My 1992 740 is having a battery charging issue which seems to be connected to the dash lights.

The battery is not charging and the voltage reading across the battery terminals with the enginge running is only 13 volts.

The alternator and battery are less than 1 year old but I removed the alternator and had it bench tested, it checked out good.

Now the interesting part here is the dash lights, they are out, I believe everything but the SRS and "upshift arrow" are out no matter what position the key is in.

So the alternator is not being excited by the battery charge lamp. But why would all of these lights go out at once? Sounds like a fuse to me, possibly wiring. I haven't had a chance to look further into it, just thought I would get a jumpstart on the potential causes.

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'89 240 wagon, '90 740 sedan, '92 740 wagon

http://www.brickboard.com/RWD/volvo/1555715/940/960/980/V90/S90/completely_rebuilt_alternator_still_wont_charge_vehicle.html

check out this link. It turns out I just had a bad alternator even though all of the wear components had been replaced. It tested OK on the bench but would charge in the car and... no idiot lights.

Try grounding the small red wire that goes to the alternator, your idiot lights should go on when you ground it. This is how you test the exciter circuit.

Its all in the thread above.
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Matt

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'90 245 285k, '93 945 296k

Thanks Matt but my idiot lights don't come on with D+ grounded.

do you have 12V between ground and the D+ wire?

try running 12V directly from the + battery post to the D+ terminal and see if the alternator starts putting out the 14.5~ish volts. If that works then it would seem you have a problem in the exciter circuit that comes from the dash. have you checked all fuses and relays?

you should be able to get some help here:
http://www.volvowiringdiagrams.com/?dir=
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'90 245 285k, '93 945 296k

Uncle LoveMy240Wagon,

Please try the links to the awesome, if outstanding, Brickboard 700-900 FAQ:

www.brickboard.com/FAQ/700-900/ElectricalStarting.htm

and

http://www.brickboard.com/FAQ/700-900/ElectricalInstruments.htm

and

http://www.brickboard.com/FAQ/700-900/ElectricalCircuitsRelays.htm

and

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Hope that hepkats. (Helps yet the kats refer to kitty-kats that help by keeping those places warm with their fuzzy, furry, purring kitti-ness by being where your work is. Please read the Dr. Fox pet companion syndicated newspaper column for better care of your fuzzy kitty-kat and other pet companions.)

Off to finish the well overdue front suspension on the 1990 240 DL li'l red (and white) Kombi or Estate or Wagon as you like, with M47 II transmission and huge heart for another abused Volvo 240.)

Happy Friday Everybody and your lovely, cuddly, li'l RWD Volvos!!!!!! Give them love while working with those tools!

Hope that helps.

cheers,

Volvo "Buttermilk" MacDuffed (Well stocked up on the dairy and huge bin of loose leaf Earl Grey tea with lots a of oil de Bergamot.)
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I have no kitty pet companion. It'd be a Cobby orange tabby kitty and another Cobby silver-grey tabby kitty. Hopefully both kitty-litter-sisters.

Very helpful info however I'm wondering if there is some clue in the fact that all of my idiot lights are out (except upshift and SRS). What I have read is that only 4 of the idiot lights are part of the excitation circuit.

At this point that may not matter much as I have discovered that the PO must have encountered an excitation circuit issue and installed his own wiring rather than repair the factory wiring.

So I've got the factory D+ w/ 9V and the "aftermarket" D+ with 12V with the key on.

With the aftermarket D+ connected to the alternator and the engine running, I measured 14.4V across the alternator terminals. However, only 13.5V across the battery terminals under those same conditions. Seems like I should have 14.4V across the battery terminals, must have a wire issue between the two.

Time to fix it all up and get that "aftermarket" wiring out of there.


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'89 240 wagon, '90 740 sedan, '92 740 wagon

Not sure what you mean by "across the alternator terminals"? The alternator has just the one (B+) output terminal (as well as the little D+) and are you seeing the 14.4V, or whatever it is putting out, between it and the alternator case? If your alternator case is adequately grounded to the engine block, ~14.4V between B+ and the block. And if the block is properly grounded to the battery negative post, ~14.4V again to that post.

The difference you are seeing when you check voltages sounds like resistance in the circuit somewhere, ie: a bad connection.

I assume the battery positive is securely connected at the starter, and there also the big Red cable from the alt's B+, or you would be mentioning weak starter cranking performance. Anyway, all these connections are worth checking. To be sure, you can disassemble, wire brush and reassemble.
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Bob: Son's XC70, daughter's 940, my 81 and 83 240's, 89 745 (V8) and S90. Also '77 MGB and some old motorcycles

14.4v across the B- ground terminal and B+ output terminal. I have three wires on my alternator.

Hmmm, I learned something! All the Volvo alternators I've seen - admittedly, all Bosch's, and older than your car - have the B+ for output, and grounding is via a short Blue wire to the block, fastened to one of the small case screws that hold the alt's halves together. Maybe you have a Denso alternator?

Anyway, if you put your positive voltmeter lead on the B+, then step along the path to the battery neg post with the negative lead, that should show where the voltage drop is occurring.
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Bob: Son's XC70, daughter's 940, my 81 and 83 240's, 89 745 (V8) and S90. Also '77 MGB and some old motorcycles

It's marked ND so I think it's NipponDenso but the "terminal" might just be a case bolt. The wire coming off it does not appear to be factory.

I got the alternator charging the battery now with 14.4V, I think it was just a loose D+ connection.

Now I'll have to figure out how to fix the factory wiring, get the idiot lights working and get the extra "aftermarket" wiring out of there.