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Super Moderator
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Discussion Starter #1
OK - So I've be ignoring the quirky behavior of my car.
By the numbers:

Battery - early 2018 vintage. Discharged once a month after buying it (left parking lights on all day at work)
Recharged and uneventful.

Alternator was converted by previous owner in 2015 to Bosch AL49X.

A few months ago, alternator light started lighting up dimly; many tests later - battery shows a max of 12.3-12.5V after 100% charge from external charger.
A few folks commented battery may be shorted or near death.
Car had one episode of high voltage about 2 months ago - 15-16V but battery still only at 12.3V.

At idle, the voltage at battery was 13.6V

Today, car was running OK. Then again the high voltage (confirmed with cigarette lighter Voltage meter - 15V seen at 3K RPM).
Turned off engine - took out multimeter and battery reads 12.1V

For 100 points:

1. is the battery near death (even though it starts car) and forcing alternator to charge at high rate 15V?
2. is voltage regulator toast with its intermittent behavior?

I don't want to buy a battery only to have voltage regulator kill it. On the other hand, the shop that I usually have replacing alternator has a long 2 month backlog.

Given this is the 2nd episode, It seems like battery is culprit as the voltage is even lower now.

But (naively) hoping I just have a broken battery.

Thoughts? Opinions? SWAGs?

Thanks - Eddie
 

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Wingless Wonder
1988 Esprit Turbo
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Which wires did you jiggle 2 months ago? Assume you have investigated them, again.
 

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Discussion Starter #3
Subscribed.

Which wires did you jiggle 2 months ago? Assume you have investigated them, again.
Picture below - just measured battery again - 12.26V According to previous info, this is far away from 6x2.2v per cell or 13.6V fully charged.
But car still starts - is the battery dead or alternator voltage regulator dead?

1272260
 

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Dreaded Prior Owner
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Battery at rest with 12.8V is good, Don't think you'll see 13.6V unless the alternator is charging. My AL49X seems to sit at about 13.7-13.8V when running. I'd be looking at the alternator voltage regulator if volts are ever 15+ and the wire to the starter post/battery is tight. I think your regulator/brush holder (@10:00 below) mounts from the outside with just two screws if you can find the right one.
You may have to reverse search from the BMW model these originally fit in order to find the right regulator.

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1272272
 

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Dreaded Prior Owner
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A possibility, but check the part number on your regulator. My pics are out of focus but mine might be a 1 197 311 027
 

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I'd pull the battery and take it somewhere that will do a load test (Autozone will usually do it for free). I suspect it's good but that should remove all doubt. Next double check that all the connections on the alternator are clean and tight. Finally if you still have issues replace the voltage regulator. It's held in with two screws (it's the part with the black power transistor in Snowrx's photo). You should be able to find them through Bosch and shouldn't be too expensive.
 

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First step is to fully charge the battery with a battery charger. Then get it load tested. Replace if it fails. Once you have a good battery you can properly test the alternator. Or you can remove the alternator and have it bench tested. The battery affects the alternator and the alternator affects the battery so you must test them BOTH individually. While charging and testing the battery you inspect it for signs of bulging, leaking and corrosion. Clean the terminals. When examining the alternator you check the belt for condition and tension, and the alternator for any sticky goo. Replace the belt if questionable, the voltage regulator if it tests bad, or you see sticky, black goo.Draining a battery past 50% can shorten it's life drastically. Do it more than once and it is deadly.
David Teitelbaum
 

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I think he's safe on the sticky goo worry. He has the Bosch 49ALX so no goo, and better still the Bosch alternator has an easily removable regulator.
 

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Project Addicted
1984 Turbo Esprit
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Your over-voltage alternator, if it really is putting out in excess of 15v at time probably killed your battery. Generally, a car alternator should not exceed 14.5v when charging a discharged battery. The voltage regulator should not allow a higher voltage, especially nothing near 16v.

You can have the system load tested to see what max output is, Amp and Volts at many shops. They just need a good system tester that they can hook to the battery and measure.

Just my .002
 

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Wingless Wonder
1988 Esprit Turbo
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The one car I had with a bad voltage regulator literally BOILED the battery electrolyte out of the battery when it overcharged! o_O
😱
Generally, a car alternator should not exceed 14.5v when charging a discharged battery. The voltage regulator should not allow a higher voltage, especially nothing near 16v.
^^^ True, Dat!
 

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Once you have smelled a "boiled" battery you never forget that smell. Like boiled coolant or blown clutch or hot automatic trans fluid. My father had a '36 Cord and they put the 6 volt battery under the driver's seat. When it overcharged, the interior of the car reeked and it dissolved the seat frame. That car had the battery with the caps you took off and filled the battery with distilled water. It had a generator with an external black box that regulated the voltage when the motor was going fast enough to actually make the generator spin fast enough to create some electric. Not only is overvoltage bad, a blown diode bridge in the alternator will pump AC into the battery and that can kill it even faster than too much voltage. Overvoltage will also blow out your light bulbs and damage the sensitive electronics.
David Teitelbaum
 

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Dreaded Prior Owner
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It will take a bit of time to damage (heat/boil) the battery at 15 volts, so if you were monitoring and caught it it's probably OK with regard to that. I've had poorly regulated battery chargers kill a few batteries by going to 16V for too long.

I'm in the process of adding cheap digital voltmeters to my chargers so I can monitor them as they charge.
 

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Wingless Wonder
1988 Esprit Turbo
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Overvoltage will also blow out your light bulbs and damage the sensitive electronics.
LOL, he said sensitive electronics when referring to a G-Esprit! :LOL::LOL::LOL:
 

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This may sound simplistic but if you are sure the problem is not in the wiring and your only two choices are the battery or the alternator as the problem then why not change them both. Neither is too difficult a task and you buy about another 5 years of peace of mind. Sure it is the "shotgun" approach but when the shotgun hits all of the suspected problems at once for a not too high a cost it may be worth the shot.
 

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Discussion Starter #15 (Edited)
This may sound simplistic but if you are sure the problem is not in the wiring and your only two choices are the battery or the alternator as the problem then why not change them both. Neither is too difficult a task and you buy about another 5 years of peace of mind. Sure it is the "shotgun" approach but when the shotgun hits all of the suspected problems at once for a not too high a cost it may be worth the shot.
I am leaning this way; I will recheck with shop what their lead time currently is (Update: earliest is Nov 15) and have them replace the voltage regulator. And the battery does seem damaged so doesn’t make sense to risk destroying a new battery.


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Discussion Starter #16
carbuff> LOL, he said sensitive electronics when referring to a G-Esprit! :LOL::LOL::LOL:

I'm a conservative fella - I also have a New in Wrap Bosch CIS 'computer' just in case. In it for as long as I can drive it.
 

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Wingless Wonder
1988 Esprit Turbo
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I also have a New in Wrap Bosch CIS 'computer' just in case.
Just be gentle with that thing! You don't want to lose any of the beads from the abacus incorporated, inside. :p
 

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Discussion Starter #18
Decided to replace entire alternator. Concerned the high voltage might be beyond the voltage regulator. And the tag on the rebuilt Bosch AL49X cautions about hooking up to a bad battery. Going to spring for a new battery too. Thanks for everyone’s input!



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Dreaded Prior Owner
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Curious; what's the part number on the new alternators regulator?
 

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Discussion Starter #20
Voltage regulator Bosch 1 197 311 028. Bought from FCP Euro - OK price and lowest core charge. Preferred spending $161 for Bosch rebuilt vs $98 for unknown brand rebuilt at Oreilly’s.




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