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Opeler
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Discussion Starter · #1 ·
After a nice drive around Washington D.C. last night I pulled back in the garage and noticed my headlights dim (slightly) as the RPMs dropped. Before I rush out and replace the alternator, I figured I'd check with the more experienced "Opelites" of the world. Any chance this is really a simpler matter? All I had running in terms of electricity was the headlights, a small 75 watt amp and a CD player powered by the cigarette lighter (so basically not much of a drain at all).
My drive was intended to ensure all was well with the GT before the trip up to Carlisle... Not sure I want to tempt fate with a bad alternator though!
 

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Old Opeler
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5,564 Posts
After a run the volts should be up and everything charged.
How old is your battery? You can get the output of the alternator checked for free at most battery places or spares outlets.
 

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1000 Post Club
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4,117 Posts
How Old is your Alt. and regulator? Is the regulator mechanical or electrical?
Does your Amp gauge go (-) and return to (+) when you step on the gas?

I've had better luck with the solid state regulators. The mechanical ones seem to go (-) at higher RPMs than the solid state ones.

My GT goes slightly (-) when I'm at idle with the H-4 headlights on but returns to (+) as soon as I accelerate. All of the Opels I've had has done this. Just my $0.02
 

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70's Opeler, back 4 more!
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398 Posts
I'm running the GM alternator and I see the same thing. At idle the charging voltage drops. Now, I have my headlights wired with relays directly from my battery, so they don't dim like they use to.

Does your charging jump back up as the RPMs increase?
 

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Opeler
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62 Posts
Discussion Starter · #5 ·
When I get home from work I'll have to spend a few minutes playing with the throttle and watching the gauge, because honestly, I was in a rush last night when I noticed the problem and didn't get to spend any time with it. I've had pretty good luck learning as I go with this car, but electricity has always been a bit "magical" to me, no matter how many physics classes I take! I can't say I remember my gauge ever dropping into the negatives. I'll take notes and get back to you all this evening! Thanks for offering your thoughts!

Unrelated question: Just out of curiosity, what mark on the temp gauge do most of your cars reach when running at full temp? I'm not having a cooling problem, I'm just wondering...
 

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OPEL-LESS!!!
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i run right about in the center of the guage, faces nearly right at the ground, perfectly vertical. not sure what mark it is...........
 

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Member
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1,219 Posts
Battery vs. Alternator voltage

In a properly wired car, (adequate wire size), the output voltage from the alternator, the battery voltage and the headlight voltage are all the same. If they are significantly different, there is a bad connection somewhere. The stock voltage regulator on all Opels is adjustable. A bad regulator can be ruled out by shorting across the alternator to regulator wires. This tells the alternator to put out maximum voltage. The most common cause of dim headlights would be a fan belt slipping.
 

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Opeler
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62 Posts
Discussion Starter · #9 ·
Well, I took the car out for a pretty long drive yesterday (sitting in the garage watching the gauge just didn't seem appropriate on a nice day). Here's the story- The gauge never goes above the first positive mark, but it never gets in the negatives either. It does move around a bit when I'm using the blinker or the brakes. I can't ever remember the gauge reading very high in the years I've owned the car. I figure I'll head to Carlisle anyway... I'd rather have a car that is broken because it's used than a car that works because it isn't! :)
I'll check the belt... But it was fine when I checked a few days ago. The wires are getting pretty old... I might need to get into that project soon. I appreciate all your help so far!
 

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Old Opeler
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Drive It!!

Sounds like your alternator is doing its standard best! It has kept things going for 30 plus years - so drive it!
Remember - if the alternator stops charging you can still drive as long as the Headlights are not needed. Just pick up another $39.95 battery from a service station so that if the battery does completely discharge and the car won't run you can just swap the new one in and get home.
 
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