The charge light stay on when the truck is running. 1978 hilux 20R

A few months ago the charge light would come on very dim when I had the heads lights on, not always just once in a while. Then one night I saw the light come on after I slammed the door shut, it stayed on for a minutes then went out. After that my batteries started to smell like rotten eggs, went through 2 batteries in 4 months. Then the head lights started going out one by one, drove around with the high beams on for 2 more months. Took it to a mechanic and he said the voltage regulator needs replacing. I replaced it with this one. Now the charge light stays on all the time. All the ground wires are brand new just replace them. Do you guys have any ideas to why this is happening?

 

A new update. The charge light goes out after truck starts. Drove around for a few miles then the truck died at the light. It starts up again easily but with out rpm it dies, and there is a buzzing sound coming out from the charge light.

 

Alternator.
pull it and check it at a parts store.
Or crank the truck and put a voltmeter on the battery. Should be 13v DC or greater while engines running.
if its not charging the battery and the parts ppl tell you alternators good, start looking for loose or damaged wiring. Maybe bad ground somewhere.

 

Could be a bad regulator too. Idk that brand. Should be a simple way to test it.

 

The door slam sounds like bad connection somewhere. Like you jiggled something loose

 

Electrical stuff can be intimidating. Get a multimeter if you dont have one and use it. The fsm has all the tests you need. Its logic and common sense. Test and use proccess of elimination and you find the problem.

 

Does any on have a diagram of the voltage regulator?

 

The SMP brand voltage regulator is very good quality and shouldn't be am issue. The part number is correct for the '78.
How is the belt tension on the Alt? Tight enough it should have about 1/4" to 1/2" of deflection with finger pressure on the belt. What's the condition of the belt?
Check the connections on the alternator (including the spade tabs in the connector) to be sure they are clean and tight.
Check battery voltage when the truck is running AT IDLE to see what kind of output you are getting from the Alt. It should be at least 13.5 volts to 15 volts max. Lower than 13.5 volts the Alt needs replacing, higher than 15 volts it's overcharging.
What type & size battery do you have in the truck? How old is the battery? Has the battery been jump started before & how many times?
Correct size group should be 24F. CCA (Cold Cranking Amps) Rating should be 710 to 800. Check the battery label. Having the wrong size or rated battery can cause charging problems.
Any battery over 3 years old can be suspect and should be load tested. Jump starting a battery can cause internal damage to the battery, which can also cause charging problems. Again the best way to know if this is happening is a load test. Any decent parts store can do this for free.

Otherwise, I agree with swampedout, pull the alternator & have it tested at a parts store (maybe at the same time you get the battery tested). If all your connections are good, it's more than likely it's the cause. It probably has some broken wires in it so it's not generating or sending charging voltage out.
If the Alt is more than 10 years old or if you don't know how old it is, it's worth testing it.

The voltage regulator is the old style mechanical with relays inside; they usually don't just immediately blow up, even if the Alt is bad. Test all the things I mentioned above before you go digging around in the Voltage Regulator wiring.

 

I had the same problem on my 81. The charge light would come on and stay on, (not all the time) some times it would work just fine. Other times it would stay on, then go out as I was driving. When the charge light would go out it made a sound like a relay clicking. What I did was clean all the under dash fuses. That seems to have worked, I haven't had the problem for a couple of weeks now. I don't know what's up with the fuses. Sometimes theheadlights wouldn't come on, and I'd clean the headlight fuses and they would work fine. My wiring harness is in good shape, it hasn't been butchered.

 

I think I have found my corporate. Apparently the previous owner created this little harness to attach to the alternator. The green attachment does not match with the alternator connection so the previous owner got connectors that matched the alternator and the harness, then ran wires between them. But did not secure the Toyota harness to the frame or body, it just hangs there and bouncing around. That would explain, why when I slam the door the charge light would come on. The wires to this harness are completely dry rotten and full of dirt and grime. He also used a different gauge of wires then the ones comping out of the Toyota harness. So I have 2 option I can recreate the make shift harness with the right wires and connected back up and make a bracket for the Toyota harness to keep it from bouncing around. Or switch the green harness to match the alternator connection. I want to pull out the crimps from the Toyota connection and install them in the connection that matches the alternator.

 

Well, I did say the terminals needed to be cleaned. Psychic mechanic strikes again.

Got a source for new plugs with terminals if you want to wire in a new one: http://www.globalsoftware-inc.com/co...Connectors.htm

Should be item 2 on that page.

 

@13Swords Thanks for the website I did not know about that. In the mean time I need something temporally to be able to drive the truck.

I forgot to mention that when I changed the voltage regulator I took apart the old one and one of the copper wires burned up inside and snapped. I wish I would of taken a picture of it.

 

No problem. I never got around to getting one of those replacement Alt plugs myself for my truck. My old plug was broken & unsalvagable so I cut it off & just put spade lugs on the end of each wire, then plugged them individually onto the lugs on the Alt in the correct locations for each wire. Been driving it this way for over 2 years with no problems.

 

I was thinking of doing the same thing.

 

I connected the wires to the back of the alternator to get it running again. Testing the terminal at the battery with the engine running I get 12.25 V, doing the same test with engine off I get 12.34 V.

Also I have another question. Could the voltage regular have something to do with the battery not being charged? My original one got burned out like I mentioned before replaced it with a new one. Just asking I would hate to go through all the trouble of taking off the alternator for no reason.

 

With engine running 12.25 volts is still not in spec & shows the Alt is not charging. Take the Alt off the truck & go get it tested. It's only two bolts. Git her done.

The voltage regulator can have something to do with the battery not being charged, but in your case I seriously doubt it. You said you installed a brand new SMP brand regulator so it should be fine. Get the Alt tested. Even if you find out it's bad, new ones don't cost that much.

 

Taking the alternator out is not hard. Youll need abt two wrenches and one beer.

 

You are right about that @swampedout . I ended up having the rest cause I'm having the same problem, new alternator and belt same old problem. Truck shuts off after about 10 mins of running at normal rpms, and i'm getting 12.25V at the battery with the engine running and 12.35V with the engine off. Also checked the back of the alternator at the external bolt is the only live wire and I was getting 12.25V out of there.