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Charging woes

I'm using the volt gauge and a nice multimeter, they both give the same readings.

I've got a solid 13v with the AC and lights on, more like 13.6v with no load, which is good enough for now. I may try replacing the regulator.

get one of them fancy adjustable voltage regulators, more expensive up front but modern good quality batteries can charge to a higher voltage than the stock regulator can provide

Those Densos always go bad for some reason. I stick with the Bosch 100 amp alternators now and haven't looked back.

I want a 100a alternator but I don't want to mess with the stock 80a at this point. It hasn't let me down for a decade, besides a brush replacement
 
Maybe they good bad for you...

but not for the 200 other T-brickers that have got Denso alts from me over the last 14 years I've been hanging around here

The alt he got from me was tested and worked perfect in my 240.

There was something wrong with crazy's charging system before he got the Denso

and now there is still something wrong



Those Densos always go bad for some reason. I stick with the Bosch 100 amp alternators now and haven't looked back.
 
Maybe they good bad for you...

but not for the 200 other T-brickers that have got Denso alts from me over the last 14 years I've been hanging around here

The alt he got from me was tested and worked perfect in my 240.

There was something wrong with crazy's charging system before he got the Denso

and now there is still something wrong

I'm sure you're right, I just can't figure out what's wrong. At least now it's pumping out enough juice to power everything, but I'd still like to see 14v.

I've tested all the wiring and the battery light circuit. All seems to be good. I thought it must be the pulley slipping since jacking up the belt tension made an improvement, but the paint marks haven't moved.
 
There are a few places where you could get a large voltage drop in the charging system. It may be time to do some of the voltage drop checks that z always suggests. To charge the battery the B+ wire on the alternator goes to the starter. Then uses the positive battery cable to connect to the battery to charge it. Anywhere along that path could affect what ends up at the battery. Also the ground on the alternator goes to the block. Where it connects to the block is a spot to check. Then the block ground aka negative battery cable provides the negative side of the circuit to charge the battery and run everything. So the block ground from the negative battery cable is another spot where you can have a sneaky voltage drop.
 
The voltage drop test is legit! I mostly use it for slow crank diag on modern v8 trucks that intermittent slow or no crank.

By using jumper wires and running a redundant ground/power like suggested is also a great way to rule out the cables. It's worth busting out the meter and doing a few voltage drop tests, especially in the ground side. I wouldn't want to see much more than. 100 or 200 mv drop on the cables. Read up on how to do it. I'm not gonna tap it all out.

All that being said, if your battery is up in the 13's, it's charging. I wouldn't chase your tail too much on this one. You may find poor crimps using a volltage drop test and find much more current by replacing tired old corroded cables. Especially that alt ground cable that fails all the time. Especially on a greasy 240 down low covered in oil.
 

My other car makes 14.5v at idle with a 55a Bosch alt and an even bigger battery than in the wagon.

I cleaned all the main connections (Starter motor and battery ground) and replaced the alternator ground. One of the first things I did was a voltage drop test.

But yeah, I'm not really sweating about it anymore. Makes enough juice to run everything and charge the battery.
 
over-tightening the belt won't make any difference
Except for premature alternator bearing failure. I use some sort of belt dressing on a cleaned belt. An old candle has so many uses, including this and as a dry lube of house door strikers!

the block ground from the alternator
Beefing up that wire gained my 760T .5v under light and heavier load.

Also, the dash gauge reads low compared to a DVOM under the hood.
 
500 millivolt drop is a lot. When I check battery cables, I do a clear flood crank and if they read more than 250 millivolts the cables get replaced. They usually look great too.

I would replace that ground wire and repeat.
 
Well I think the Desno just died. Good belt tension, very little resistance to pos/neg terminals, battery light works normally. Light turns on with ignition and goes out with startup even though the Denso produces no power at all.

What options are out there for a Denso sized or smaller alternator?
 
Never seen a Volvo alternator put out 14.5V. 13.5-13.8 with no load. And my Denso 100 amp alternator works very well- pulled from a junkyard years ago- a nice upgrade.
You should have a ground from engine to body that is the same gauge as the battery cable.
 
Bosch 100 amp alternator from 1992 940 Turbo on my 1988 760 charges at 14.2 volts. No issues with cold winter starts. Using group 40R battery meant for a Ford. Group 40R is an International spec battery with 11 inch long case without end mounting lugs or carry handle.
 
Denso 100a unit in my 240 did have a broken regulator. It happens. Car ran fine with it just low-ish voltage and idle was unstable.
Idle is 14.2v now and sometimes drops from low alternator rpm (under drive pulley). Ground and positive cables new, I think I used 16mm? or 25mm?, that's awg 6 or 4. Good enough for the 100 amps the alt puts out, though slightly thicker would not have hurt. Voltage drop positive or negative connection to battery is minimal.
 
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