Hey all
I recently picked up a 1986 Volvo 245 manual with the B230F, 190k miles; it runs really well but has a charging issue.

The battery light on the dash comes on with the key and goes off when the engine is started, the alternator will start charging up to 13.5 - 14V at idle, then after a few min it'll stop charging and the voltage at the battery will drop to ~12.7V; car just at idle.
Sometimes the dash light will come back on, sometimes it wont -- but if I put the car in gear and try to drive it the dash light will usually come back on (indicating it's nolonger charging).

If I let the car sit for a bit and try again the cycle will repeat -- it'll happily charge for a minute or three, then drop back down to battery voltage.

The alternator that came on the car is an AC Delco rebuild, I bought another rebuilt alternator and it does the exact same thing.
I know the quality of the rebuilts can be questionable, but it seems weird that two different alternators fail in the same unusual (?) way.

I've replaced the alternator ground, and ran a temp wire from the alternator's ground directly to the battery.
Voltmeter says there's a 0.04V voltage drop between the alternator's positive wire and the battery, which seems fine (?). I may go ahead and swap out the alternator's positive wire as well.
Battery is an Interstate, it happily cranks the car over and seems to hold a charge well.
Also replaced all three alternator bushings, and used a small pry bar to put a little extra tension on the belts.

Rigged up a test light to take the place of the dash light excite circuit; it's on when the engine is off and off when the engine is on, just like it's supposed to be; so more than likely not a problem with the excite circuit.


..Then took the Volvo's wiring out of the loop entirely with a pair of jumper cables hooked from the battery to the alternator's pos and neg terminals, with the above excite wire bypass clipped on; all the Volvo's wires disconnected from the alternator.


(...cleaning the engine bay is on my to-do list, wanted to get it running well first)

Did the exact same thing, charged initially then stopped and dropped back to ~12.7V with the engine at idle. Revving the engine made no difference.
So.. it seems reasonably likely that both the alternator that came with the car and the new alternator are bad?

Bought the replacement alternator online so I've got a request in to swap it out / refund, maybe third time's the charm.
Anything else I should be checking?
It seems like a relatively simple circuit, frustrating that it works initially then stops.

And any opinions on the various rebuilt alternators (NAPA, AdvanceAuto, AutoZone, etc) or are they all about the same?
I'd like one of the Bosch rebuilts but they're out of stock eveywhere I've looked.

 

Can you replace the voltage regulator on its own? Did you check cables/wiring/ground? The problem sounds like there's a relay that's overheating and sticking - could be in the regulator or elsewhere in the circuit that prevents over charging. I don't have a wiring diagram to consult but that's where I'd start.

 

It's dropping down to CLOSE to battery voltage. Have you measured the charging amperage with a non contact ammeter?

What is the voltage at idle (and at 2000 rpms) with the headlamps, wiper and heater fan on?

Years ago when those cars were common and customers batteries went bad due to old age - it was common for bad alternators to be diagnosed by SEARS (and others used to other manufacturers charging rates) when they were replacing the old bad Die hard. My customers would come in and I would have to reassure them that a Volvo charging at 12.8 volts with a fully charged battery is perfectly normal. They would drive away usually still not sure of the situation (because of the dire warning from Sears) but would accept my explanation - after their car continued to run without the battery going dead or having to replace the alternator.

 

Interesting. Good to know, thanks!
I'm used to vehicle charging systems that always keep the voltage at the battery above 13.5V or so -- I guess Sears was too.

The only reason I started down this path was that the battery warning light would come on with the engine running.
Pretty sure the old alternator was having issues, but plausible I misdiagnosed the new one...

I swapped the old alt back in yesterday to verify it was dead, then pulled it and ordered new belts + another rebuilt alternator from NAPA this morning; hopefully pick it up this afternoon and give it a shot.
Was wondering if the old belts were allowing it to slip, they look fine but no idea how old they are -- I get the impression this car hasn't been driven regularly in a long while, cleaned what felt like a decade of tree staining off the roof.

As long as the dash light stays off while driving, regardless of voltage at battery, it should be alright then?
I currently lack a non-contact ammeter... will take an excuse for a new tool though

Thanks guys!

 

Another question -
The NAPA rebuilt alt came with a more open fan setup



It'll likely move more air, but I'm guessing the original, more protective style is due to the alternator's placement basically under the car.
Would you swap fans or run it as is?

The flower-style fan on the rebuilt has a Bosch logo + Germany stamped on it so at least it's decent quality, just not sure if it's appropriate for this use case.

 

Ah. I do believe I found my main problem.
The harmonic balancer is now two pieces lol.

Went to go change out all the belts and was able to free spin the main pulley.
Wasn't making any noise, but at a guess it was slipping enough that the alternator wasn't getting spun fast enough to properly charge -- esp after the engine warmed up a bit.

 

I have replaced many of those when they slip - usually found them when attempting to set the ignition timing (obviously on older cars) or when they squealed - sounding like a slipping belt but the belts were tight.

For the alternator fan - either one will work fine (as long as the spacing is correct) but I might choose the smaller pulley - so the alternator spins faster. (if one is smaller)