little sucker! GOOD LUCK!

 

[waynehartwig]

Hey can they tell any shorts? Or is it just those sort of things because I think I have a short going back to the Rear Windshield wipers on my hardtop or the switch is bad.

DOn't think so.. .Think you have to deal with that on your own

 

[Paul R]

You can check for a short to ground by using a test light (THIS IS THE ONLY TIME I EVER WOULD SAY TO USE A TEST LIGHT OVER A DVOM (test meter))

Just curious as to why you prefer a light instead of meter? I have done this with a meter before and I just looked at amp draw... I thought it was helpful to see the load being drawn ie. it was easy to see the stereo was a tiny draw... Is it because the light is more visual? I definately agree that that is the step to take I thought I had a short in my truck and I went through this pulling the fuses and figured it all out eventually. The PO had hooked up and amp or something in it and there was a pretty thick wire that would short to ground under the carpet. I fixed that and replaced the battery and it has been all good ever since...

 

[crawler12]

I don't know if it would be of much help but I do have a spare toyota Alt. I believe it's from a 20R, not even sure how good it is though i'm pretty sure it works. You're more than welcome to it if you think it would help. It would be a good excuse to get you to come check out the M.U.T.T.

 

[notajeep]

I don't know if it would be of much help but I do have a spare toyota Alt. I believe it's from a 20R, not even sure how good it is though i'm pretty sure it works. You're more than welcome to it if you think it would help. It would be a good excuse to get you to come check out the M.U.T.T.

Who needs an excuse??

Update:
I have now replaced the second alt and voltage regulator and got a brand new optima red top battery. It is now charging at 12.3 volts and climes SLOWLY with the motor running. The charge light on the dash is still on.
I know I have a short some where in the lights, but I still cant figure out why it will not charge to 13+ volts with the lights off. This truck does not have a fuse for the lights (that I can find) so I guess that there could be some sort of power draw even with the lights off that could be keeping it from fully charging???

 

[jet_aj]

Just curious as to why you prefer a light instead of meter?

Just because if you are under the dash pulling fuses its easier to see the light rather than having to keep walking back up to the meter to check it... Also, Most meters only have a 10Amp fuse on the amp circuit, if your short is bad enough it could draw more than that. Or if you by chance turn on your headlights for some reason, they will draw more than 10 amps and pop the fuse. I hate blowing fuses in meters

 

[jet_aj]

Who needs an excuse??

Update:
.... The charge light on the dash is still on.
I know I have a short some where in the lights, but I still cant figure out why it will not charge to 13+ volts with the lights off. .....

I'm not sure on the toyota, but on some of the older fords/chryslers (70's/ early 80's) they actually used the "Alt" light on the dash to sense the battery voltage and used that for exciting the alternator... If you have a burned out light, it wont charge at all. Or you may have a bad ground on the dash, between the engine and chassis, ect... CHECK YOU BOOK FOR THE CIRCUIT THAT ALT USES FOR REGULATING, or remove the light in the dash and see if that affects your alternator output.
If you dont have a good ground strap in between the engine and chassis you can end up will all sorts of electrical gremlins, and can end up with electrolisis (spelling?) in your coolant system causing corrosion/rust in the coolant passages in the engine... What happens is your engine will ground through the coolant/water and radiator... which is not good.
If it doesn't use the "Alt" light for sensing batt voltage, then It may be a wire is partially broke/corroded connection or whatever on the wire going from the Alt to the Regulator that is used for exciting the alt. What you can do is actually take the Excite wire (Usually the 'I' terminal on an alternator i believe) and hook it to the + (positive) side of the battery, what that does is bypass the regulator. DONT keep it connected too long or you can damage it. Just have your meter connected to you battery so you can watch the voltage easily. What the alternator does is sense the battery voltage and output according to what it needs. Should still be near/above 13~14 volts.
Again, First check ground straps/ electrical connection on the Alt/Reg circuit. Most times on older vehicles its just a matter of corroded connections, pinched or broken wires...

If you can't remove a fuse/ect from the light circuit and you still see a short to ground with the lights off it could be a bad headlight switch, corroded wire, or even a wire that has the insulation wore off and shorting, like at a spot where the wires go through the firewall into the cab. <--- that right there is a big possibility
Again, good luck!

 

[toytrucks79]

how many volts are you getting going in to the alt? you should have 12 volts if the key is on if you are not getting 12 volts to the alt it will not put out as much!

just a thought\\\and on the meter over the test light, when you pay $450.00 for a good meter you dont want to risk blowing the internal fuse. then you have to get it fixed.
(this has happened to me) the meter was a matco.