I have been struggling with the alternator from my 1970 Convertible Corvett e, for several weeks now and I am still puzzled by the fact that it just do es not give any output.
It all began when I tried to get another alternator that had a lot of probl ems working on another engine, where I wanted to charge the battery so I bo rrowed the Alternator from the Corvette just to produce a quick charge. It did not work and when I looked inside there were a lot of problems, howeve r I had a lot of old alternators from that era, so I felt quite confident t hat I could fix it.
To start with it has the internal regulator and so is not the original but I am not worried about that so much as the fact that the ignition light sta yed on and there was no output.
I found that both the diode trio and the rectifier pack were corroded, it h as been unused for several years, so I was not all that surprised. I got the spares form another old alternator of the same age and type, but even t hough the diodes and the rectifier pack tested OK there was still no output . Changed the brushes checked the rotor and the stator windings and found t hem OK. I made sure that the insulated screws were in the right places and as there was still no output, I got my 1978 Chevrolet manual out, which is very good at diagnosis.
The only thing left was the regulator module which I don't know how to chec k. I had several of them and felt sure that one would work. I rigged it u p to be driven by an electric motor on my bench, so I could see what was ha ppening. With three different regulator modules I got the same fault. When I grounde d the "D" connection on the brush block, all that happened was the ignition light brightened a bit. The alternator was being driven at about 2500 rpm at this time. The battery was connected via an ammeter, terminal 1 on the regulator, was going to the ignition light then to the battery. Terminal
2 I linked to the battery positive and the negative battery went to the fra me of the 10SI.I noticed that there was a plastic ring on the battery charging terminal an d it was blue. This started me wondering as to the identity of the alterna tor. I seen to remember this was a red plastic collar on another alternato r. Is it possible that I have got a mixture of negative earth and positive earth alternators. Is this why it just does not charge? If it is a negati ve earth machine will the rectifier and diodes be reversed or how does it w ork? The fault finding guide in the manual say it is a fault with the dio des and/or rectifier. This makes sense but I have re-done it all so many t imes. I even went on You Tube to watch a video on how to do it all, but now here is reversed polarity even mentioned.. There were cars with positive e arth during this era, wasn't there?
Is the regulator module the same for all + and - alternators? I just can't see this being the case and maybe I have been damaging all sorts of bits by mixing them. I have used three different bodies and bits now but always w ith the same result, I must be doing something wrong. Anyone got the answe r, Please!
Regards George.