77 Dat 620 Charge Light on

[Suspect]

Last night I was driving the 77 620 and a tiny hose blew by the alternator. It took me 3 gallons of coolant to go 40 miles to get home. Within 5 miles from my house, the charge light came one and its not charging. If you unplug the plastic connector on the back of the alternator, the motor starts speeding up slightly and when you plug it in, its slows down. This usually means the alternator is good. The voltage regulator is nearly new. I've had the light come on before and my dad was moving the wires around and the light went back out.

 

I'm fairly confident its a wire, does anyone have any ideas on which wires I should be looking at?

[Guest kamakazi620]

The 2 wire plug on the top play with those make sure the connecters are tight,mine was loose and i had to use needle nose pliers to tighten them up heres a pic of how P/O fixed it

when the tape got old the plug would come undone and the dash light would come on i tightened the connectors and shes been workin ever since

[620blues]

The 2 wire plug on the top play with those make sure the connecters are tight,mine was loose and i had to use needle nose pliers to tighten them up heres a pic of how P/O fixed it

when the tape got old the plug would come undone and the dash light would come on i tightened the connectors and shes been workin ever since

 

I had the exact problem in my 77, Kamikaze is right, loose wire on mine too, Well, melted actually. I had to snip the wire and reconnect ...That was AFTER changing out the alternator and regulator twice!:angry:

[Guest kamakazi620]

I had the exact problem in my 77, Kamikaze is right, loose wire on mine too, Well, melted actually. I had to snip the wire and reconnect ...That was AFTER changing out the alternator and regulator twice!:angry:

I won't be right until my advice fixes it.................. :P

[Suspect]

Well I spent a some time messing with it. My past experience, the belt is usually loose and causing it not to charge enough. This is not the case this time. Also the wiring on the alternator is tight and looks good. I narrowed it down to a wire on the regulator that goes to the inside of the truck. It must something connection wise in the plug directly from the voltage regulator. Right now after messing with wires, checking connections and someone's repairs.... I'm hitting 13.4V on idle with nothing one and with the high beams on and heater blower max, 11.8V. The charge light is still on.

 

Moving the wiring around must have done something because last night I let it run with the lights on and the battery went dead.

[datzenmike]

Well I spent a some time messing with it. My past experience, the belt is usually loose and causing it not to charge enough. This is not the case this time. Also the wiring on the alternator is tight and looks good. I narrowed it down to a wire on the regulator that goes to the inside of the truck. It must something connection wise in the plug directly from the voltage regulator. Right now after messing with wires, checking connections and someone's repairs.... I'm hitting 13.4V on idle with nothing one and with the high beams on and heater blower max, 11.8V. The charge light is still on.

 

Moving the wiring around must have done something because last night I let it run with the lights on and the battery went dead.

 

 

11.8 v at idle with heater and lights on???? What does it measure if revved up????

13.4 v at idle but what does it read revved up?????

 

Everything sounds ok. Idle has very low output anyway. Try the measurements revved up a bit.

 

I've had water get in the alt. and the light comes on because it gets on the brushes. The longest it stayed on was an hour or so until it dried off.

[Suspect]

I just went out and did a voltage test again. I got 12.5 revved up and it dipped below 12.0 on idle with heater blower running. With nothing running, hit 13V on rev and 12.3 on idle. My idle is about 1000 to 1100rpm. The charge light is still on. It seems to be charging right but why is the light still on?

[datzenmike]

I just went out and did a voltage test again. I got 12.5 revved up and it dipped below 12.0 on idle with heater blower running. With nothing running, hit 13V on rev and 12.3 on idle. My idle is about 1000 to 1100rpm. The charge light is still on. It seems to be charging right but why is the light still on?

 

Proper charge should be 14+ volts when revved.

[Suspect]

Thats what I was thinking. I've had issues with dim lights, and ground issues before. When I first got the truck, it didn't charge at all. I found out that someone put the two wires on the alternator backwards, but then removed the wire that was shorting. I fixed that and the throttle cable started smoking and froze up. I added a better ground, replaced the throttle cable and I had real nice bright lights. About a month later, my battery smelled like an open septic tank. I checked the voltage and it was in the 18V +. I replaced the voltage regulator and the voltage has been low ever since but its been reliably charging. When I hit the brakes the headlights will dim, signals are also noticeable too.

[datzenmike]

Borrow a battery and see if anything changes. Have the alt tested too. After reading that I would be worried that the battery or alt is cooked.

[Suspect]

I swapped the battery because it was weak... but the voltages I gave you were with the better battery. I decided to swap the alternator. Now I'm hitting 13.7 on fast idle with nothing on, and 13.6 with lights and heater blower on. I think its all good now.

 

Thanks everyone for the help.