Alternator question

[MissouriJim]

What is the voltage at the alternator
when the car is running?

12.4-ish volts, same as battery (well a little less) with car off. It's not putting out any charge. FWIW, also checked continuity on Big Red Fatty (main + cable) from alt. to battery, it's 0.00 ohms

[MissouriJim]

I have pulled the alternator, and removed the regulator.

Can anyone tell me which points on the reg. should have continuity? Again, the exciter pin doesn't seem to ever reach ground, as the dash light never comes on, but does come on when I directly ground the exciter wire.

TIA!

[WhatAmIDoing]

I have pulled the alternator, and removed the regulator.

Can anyone tell me which points on the reg. should have continuity? Again, the exciter pin doesn't seem to ever reach ground, as the dash light never comes on, but does come on when I directly ground the exciter wire.

TIA!

What shape are the brushes in? Look for blown traces / components on the board. These voltage regs are kind of hard to test. They either work or they don't.

I would just order a new voltage regulator, ~$40. Reduced the risk of having to do it again.

Can you advise where I can source this? The only inexpensive ones were Chinese-made on Ebay from relatively unknown sellers.

IPDUSA has them for around $200

Always check FCP Euro

[BEJinFbk]

The internal regulator doesn't respond like old school units.
Internal means just what it sounds like. Similar to a GM 3-wire,
all of the magic happens inside the alternator. It just monitors
system voltage and excites the field when needed.

IIRC, it sees system voltage through the little R/W wire on the
alternator and all that grounding it does is provide a ground to
the light in the dash like a dead alternator would and lights it up.

Since the regulator is looking for positive power on that lead,
I'm not sure if grounding it is a good idea.
The diagram displaying this connection is attached:
.

1998_S70_V70_C70_Coupe - ALT and Starter.pdf

(400.13 KiB) Downloaded 72 times

.
And being a self contained unit, I'm not sure what to advise
as far as testing it. If it isn't producing 13.8 vdc or better and
the brushes look good, replacement is probably your best move.

Many believe that OEM Bosch is the best option for this.

[MissouriJim]

@ BEJinFbk Thank you - again, I only grounded it to prove the Charge dash light actually works and wasn't burnt out. A little confused why Volvo would rely on the actual circuit rather than a secondary test circuit for such things, but alas, such pondering is of little use

@WhatAmIDoing The brushes look burnt, if that makes any sense. One is substantially shorter than the other. They look worn - as they should, after 400K miles.

Anyhow, thanks for all the help, I found the unit on FCP for much less ~ should arrive next week. I think I'll visit the yard anyway this weekend & grab an extra just in case, plus that power steering pump. If it's not needed, I can always re-sell.

FWIW, and it's probably mentioned elsewhere, but removing the upper radiator hose makes all the difference when yoinking the Alternator up and out. Yes it's a bit of an irritant to use the catch-pan and top off the coolant, but it's better than ruining hoses and wires.

I'll post back here with final results.

[Chuck W]

The brushes look burnt, if that makes any sense. One is substantially shorter than the other. They look worn - as they should, after 400K miles.

The rest of the alt is probably fine, just the brushes on the regulator are worn out. I've actually successfully replaced the brushes on a couple of alternators (The current one in use in the wife's car is running a "re-brushed" regulator.

[Cees Klumper]

I would install a new alternator, not much more than only a voltage regulator and it's a wear item. When ours failed, the charging light also did not come on. One day it was just 'over and out'. X2 on ensuring all cables are tight including ground strap to the engine and chassis.

[MissouriJim]

I picked up a salvage alternator over the weekend & all's good. Key on, I get my battery dash light, and started up it's passing 14.4v across the positive terminal now.

I also ordered the regulator and confirmed the old one is bad, as the new one (and the salvage alt.) read 10 mega ohms across the exciter pin - to - positive terminal but the bad one reads infinity (open circuit.) Not to say they'd all fail this way, but mine did.

So, I'm all set, plus a spare alternator to keep in the trunk because we all know they usually decide to go out on long road trips...

[scot850]

Thanks for closing this out for us! Glad you found the solution.

Neil.

[PeteB]

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