View Full Version : ING Light on, Volts Dropping

11-18-2006, 12:54 PM
First, I know I have been asking a lot of questions lately, and for that I apologize! I hope I am not being to much of a pest. It just seems that as soon as I fix one issue, another pops up.

On to the issue:

Replacing the water valve last week, I found some time to refill the radiator, and burp it today... so I filled her up, and stuck a rag over the open fill hole to catch any fluid when it burped.

Turn the engine over, and see that the ING light is staying lit. I also watch as the voltmeter slowly drops from it's usual 15... to 14... to 13... to 12... I cut off the engine, and checked connections at the coil, alternator, etc... Looks good.

Turned the car back on... amps started at 12... dropped to 11 and continued to slowly drop, so I shut her off.

Reving the car didn't seem to change anything.

So... do I need a new alternator? Battery? Anything else I should be looking at? Replace the batter first, then move to the alternator?


11-18-2006, 01:14 PM
Go to your local generator shop and buy a new voltage regulator. It is found inside the plastic cover of the alternator. A little smaller than a pocket sized tape measure. Easy to remove with a small screw driver.
Buy two, they are not always dependable.

11-18-2006, 01:44 PM
I would check the battery first by disconnecting the positive and negative leads. SLOW charge the battery to get it back up to 13.5 - 14 volts. Then test battery with a load test or check each cell with a hydrometer. If battery proves OK then your problem is either a ground short (which will need to be traced out by isolating circuits) or the alternator (did it get wet?). I have to go so hopefully someone will jump in and finish circuit trouble shooting if need be.

11-18-2006, 03:10 PM
If your ignition light is staying on while the engine is running, that means that the alternator is putting out LESS voltage then what is in the battery. In other words, the alternator is not charging.

Since you were doing work on the radiator, which is close to the alternator drive belt, perhaps you spilled some coolant onto the belt and it is slipping. I would check that out first. If that checks out OK, then it's time to have the alternator checked. Most parts houses will do that for you. Or, better yet, find a local electrical rebuilder and bring it there.

11-18-2006, 06:23 PM
I guess this will sound like a dumb question to all you old timers, but I'm just beginning to learn. Is the ignition light supposed to go out on a TR3 also once the engine turns over? Mine is always on once I turn the key, whether the engine is running or not.


11-18-2006, 06:53 PM
The alt did indeed get wet when the water valve blew.

I will check the belt to make sure it has no coolant on it.

The battery is maint free, so there are no cells to check.

I did find a loose connection on the alt solenoid and pushed it back on tight. Voltage stopped dropping, and with some revving, came up to 12.5 volts. So I have some progress, but still have an issue (ING light is also still on).

So I am less inclined to believe it's battery. Though perhaps I will buy a trickle charger and see if that makes a difference.


11-18-2006, 08:02 PM
As others have mentioned, most parts stores will bench test an alternator for you and the ones I deal with don't charge for it. If you have a volt meter, check the battery voltage with the ignition off and then again with the engine running. A typically battery will have a voltage of about 12.5-13v (with the engine off). The alternator will run about 1 to 1.5 volts higher than that so it can charge the battery (look for 14-14.5 volts with the engine running). I don't particularly like Smiths volt gauges if that's what you've got in the car. They have a very slow response time.

Regarding the TR3, it uses a control box and generator instead of an alternator but its charge warning light should go out just like cars with an alternator. I've never been able to adjust the generator control boxes but there have been a couple of threads on this board which have talked about how to service and adjust them.

11-19-2006, 12:18 AM
It is an original Smiths meter.

I do have a VOM, but I am embarrassed to say I don't remember how to use it well.

How do I test the battery with it? Set it to VOC 20?


11-19-2006, 01:04 AM
Yup. VDC, 20, should do nicely.

11-19-2006, 10:12 PM
12.5 volts on the button with the engine off.

To cold this evening when I had the chance to test to open the garage door and start 'er up, though. /ubbthreads/images/graemlins/smile.gif

But I am wondering if the alt is ok, and that it was just taking extra time to get the volt meter back to 14v after the loose wire was reconnected. But the ignition light is still on. <shrug>

Maybe I will take her out for a short spin tomorrow night after work to see if she recharges... if the weather gets better.

11-20-2006, 08:12 AM
When you start the car next time put the meter leads across the battery terminals again. You should see a 1 to 1.5 volt increase over that battery-only measurement of 12.5v. If you don't see that increase it confirms what the charge light is saying, that the alternator isn't charging.

The Smiths dash mount volt meters are bi-metallic just like the electric temperature and fuel gauges. Therefore they are very slow to respond to changes. On fuel and temp that's probably OK because the changes do happen a bit slower. The Smiths gauges still can tell you that something has happened, it just might take a bit more detective work to figure out what and when.

11-20-2006, 08:29 AM
I hope it's just the slowness of the gauge! I'll try and get her running tonight to test the leads and see where the gauge goes...

11-25-2006, 03:33 PM
It's not the gauge... /ubbthreads/images/graemlins/frown.gif I just took her out for a drive... the gauge keeps at about ~12 to 12.5 volts. Once I got her in the garage, I kept her running and popped the hood and checked. When running, the battery is at 12.1 volts. Shut her off... 12.5.

Should I replace the alternator?

11-25-2006, 04:42 PM
Well, you have two choices...
1. Replace the alternator
2. Have your alternator rebuilt

Every symptom you've described, the alternator light on, and the voltage dropping is indicative of the alternator not working as intended. /ubbthreads/images/graemlins/cryin.gif

11-25-2006, 06:21 PM
Eh... think I will buy one of the ones they have at TRF, and give it a spin.

Thanks gents!

11-25-2006, 09:03 PM
Well... take the alternator into the parts store first and have it bench tested before you spend any money. If they confirm that it's bad, read up on alternator swaps. Several have been mentioned here. If originality is important to you then by all means go with a Lucas unit. If it's not important to you, several of the alternative may prove more reliable.

11-26-2006, 12:10 AM
Non-Lucas alternator? <blink blink>

<starts to research>

11-27-2006, 08:31 AM
Oh... Delco, Mitsubishi, Nippondenso, Bosch, Motorola. Search long enough and you'll find advocates for each conversion. Delco is the most commonly discussed.

11-27-2006, 10:07 AM
Yes the GM/Delco was what I am leaning toward at this point for the extra juice, small size, and it being fairly easy to install. Not to mention half the price of a rebuilt Lucas alternator!

11-27-2006, 10:32 AM
BTW, guys... any suggestions for which alt for a 76? I have the air pump on my car, so it appears I cant use the ones people have been talking about using on their 6s.