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Discussion Starter · #1 ·
Just drove my GT over 120 miles at one time- back and forth to the Houston Opel meet. Went for an additional long drive tonight with
the lights on. Put the battery charger on to see how my battery was
holding up and it peg on the discharge side. Now I checked my wiring
to the amp gauge. The bulb is good and the wiring is correct, it just
doen't light up when starting. I am showing a slight discharge or no
discharge when running during the day with the radio on. When I run
all of the lights- parking, headlights and fog lights- my horn just
croaks- not enough juice I'm guessing. My battery usually lasts
about a month or two with out having to be recharged. I am starting
to wonder if either my alternator (used) or my voltage regulator
(even more used) are any good. Is there any type of test or
procedure to find out?
Texas Tom
good
 

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Had the same problem

In use to have the exact same problem. I replaced my OEM (high dollar crap) with a 65 amp GM internally regulated alternator. I did have to do a little modification to the bottom bracket (can be done with a side grinder if you have a some what steady had and a pretty good eye eye, it's how I did mine) the upper bracket I replaced with a modified one (I think I got it off a 68 Jeep CJ-5 with a nail head V-6), the modification to it requiered a drill bit and a drill. The wireing was pretty simple too. If you are interested in going this route which works very well for a daily driver or if you want to drive it more than two days a week at night (the third day I had to jump mine off after driveing home from work at night) but if you want to stay original it's obviously nothing you want to do to your all ready hard to find parts. If you are interested in going the same route I did and need measurements, pictures ect... please feel free rto msg or e-mail me. I'll be glad to help any way I can.

PS the hardest thing about changeing over to the much cheaper, much easier to find GM model is getting it by the starter (takes alot of patiants) or the easy way (I just found out today) take radiator out, it'll slide rite out the front.
 

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70's Opeler, back 4 more!
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There's already a thread here on the 65amp GM alternator swap. Just do a search on Alternator and headlights. It has a pretty good break down of other alternator possibilities and experiences.

You can take your alternator into a shop or parts store and have them test it to check the health. NAPA does this as does Advanced Auto and others. Then you can make a discission on what to do. At least you won't be wondering what is going on.

I went the way of the GM alternator and it is very simple, plus you can run so many more accessories. Also, for brighter lights, look into wiring in a relay to drive your lights directly from the battery.
 

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info on other site

Tom, There were a couple of tests brought-up on the ClassicOples site for you. It's too early in the AM for re-typing.

Chapter 68-9 in the factory service manual should get your problem solved. If you don't have the factory service manual, perhaps someone can send you the page(s), as my soon-to-be ex-wife now has my scanner.
 

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Discussion Starter · #5 ·
Just put the dash back in after doing some wiring mods during the Holiday break. Got the voltage reg replaced.double checked the wiring from the alternator per page 120-81 of the 71 Opel service manual. Now the alternator light comes on along with the oil pressure light, but after starting the engine, the oil light goes out and the alt stays on. Guess that say that the alt is bad. any one out there want to confirm this.
 

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Guess that says that the alt is bad. any one out there want to confirm this.

Or, the regulator is bad. Or one of the connections from the regulator to the alternator is bad. Or the fan belt is loose. Or...? I am always suspicious about blaming something that worked until some other changes are made.

There is a procedure listed in the FSM where the regulator plug is "jumpered" to send full field current directly to the alternator. Just remove the plug from the regulator, and insert a jumper wire between the two opposed terminals on the plug. This should cause the alternator to "put out" full current, which you should see on the dash ammeter. And a voltmeter should confirm this.

If it doesn't, then the alternator is probably bad. To double check, most auto-supply stores offer a free alternator check service, where they mount the loose alternator on a test bench with a driving belt, and run it through a diagnostic test.

Is your new regulator an electronic model, or the old "points" type?
 

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Discussion Starter · #7 ·
<Is your new regulator an electronic model, or the old "points" type?>

I put in a new one from Auto Zone so it must be an electronic one. All the wiring is new. Continuity on all wiring checks OK. New belt and no slippage. Harness fron Alt to Reg is new. Ground fron Alt to frame good. Every thing checks OK. Measuring across the fuse block while idling only measure 12 volts. Got to be the alt!
 
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