Alternator charging issue

dcdoug · #1 (**permalink**) 09-07-2015, 06:01 PM

I have a battery charging issue that I'm struggling to fix.

A bit of background, because this has been a complicated issue:

First, I had problems with the car starting (out of the blue, not because I made any changes). The solenoid tested bad and was replaced. Then the ignition switch stayed in the "on" position and ran down the battery and that was replaced. Then the start circuit seemed to work, but the battery stopped charging. I will say that right before all of this happened, I briefly saw a weird "ticking" of the ammeter while it was showing charge (while driving), but the needle would tick back to the middle neutral position. I haven't seen that before. Next day, car wouldn't start and the above happened.

It feels like I must have a loose wire somewhere, but I've checked all the obvious ones and they are tight. The car starts fine, but the ampmeter shows discharge when it's running and the fans are on. I have confirmed with a multimeter at the battery that the battery is not being charged.

I have had the alternator tested and it's good. I replaced the voltage regulator. I checked connections under the dash and they seem tight (I tightened a few). I did not remove the dash, but crawled under it, so it wasn't a thorough inspection as space is tight and I could have missed something.

The only other clue I have is that when the starting problem went away and changed to a charging issue, the "on" ignition light stopped working, which seems to also be referred to as the "alternator problem" light. The bulb visually appears Ok, but I have ordered a replacement. The wiring diagram shows that the other side of this connection is the "I" terminal on the voltage regulator. I find it hard to believe that a bad bulb would be a cause of this problem and is more likely a symptom. I can say that with the bulb installed, there is no continuity between the two leads going to the bulb and it seems like there should be.

Thoughts?

Weekendwrench · #2 (**permalink**) 09-07-2015, 06:56 PM

Very difficult to be of much help without being there, but te only two things I can think of is to check for good engine ground to chassis or I have had battery's show 12V but have no amps. Good luck

patrickt · #3 (**permalink**) 09-07-2015, 07:09 PM

Quote:

Originally Posted by dcdoug

Thoughts?

The "idiot light" also functions to excite the voltage regulator. If the itsy bitsy filament in that light burns out, your alternator will not charge.

patrickt · #4 (**permalink**) 09-07-2015, 07:28 PM

From my automotive shop textbook, circa 1974...

Large Arbor · #5 (**permalink**) 09-07-2015, 07:51 PM

I sort of went through the same thing. I had a bad cell in a brand new Optima battery. First it was a bad VR. Then became a bad battery.

Phil

Archrms · #6 (**permalink**) 09-07-2015, 08:10 PM

Check the wire between the alternator and the voltage regulator. Run a temporary jumper wire between the two to see if it eliminates the bad signal. A faulty wire in mine kept telling the system to charge the battery, resulting in a couple of fried batteries before it was figured out.

dcdoug · #7 (**permalink**) 09-07-2015, 08:18 PM

Quote:

Originally Posted by Large Arbor

I sort of went through the same thing. I had a bad cell in a brand new Optima battery. First it was a bad VR. Then became a bad battery.

Phil

I replaced my Optima's as part of this goose chase, so that's not it either.

dcdoug · #8 (**permalink**) 09-07-2015, 08:26 PM

Quote:

Originally Posted by patrickt

The "idiot light" also functions to excite the voltage regulator. If the itsy bitsy filament in that light burns out, your alternator will not charge.

I was worried this might be the case and I'm thinking this might be it (sort of a dumb design). Here's my guess as to what happened:

Loose wire behind the dash (there were several I tightened, but none were super loose other than one of the leads to the panel lights dimmer knob), caused some of the other failures (solenoid, ignition switch, voltage regulator and ignition idiot light) and I'm hoping when I replace the bulb (all the filaments look good, but hopefully it's bad) it will all work.

dcdoug · #9 (**permalink**) 09-07-2015, 08:28 PM

Quote:

Originally Posted by Weekendwrench

Very difficult to be of much help without being there, but te only two things I can think of is to check for good engine ground to chassis or I have had battery's show 12V but have no amps. Good luck

All my main grounds are tight and have been double checked.

patrickt · #10 (**permalink**) 09-07-2015, 08:41 PM

Quote:

Originally Posted by dcdoug

I was worried this might be the case and I'm thinking this might be it (sort of a dumb design). Here's my guess as to what happened:

Loose wire behind the dash (there were several I tightened, but none were super loose other than one of the leads to the panel lights dimmer knob), caused some of the other failures (solenoid, ignition switch, voltage regulator and ignition idiot light) and I'm hoping when I replace the bulb (all the filaments look good, but hopefully it's bad) it will all work.

The electrical design is really, really simple. One side of the light is fed off the ignition switch, the other side of the light runs to the voltage regulator. If the system is not charging, the connection at the VR will be grounded, and as soon as the system starts charging, that ground becomes 12v positive. That's why when you turn your key on, but don't start the car, the light is on, but goes off as soon as the charging begins. If you turn the key on, and the light does not come on, then something is wrong on the circuit.

dcdoug · #11 (**permalink**) 09-08-2015, 06:42 AM

Hopefully it is the bulb (even though the filament does not appear to be broken). I'll know on Wed.

dcdoug · #12 (**permalink**) 09-10-2015, 11:31 AM

The ignition light bulb was the final problem (even though visually it appears fine). Replaced it and now the system charges.

Thanks Pat.

dcdoug · #13 (**permalink**) 09-11-2015, 07:51 AM

So if I wanted to wire a resistor in parallel with the ignition bulb circuit as a back up in case the bulb burns out, what ohm rating should the resistor be? I've seen 560 ohms referenced elsewhere. Sound right?

patrickt · #14 (**permalink**) 09-11-2015, 09:35 AM

Quote:

Originally Posted by dcdoug

So if I wanted to wire a resistor in parallel with the ignition bulb circuit as a back up in case the bulb burns out, what ohm rating should the resistor be? I've seen 560 ohms referenced elsewhere. Sound right?

No. You want a 15 ohm resistor. Now, at 14 volts a 15 ohm load will draw a little under one amp and make a little under 14 watts. So, order a 15 ohm, 20 watt resistor off Amazon. Here:
[ame="http://www.amazon.com/Watt-15R-Wirewound-Cement-Resistors/dp/B0087ZDBW4"]2x 20 Watt 15R Wirewound Cement Resistors 20W 15 Ohm 5%: Single Resistors: Amazon.com: Industrial & Scientific@@AMEPARAM@@http://ecx.images-amazon.com/images/I/311j04URzIL.@@AMEPARAM@@311j04URzIL[/ame]
You don't have to wire it directly around your alternator light, unless it's convenient to do so. All you have to do is route it to the voltage regulator and the ignition switch just like the light is wired. You can test it, of course, by disconnecting your alternator light and running your car. If you're getting over 13 volts then you know it worked.

dcdoug · #15 (**permalink**) 09-11-2015, 12:20 PM

Cool. Thanks Pat.

dcdoug · #16 (**permalink**) 09-13-2015, 07:32 AM

So after getting some push back over on CACC from others saying this resistor was too big, I measured the existing circuit, which is 10 ohms.

patrickt · #17 (**permalink**) 09-13-2015, 04:38 PM

Quote:

Originally Posted by dcdoug

So after getting some push back over on CACC from others saying this resistor was too big, I measured the existing circuit, which is 10 ohms.

I tried to clear it up with a pic from the old Ford literature. The problem is that we're still using 1965 technology and a lot of guys are thinking "modern" wiring.