Alternator issue

[phaetn]

Still have a niggling issue with my Ford style 95amp alternator.

Earlier this year I pulled the alternator and had it bench tested at a specialty alternator shop. Best in the city. I saw them hook it up, and saw the tester indicate 14.5v. They did install a new pulley as mine had grooves so the belt would slip.

When I first put it back on I confirmed it was putting out over 14v at the battery under idle. Worked fine for a few weeks. Saw a friend who said I had the belt too tight so it might be hard on bearings (water pump, alternator) so I loosened it a wee bit. A few days later, the alternator charging light come on but there was no sound of a squealing belt. I tightened back the belt to where I had it before just in case that was the problem.

Light still came on, especially on start-up but can fade away after a while. I even had a harder than usual crank the other day and then signal lights seemed a bit dim or slow (flasher issue), indicating a low-charged battery. Put it on a trickle charger overnight.

Next morning, with fully charged battery (12.7v) dash light still on after starting but doesn't stay fully bright but dims after a while. When I got home after work, I tested with voltmeter at the battery. 12.5 volts at idle (uh-oh) and down to 12.3 with all lights on, including turn signal, and the rad fan. After turning the car off, battery voltage rose back up to 12.7, where it should be at rest. Clearly when running I'm draining the battery.

My understanding is the alternator is solid-state. If it worked at the bench test then it should still work -- it's binary - either works or doesn't, it's not like a diode could be good one day, bad the next, and then good again, right?

What should I look for? Bad ground? Water level in battery? It's relatively new (less than two years and has a four year warranty) and I had it quickly tested last year (not a deep cycle or anything) but a quick test at a counter.

I gather I should use a voltmeter at the alternator output post (there are a lot of ring terminals connected on there) and presumably a ground (engine block). What am I looking for? Anything else do to?

With thanks and cheers,
phaetn

[phaetn]

The mystery deepens.

Now the alternator charging light on the dash isn't lighting up at all, not even at startup. I wonder if it's a connection issue or something else.

I will trickle-charge it tonight and see if it lights up in the morning. Maybe voltage has dropped so low (now under 12v) that it's just not lighting.

Cheers,
phaetn

[baltobernie]

Can you tell us how you wired the Ford alternator into the Spider harness? Are you still using the Fiat relay to trigger the alternator warning light?

[phaetn]

Good question. The short answer is I dunno. It was in place from the previous owner.

I can take a pic and post.

Cheers,
phaetn

[spider2081]

can you post a photo of the alternator electrical connections and the part number??? The part number might be on the case somewhere.

[So Cal Mark]

on a 74 you have to make sure the oem voltage regulator and charge light relay are bypassed for the 95a alternator to work properly

[phaetn]

Thanks for all the replies, folks.

Turns out it was simple fix, but it took me a while to identify it. Suspecting a loose ground the other day, I had verified the ground strap plus wiggled the battery post cables. They were all tight.

Today, when improving wiring on the alt I first had to disconnect the battery. When putting the negative cable clamp back on after cleaning up some connections that I had never liked, I immediately found the problem. The clamp was split well more than in half from the bottom up!! It wasn't apparent from the top but clear as day when slipping it on. Less than $15 to buy a new 1 gauge battery post cable. Two minutes to install and then started the car. Immediately the charging dash light came on brighter than ever and, at idle, the alt tested over 14v from the alternator post and then also confirmed at the battery.

Problem solved!

Thanks again for the help. It took a while, but at least I cleaned up some wiring and connectors before I found the problem.

Cheers,
phaetn

[spider2081]

GREAT !!!!