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Hey guys, I'm new here. I registered a while ago, but this is only my second post. I bought my first Corvette, a 1975 4-speed L48, about three months ago. I've had a bit of electrical trouble since then. I've worked it on my own and now I need a bit of guidance from you folks.

So to get straight to the point, what is a normal battery gauge/ammeter reading for a 1975 Corvette? Currently, when I start it up, my ammeter will jump to about 20, and then lower down to about 3-5 amps idle.

Long story:

When I bought the vette, it was missing the alternator plug connector. Instead the wires were held on by electrical tape. The car started fine, the battery held a charge, etc... just fine so I didn't see it as much of a problem. None the less, two weeks later when I had the time I took it to the closest Corvette shop to get it fixed before it started to cause problems. They fixed it up no problem.

About a week later, that's when my battery started dieing on me. I noticed my dash lights and headlights were getting dimmer, and my ammeter was hardly registering even 1 amp when I had everything off (Lights, radio, etc...) I took it in to regular shop and they told me I had a bad alternator. I ordered a replacement alternator from Eckler's ( http://www.ecklers.com/corvette-alternator-70-amp-1969-1982.html ), and installed it. The only problem was the ground screw was too small to properly screw entirely into the new alternator. But it solved the problem of keeping my battery charged. Lights were bright, and it registered at least 10 amps pretty much all the time, and more like 3-5 when I had the lights, radio, etc.. turned on. When I revved the engine the ammeter went up, like normal.

I checked around at local shops to find a replacement ground bolt, but I couldn't find a match. At first I wasn't worried, because everything was working, and I was more focused on my next repair, the valve cover gaskets. Well the next weekend when I fixed the valve cover gaskets, I took it around the block to make sure I didn't screw anything up. All the gauges looked good, except now my ammeter was doing the same bad stuff as before. It was only showing a few amps, and not registering when I revved the engine. Before even a week went by, it was having trouble starting again, and before I knew it, the new battery was dead.

I jumped it and took it down to Pep Boys, where I bought my new battery. They tested it and told me it was bad and since it was still under warranty, I was entitled to an exchange. I upgraded to a Bosch and got a charging test done, and they told me my alternator was bad. I figured something else had to be going on, because no way a battery and an alternator both go bad in one month just due to factory defects.

So last monday I took it in to a different Corvette shop than the one that "fixed" my alternator plug connector the month before, hoping they could give me the correcting grounding bolt and that would solve all of this. The guy there was very helpful and told me that Eckler's sent me the completely wrong alternator (Boy was my face red), and the size bolt that fit the alternator was too big to fit through the grommet.

He hooked me up with a better fitting nut for the negative terminal, which solved one problem. After this, my ammeter would USUALLY read about 20 amps starting up, and then go down to about 3-5, and would usually hold 3-5 amps even when I had the headlights on. Point being, it was no longer going below 0 when I had the headlights on. But it still would not register when I would rev the engine, and I still had trouble starting it. Funny thing is, usually when it wouldn't start, I would just disconnect the negative cable on the battery, reconnect it, and it would start up (with a little hesitation but it would start. This makes me think I might have a bad starter and/or starter solenoid).

Fed up, I headed to NAPA to purchase another alternator.

So I installed the new alternator today. All the connections fit properly, Vette started right up. Lights are bright and I did a battery check and the battery is still good. BUT... the gauge still only reads about 5 amps at idle. It will jump up to 20 when it starts, but it goes down to 5. It holds in the 3-5 amp range with the headlights and radio on. But it STILL does not register when I rev the engine. I don't know what is going on. The only thing I can think of is that maybe I need new battery cables. The negative battery cable connector has some corrosion. I cleaned it off when I bought the new battery and even took the advice from Pep Boys to get some of those felt terminal protectors. Any ideas?

This is probably unrelated, but just in case: my tachometer is out too. I plan to purchase a new filter and circuit board and fix that here in the next few weeks. Plus, I'm pretty sure its not related because the tachometer was out before I had any of these problems, and it was out when I first installed the Eckler's alternator and the gauge was registering when I would rev the engine.

On a somewhat unrelated note, I am looking to do a tune up here either the same day or right after I fix the tach. Any recommendations on parts? Should I stick with the R44TX or are those garbage? Are all spark plug cables the same or should I spring for something a bit more pricey? Thanks for any advice!
 

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Check that plug that plugs into the side of the alt. make sure the fix the corvette shop did is correct.
You need to make sure the terminals in that plug are getting good contact and the wires are not reversed.
clean the neg. bat, ground at the frame its write under the bat. compartment.
 

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Your ammeter may be dying -- it's forty years old.

Check the tach wire connection on the dritributor; they can get loose/dirty.

:thumbsup:
 

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Discussion Starter #4
Thanks for the help, I'll try out those suggestions.

Any advice on spark plugs and spark plug wires? I just want to make sure I don't buy junk for my tune-up. I am looking at the Bosch Platinum spark plugs. I've also heard that braided spark plug wires are good. Any thoughts?
 

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T...Any advice on spark plugs and spark plug wires? I just want to make sure I don't buy junk for my tune-up. I am looking at the Bosch Platinum spark plugs. I've also heard that braided spark plug wires are good. Any thoughts?
Bosch Platinum for a daily driver would be overkill. Stick with AC Delco or Champions and you'll be fine.

The braid on braided plug wire is only to inhibit radio interference. You probably do not need them on a smallblock. A good set of tailored C3 wires is all she needs.

:thumbsup:
 

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Hey guys, I'm new here. I registered a while ago, but this is only my second post. I bought my first Corvette, a 1975 4-speed L48, about three months ago. I've had a bit of electrical trouble since then. I've worked it on my own and now I need a bit of guidance from you folks.

So to get straight to the point, what is a normal battery gauge/ammeter reading for a 1975 Corvette? Currently, when I start it up, my ammeter will jump to about 20, and then lower down to about 3-5 amps idle.

Startup is a little high, possibly showing a discharged battery, but otherwise normal.

Long story:

When I bought the vette, it was missing the alternator plug connector. Instead the wires were held on by electrical tape. The car started fine, the battery held a charge, etc... just fine so I didn't see it as much of a problem. None the less, two weeks later when I had the time I took it to the closest Corvette shop to get it fixed before it started to cause problems. They fixed it up no problem.

About a week later, that's when my battery started dieing on me. I noticed my dash lights and headlights were getting dimmer, and my ammeter was hardly registering even 1 amp when I had everything off (Lights, radio, etc...) I took it in to regular shop and they told me I had a bad alternator. I ordered a replacement alternator from Eckler's ( http://www.ecklers.com/corvette-alternator-70-amp-1969-1982.html ), and installed it. The only problem was the ground screw was too small to properly screw entirely into the new alternator. But it solved the problem of keeping my battery charged. Lights were bright, and it registered at least 10 amps pretty much all the time, and more like 3-5 when I had the lights, radio, etc.. turned on. When I revved the engine the ammeter went up, like normal.

I checked around at local shops to find a replacement ground bolt, but I couldn't find a match. At first I wasn't worried, because everything was working, and I was more focused on my next repair, the valve cover gaskets. Well the next weekend when I fixed the valve cover gaskets, I took it around the block to make sure I didn't screw anything up. All the gauges looked good, except now my ammeter was doing the same bad stuff as before. It was only showing a few amps, and not registering when I revved the engine. Before even a week went by, it was having trouble starting again, and before I knew it, the new battery was dead.

I jumped it and took it down to Pep Boys, where I bought my new battery. They tested it and told me it was bad and since it was still under warranty, I was entitled to an exchange. I upgraded to a Bosch and got a charging test done, and they told me my alternator was bad. I figured something else had to be going on, because no way a battery and an alternator both go bad in one month just due to factory defects.

So last monday I took it in to a different Corvette shop than the one that "fixed" my alternator plug connector the month before, hoping they could give me the correcting grounding bolt and that would solve all of this. The guy there was very helpful and told me that Eckler's sent me the completely wrong alternator (Boy was my face red), and the size bolt that fit the alternator was too big to fit through the grommet.

He hooked me up with a better fitting nut for the negative terminal, which solved one problem. After this, my ammeter would USUALLY read about 20 amps starting up, and then go down to about 3-5, and would usually hold 3-5 amps even when I had the headlights on. Point being, it was no longer going below 0 when I had the headlights on. But it still would not register when I would rev the engine, and I still had trouble starting it. Funny thing is, usually when it wouldn't start, I would just disconnect the negative cable on the battery, reconnect it, and it would start up (with a little hesitation but it would start. This makes me think I might have a bad starter and/or starter solenoid).

Fed up, I headed to NAPA to purchase another alternator.

So I installed the new alternator today. All the connections fit properly, Vette started right up. Lights are bright and I did a battery check and the battery is still good. BUT... the gauge still only reads about 5 amps at idle. It will jump up to 20 when it starts, but it goes down to 5. It holds in the 3-5 amp range with the headlights and radio on. But it STILL does not register when I rev the engine. I don't know what is going on. The only thing I can think of is that maybe I need new battery cables. The negative battery cable connector has some corrosion. I cleaned it off when I bought the new battery and even took the advice from Pep Boys to get some of those felt terminal protectors. Any ideas?

Reving engine has little to do with it. The alt will charge more at rpm only if the battery needs it or if the part of the system the ammeter sense needs it. On a 75 the ammeter doesn't sense the alt pos to headlight juice unless it is drawn from the battery.
To properly test for charging, get a multimeter that can handle some amps and test at the pos term of the alt and at the battery. You can also test with a cheaper meter in volts, 14.7v max at the alt and 14.2v max at the battery.


This is probably unrelated, but just in case: my tachometer is out too. I plan to purchase a new filter and circuit board and fix that here in the next few weeks. Plus, I'm pretty sure its not related because the tachometer was out before I had any of these problems, and it was out when I first installed the Eckler's alternator and the gauge was registering when I would rev the engine.

Probably need a new tach board it connections are good.

On a somewhat unrelated note, I am looking to do a tune up here either the same day or right after I fix the tach. Any recommendations on parts? Should I stick with the R44TX or are those garbage? Are all spark plug cables the same or should I spring for something a bit more pricey? Thanks for any advice!
Get a little can of this
http://www.permatex.com/products/automotive/lubricants/specialty_lubricants/Permatex_Copper_Anti-Seize_Lubricant_b.htm
You will use it for electrical plus bolts.
Clean all your ground points on the car Neg battery cables, starter brace to engine mount arm, battery connections etc.
Mix up some baking soda and hot water and dip the battery cable ends to remove any oxidation, then coat with copper and reattach to battery. Will last a long time.
 
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