• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Generator not keeping up?

Share this page

M

Member 10617

Guest
Guest
Offline
Took another ride up on the Blue Ridge Parkway today. Ran into a lot of fog and turned my lights on. (Its' very rare that I ever use my headlights).

I noticed that with my headlights on, my ammeter needle moved halfway to the -30 position and remained there all the time that the lights were on. When the lights were turned off, the needle went back to "0".

Does this mean that my generator cannot keep up? And what else may it say about my generator?
 
What engine rpm? What do you have for headlights?

Yes, the generator was not keeping up and the battery was running down. But that is perfectly normal with the stock generator at idling or low rpm. It takes nearly the full output of the generator to keep up with the headlights, and it doesn't reach full output until 2500 (engine) rpm or so. (Approx 4500 at the generator shaft.)
 
I have HID (xenon) lights on the car. They were on while I was driving about 40-45 mph, at an average of about 2500 rpm, reaching at times 3000 rpm.
 
True HID (high intensity discharge) or fake?

A real HID bulb only draws 35-40 watts, but there will be a fair size electronic "ballast" for each bulb that turns the 12v into what the arc inside the bulb requires. But there are lots and lots of fakes on the market, that are really just quartz-halogen incandescents. Typically they do generate the high color index (blue-white) light that is commonly associated with true HID, but they also typically draw 2 or 3 times as much power. If you are running 90 watt bulbs, for example, the stock generator hasn't a prayer of keeping up.

One easy way to resolve the issue might be to take the car to some place that will test the generator on the car, including a load test. I'm not sure what they have in VA, but around here, O'Reillys will do the test for free and it only takes a few minutes.

Here is a site that sells the fake HID bulbs:
https://www.everbuying.com/product45669.html

And here is a shot of a typical ballast (which is required for true HID bulbs)
Extreme-HID-Ballast.jpg
 
Randall,

My HID lights are the real thing, including balast. The folks at the shop that put them in told me that they would draw less power than ordinary headlights. Which leads me to think that there is a problem with the generator ... the alternator... or both.

To be more precise, the ammeter remains at -15 when I run with my headlights on, even at 2500-3000 rpm. The needle returns to "0" only when I turn the headlights off.

I plan to take the car to the shop as soon as possible after Hurricane Sandy finishes its dirty work.
 
Yup, then you've definitely got a problem. Most likely the control box, IMO, but could be the generator itself.

A TR3A doesn't have an alternator (unless someone has added it), so I'm practically certain it's not the issue :jester:
 
Randall,

Sorry... I meant to write "Regulator" and not "Alternator." The regulator is almost brand new, but that doesn't mean that it's not bad. We'll see.
 
Say now! Here's something:

I checked in the Maintenance & Instruction Manual for Lucas Electrical Equipment, section 2, and found the following:

"A discharge reading may be given immediately after switching on the headlamps. This usually happens after a long run, when the voltage of the battery is high. After a short time, the battery voltage will fall, and the regulator will respond, causing the dynamo output to balance the load."

Yesterday, when I noticed this problem, I had been driving for about 1 1/2 hours before turning on the headlights. After a few minutes, I noticed the ammeter needle at -15 and holding, so I turned the lights off. Perhaps I didn't allow enough time for the battery voltage to fall, causing the dynamo output to balance the load.

Weather permitting, I will check this out this afternoon before the storm hits.

What do you think?
 
What I cited above may have been part of the problem, but I have fixed the problem in a much simpler manner... an embarrassingly simple manner: I cleaned the contacts on the generator and everything starting working normally again.
 
You are right! As I drove down the highway a few minutes ago satisfied that this simple solution was actually THE solution, I decided that I had to change the tag line. The same goes for my fixing my stator tube problem simply by tightening the stator nut.
 
Back
Top