87 B25 alternator grounding issues

[Andy348]

I have reason to suspect that my alternator grounding is all messed up. I have searched quite a bit and found that some alternators would ground to their mounting point on the engine block, which mine does not seem to do so. There are also some who say that it is grounded on the oil pan, along with the main block ground.

I bought Greg's upgraded grounding cables to attempt to fix the issue, but once again I'm not sure where to connect what. I asked Greg and he mentioned that it is to be connected to the starter. If someone could explain it to me in direct terms I'd be grateful.

This was the wiring on the back of the alternator before I took the engine apart:



Thanks for any help.

[jlevie]

It is easy enough to check for a grounding problem. Measure the resistance from alternator body to block. The measure the resistance from the block to a ground point on body of the car. The first test will tell if the alternator to block connection is good and the second will tell if the ground strap is good. Use A DMM so you can get accurate measurements.

[ForcedFirebird]

You only need the supplemental ground strap on the alternators that have rubber bushings. The solid mounted alternators will ground through the brackets.

[Gregs///M]

I have reason to suspect that my alternator grounding is all messed up. I have searched quite a bit and found that some alternators would ground to their mounting point on the engine block, which mine does not seem to do so. There are also some who say that it is grounded on the oil pan, along with the main block ground.

I bought Greg's upgraded grounding cables to attempt to fix the issue, but once again I'm not sure where to connect what. I asked Greg and he mentioned that it is to be connected to the starter. If someone could explain it to me in direct terms I'd be grateful.

This was the wiring on the back of the alternator before I took the engine apart:



Thanks for any help.

Your alternator is mounted without metal-to-metal isolation. Meaning, since it is mounted via metal to metal contact, that is your ground bonding.

The cable kit that you bought runs as follows.

Long alternator cable runs from the alternator output to the starter input. it connects to the same bolt as the other battery cables that runs to the battery junction block.

The ground cable runs from the oil pan bolt to the frame rail on the drivers side.

The cables are not supplementary cables but OEM replacements. So you will be replacing OEM cables for ground and alternator positive voltage output.

Hope that helps.

Why do you ask if your alternator grounding is messed up? Are you getting dead batteries? or poor output?

[Andy348]

Thank you to all for making things a little more simple for me.

My original problem was the alternator not charging. I checked voltage, found that I needed a new alternator, and rebuilt the alternator, bought a new battery, and changed the lights in the cluster. I have yet to turn the car on to see if this has all worked.

I have just hooked up both the alternator and the starter, implementing Greg's wire. Here are pictures of the two connections - let me know if they look correct.

Also, on the alternator there is a third post seen in the picture, a very small one next to the ground. It seems like this could have a wire put on it. Is there supposed to be one there?

And finally, each post for the alternator goes stud -> nut -> wire -> washer -> nut. Is there supposed to be a nut closest to the alternator, or is the wire supposed to be 'touching' the alternator?




photo sharing

[jlevie]

I think you mean that there is a third post on the starter, which would be the unloader switch. This being an 87, the presence of the unloader switch means that the starter has ben replaced with one from a later production car (production from 9/87 or later). You car doesn't use the unloader switch.

[Andy348]

Got it all hooked up and it finally charges. Now to hunt down idle issues.

Thanks to all.

[dnguyen1963]

Got it all hooked up and it finally charges. Now to hunt down idle issues.

Thanks to all.

Smoke test, baby.