Alternator pushing too much voltage

I drove a 30min roundtrip and I didn't see that the voltmeter was in the red zone, so apparently I cooked my original battery because the next morning it read 2.2v in my multimeter.
It was just a 50Ah 440CCA battery, so it's not a great loss, and I bought a new -proper- Bosch 74Ah 680CCA one.

Now, onto the CAUSE of this battery cooking: The alt is pushing too much voltage.
At first, when I installed the new battery to restart and check everything, it was pushing 18.5v right away at idle.
That same day at night it was pushing the proper ~14v at idle, but it would go up with the rpms, as high as 19v.
I turned the engine off and turned on the lights until the battery read 12.4v and then disconnected it from the car. It's been sitting like that while I was trying to ascertain if I need a new alternator or the problem is solvable any other way.
Tried just now again: Connected the battery on a (very) cold car, engine on, voltmeter right to 18v again.

So here's the question: Could that problem be caused by a bad alternator ground or any other cable related issue?

- If it could be cable related, I might try and clean all connections first, then install an extra ground.
- If it cannot be cable related I'll see to either rebuild or substitute the alternator (finding a new Delco CS130 here in Spain is going to be a PAIN). Rebuild kits can be found at a reasonable price on eBay... except for the shipping and taxes, that is.

Thanks for your expertise on this.

Replacing the voltage regulator is doable but not easy. Either Rock Auto in the states or Mike and Franks in Germany are your best bet.

Many of the Chevrolet trucks had exactly the same alternator in the late 80's (88 for certain). Some with a slighter higher amp rating. The Chevrolet CS is usually cheaper than the XJ CS even though they are pretty much identical. Just make sure the alternator comes with the pulley and the groove count on the pulley is the same. If the connector is different no big deal. There are tiny letter codes molded into/near the socket on the CS. Just match the "Letters" on a different hookup.http://www.pirate4x4.com/tech/billavista/Wiring/Part2/#common

Getting a new (rebuilt) alternator from Mike and Franks or ASP Eberle would likely be easier, EU no customs. But Rock Auto figures customs duties into the shipping price and is likely to be cheaper.

If you don't have the cash, PM me and I'll send you a new regulator for a fair price. The down side is you never really know if the diode pack was damaged from the voltage spike and by the time you rebuild half of the alternator you are better off buying a complete rebuild.

You can call ASP Eberle, they have a lot of stuff not on Ebay or their online store. They speak English usually.

Mike and Franks usually has better quality parts, they usually only speak German. They do understand part numbers though.

If the dashboard gauge shows 9 volts, suspect a faulty alternator, usually worn/sticky brushes. If the dashboard gauge shows 19 volts, suspect poor quality connections that are loose, dirty/rusty, corroded, and/or otherwise damaged. The battery terminals and the battery wire clamps should be bright and tight. Gray color clamps or terminals are corroded. Inspect battery and alternator wires for internal corrosion.

Thanks 8Mud. I agree that a full rebuild is the way to go once decided to open the alternator. I'll check what those companies have to offer.

Tim, I'm pretty sure that Positive cables and terminals are good up top, but I haven't checked yet the connections from the alternator itself. The reading from the alternator and battery match almost perfectly so I'm discarding any loss from the positive output of the alt. Readings at the starter relay are also consistent.
I have yet to check the PLIS connector and the grounding of the alternator, so I'll start with those if there's a chance they are the culprit.

Maybe I need to go back and read up on the CS alternator, I really don't know where/which voltage source is used by the regulator. I always thought the ignition "in" wire was just a switch to open the field winding circuit and it regulated on the output voltage. But that is just a guess/assumption.

I remember reading that around 18 volts is a fail safe designed into the CS, as a failure mode. I'm not sure if a serious power drain (partial short) can cause this or not.

One thing you can try is switching your meter to AC instead of DC. Depending on the meter, a failed diode can show up as AC voltage. AC voltage can spoof your meter in DC mode.

I have seen a really failed regulator allow the voltage to go up high enough (above thirty volts) to burn out taillight bulbs and other electrical. Not the kind of thing you want to try and ignore.

ASP Eberle is the fastest shipping, they pride themselves on being quick. Call and ask, they ship express.

Chevrolet, Vauxall, Opel are pretty common throughout Europe. A local (to you) auto electric shop may have what you need and not even know it.

The cone adapter to mount a rib type pulley instead of a V belt pulley is also fairly common kit. If you have to get creative in your sourcing.

The prices of some rebuilds here in Europe can be pretty obscene. $300 for a rebuild is kind of usury. If you have a couple of weeks Rockauto is your best bet, even with the customs duty the price will be half for a new, not rebuilt, unit (Bosch or Remy).

8Mud said:

Maybe I need to go back and read up on the CS alternator, I really don't know where/which voltage source is used by the regulator. I always thought the ignition "in" wire was just a switch to open the field winding circuit and it regulated on the output voltage. But that is just a guess/assumption.

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From what I know "I" is just an exciter. The other connected cable is L, which goes to a lamp indicator.
If it has to adjust anything it has to be wired internally to be able to read it.

I remember reading that around 18 volts is a fail safe designed into the CS, as a failure mode. I'm not sure if a serious power drain (partial short) can cause this or not.

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I read that too. A reading of 18v was an indicator of a failure. However the reading at the battery is also 18v, so it's not just a gauge thing.

The prices of some rebuilds here in Europe can be pretty obscene. $300 for a rebuild is kind of usury. If you have a couple of weeks Rockauto is your best bet, even with the customs duty the price will be half for a new, not rebuilt, unit (Bosch or Remy).

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I'm not in a hurry, so I might try Rockauto instead. I admit euro prices are scary not because of the overall expenditure, but because of the insulting price difference for the same hardware.

Thanks a lot

Back again.

I tried today to hook an extra ground for my current alternator and it didn't solve the problem. I'm simply going to get a new one and get it done.

8Mud, I have sourced a Crown alternator that I can find here in Spain for about 185€. Would you get that or go for a Bosch instead? I need a good working unit, but I don't need anything fancy or will be asking much of it, so maybe the -smaller- price difference with Rockauto is compensated by the fact that I could have it here in 24h.

I've never tried Crown alternators, but have used Mexican rebuilds with no issues. If you are sourcing your Crown from ASP Eberle they are good about returns. Though I'm not sure about electrical parts. I've gotten some parts shipping damaged and wrong parts from them before, they shipped a replacement quick, no problem.

For 185 Euro I'd probably go with the Crown, you can ask Mike and Franks if they will price match? They used to get better quality non OEM parts than Crown, but their quality has fallen off some recently, about the same as Crown. If you ask Mike and Franks they likely have a new Delco, it may be about the same price as the Crown if your lucky. Worth a phone call. The price fluctuates, they try to match what the competition is charging sometimes and have some deals.

185 Euro is a good price,the last time I checked they wanted a 100 Euro more than that, around 280 Euro. Which makes me wonder if that price isn't too good? Maybe there isn't much demand for the CS anymore?

If you do opt for the rebuild, save your old alternator and rebuild it. Order a set of brushes, if the bearings aren't noisy I have a new regulator and rectifier on the shelf I have no use for anymore. The regulator is fairly easy to change, the rectifier is a little more involved.

A replacement alternator and starter are two things I keep handy, along with a distributor cap, rotor and a few other parts. Especially a spare starter and a starter rebuild kit.

8Mud said:

If you do opt for the rebuild, save your old alternator and rebuild it. Order a set of brushes, if the bearings aren't noisy I have a new regulator and rectifier on the shelf I have no use for anymore. The regulator is fairly easy to change, the rectifier is a little more involved.

A replacement alternator and starter are two things I keep handy, along with a distributor cap, rotor and a few other parts. Especially a spare starter and a starter rebuild kit.

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If I change it I might rebuild the old one indeed.

I've sourced the Crown alternator in-country, so I'd have it in 24h. Final price 179€ shipped. I might send an email today to Mike and Franks just in case they can price-match with a Delco unit.

I installed the Crown alternator this afternoon. Everything is back to normal, although it took some convincing to get it in
169€ ($190) for the alternator and I had it here in 24h.

Thanks for all the help and suggestions!