Major issues with my 1972. Is an alternator from a 1975 internally regulated?

[1972_Buford]

Just bought my 1972 truck for $800 and battery is dead. Battery is brand new. I took the alternator in and it tested bad. I learned from the connectors on the alternator it is not from a 1972 but from a 1975. Were the 1975 alternators internally regulated? Reason I am asking is because the external regulator is still hooked up.

The problem I am having now is, I installed the new alternator (1975) and tested the alternator with the volt meter at the battery. Ended up with 11.8v while running......

I am guessing the alternator is not hooked up properly but would having both internal and external not allow the battery to charge?

Thanks
B

[1972_Buford]

Here is the alternator and the regulator I have.

[JimKshortstep4x4]

Judging from your pictures you have an internal regulator alternator hooked up to an external regulator so it will not charge properly. Try doing a search on converting to internal regulated alternators.

Jim

[1972_Buford]

thanks. I have done quite a bit of research on it already and got a pretty good hold on what needs to be done now.

I also have a question on the vacuum line for the distributor. Where does it plug into the carb at or does it matter which port. My last 350 was a 68 camaro and that was over a decade ago. I thought it should be plugged into one of the lower ports. Any suggests would be great. Thanks again.

And if anyone else has any input on the alternator the more the better.
B

[GASoline71]

What carb is on the truck now?

Gary

[ole dollor]

if you tested the alt. and it tested bad, then just get another alt. and see if it charges the way it was hooked up, if it dont, then you will need to change up the internal regulator wiring , you can use a wire from your old reg. to excite the new alt. hot when ign. on and dead when ign. off.

im sorry did not know the second pic was yours. it's got a new alt.... trace the wires and see if they are hooked up the the old reg. on the internal reg. alt. the battery terminal wire will be hot all the time, on your alt. run your white wire back to the battery terminal on the back of the alt the battery hot all the time terminal...the other brown wire will need to to be hooked up so its hot with ign. on and dead with ign. off then you alt. should start charging...right now all you are reading is battery voltage....hope this helps.

[1972_Buford]

That is basically what I did but it was not charging. I changed it to a internal configuration. I had to jump the battery though as it was getting lower and lower volts. After I changed it it read 12.6volts when running. From what I know it should be around 13.5v but I am guessing it may be because the battery is not fully charged. I let it run for about 15-20 min and shut it off and turned it on. It fired right back up but I am not totally convinced it is completely solved until it shows 13.5ish volts coming out. I have to wait until tomorrow as I cracked a rubber fuel line when changing the alternator. The line is got a small spritz coming out of it and I figured I did not want to have any electrical sparks with the leak. But, I feel it was a small victory none the less as it does show a small charge.

Eventually I am going to order a painless wiriing kit and go through it but little at a time. For now it is just my little work truck for house projects.

[1972_Buford]

OOPS carb is a Rochester 4 brrl. I just rebuilt it and found the little clip that holds the float to the needle was missing.

[bundeber]

This needs to be hooked up to one of the lower ports on the carb. The higher up on the carb the less vacuum as the rpms increase. Just test a port by putting your finger over the tube and give the engine some rpms. If it still has vacuum you're good.

[1972_Buford]

Thanks for the help. I fixed the fuel leak and checked the battery again this morning. While running, it was up to 13.2. I always thought when the alternator was charging it should show 13.5+ but like I said in the previous posts, the battery wasn't fully charged so I don't know if that is effecting it. Thanks again for all the help. I will put some pics up soon. It is nothing special to look at though.

Next I want to get rid of the gas tank behind the seat and replace it with a tank in the rear. I have the dual side tank options and the PO left the two tanks in the bed of the truck for me. He told me they were for the dual side tanks but I prefer just to have the one rear. I'll just see if someone on craigslist wants these.

[bundeber]

you'll find with the internally regulated ones that it takes more rpms than idle speed to charge fully. at about 2000 rpm it will charge over the 13.5 mark.

[VetteVet]

Unplug your external voltage regulator and jump between the brown and white wires and the red an blue wires and trace the wires to the alternator and make sure that the brown wire/white wire is going to the no. 1 terminal on the alternator and the red/ blue wire is going to the no2 terminal on the alternator plug. The large red wire on the alternator is left as is.

Here is the diagram for the conversion.



It should charge just fin and you can do away with the external voltage regulator or just leave it. If you have the ground wire to the alternator you can remove it because the 12 SI alternator will ground through the case to the engine block.

[1972_Buford]

VetteVet-
I may have done this wrong then. I followed this link which you recommended in another post:
http://67-72chevytrucks.com/vboard/s...d.php?t=119379
is this incorrect? Do I need to change it to what your above diagram says?

Basically I just hooked the blue and brown wire together at the alternator and put them on the no.1 plug at the alternator. Then the no. 2 I jumped to the post on the back of the alternator. Is this wrong?

[1972_Buford]

Nevermind, actually now that I have looked at it, it looks like it is basically the same except I just jumped the 12v source from the alternator rather than at the old regulator. Thanks again for all the help.