Dash Battery Light Woes. Trying my best

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SamsBus2012
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Re: Dash Battery Light Woes. Trying my best

Post by SamsBus2012 »

I have this issue. I am convinced this is with the alternator - in my case, the internal connection to the D post on the alternator is poor - I get 14.2 at the B and around 9.5 to 10 at the D - result constant slight glow of the batter light on the dash. Solution is probably to split the alternator casing and tidy up the contact on the d post (or live with it). Sorry if this sounds flippant but it's what has worked for me.
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marlinowner
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Re: Dash Battery Light Woes. Trying my best

Post by marlinowner »

The problem(s) will be in the alternator, but its not going to be a simple bad contact. The two alternator terminals aren't connected directly together, they are linked through the diodes. Most likely that's where the fault is.
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Re: Dash Battery Light Woes. Trying my best

Post by bmouthboyo »

OK thanks for the heads up.

Is it normal for my battery to read low 12v / high 11v after 5 minutes idling? What would cause the alternator to drop it's output like that?
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Re: Dash Battery Light Woes. Trying my best

Post by marlinowner »

My understanding is that the voltage regulator works by modulating the current through the field coil (rotor), but the field coil is connected to the same diode output as the D post, so if the voltage is low here then the field coil voltage will be low as well - maybe this will lead to low output voltage from the alternator.
ie I think both the glowing bulb and low output voltage are due to the same problem within the alternator.
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1981/1968 Marlin Kitcar TR6 Engine

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Re: Dash Battery Light Woes. Trying my best

Post by bmouthboyo »

So today on my way to a Grearbox workshop I broke down, voltage guage I have at the dash was slowly showing less and less volts, powersteering stopped and I guess fuel pump as a rolled to a halt. Wouldnt crank.

Garage guy bought a charged battery as I was only a mile away and it fired straight up, still having the battery / alternator light warning light on.

I guess the alternator is not consistently outputting high enough voltage. As previously mentioned I tested the blue wire coming from the alternator and it was only around 9v so is it fair to assume this is the issue?

Next question is does this kind of fault sound worth while getting the Alternator serviced? or dig into my pockets for a new one?
1983 Autosleeper Trooper - 1.8 Gti Conversion

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Re: Dash Battery Light Woes. Trying my best

Post by CovKid »

Get it rebuilt (either third-party or yourself). Its too often assumed that regulator replacement is the cure-all. It can be, but theres also a diode pack in there which converts AC to DC and they can fail too. You can buy them and fit them yourself but you need a big vice for sure. Lots of videos on youtube on how to swap out the diode pack - if you're up for having a try. Alternators are not cheap (like starters) but they can be rebuilt at home for relatively low cost. I always rebuild my own. Its rare that the windings fail, although not impossible. Bearings tend to fail way before they do.
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Re: Dash Battery Light Woes. Trying my best

Post by California Dreamin »

Agreed Ralph, if you can find a company to supply the parts (usually commercial supply only but there is no reason why an auto electrical outlet wouldn't retail supply) you might also want to replace the slip ring (the contact for your brushes which tends to wear quite badly) and check front and rear case bearings (these do have a tendency for the rear bearing outer race to wear the rear casing , so check..
Or .. look for an Auto Electrical (starter/alternator) business in your area, get a quote to recon...comes with a guarantee.

Martin
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Re: Dash Battery Light Woes. Trying my best

Post by CovKid »

Plus most of the parts can be found on ebay. Once you have the relevant part in front of you its not too difficult to hunt for a match.

As an aside, some years ago the wiper motor on my beetle failed and even in the 1980s VW wanted a whopping £80 for a new one and they didn't supply brushes either (which is what had actually failed) as they regarded it as a sealed unit. After some thought, I went to a lawnmower shop, found a very close match, which only needed slight sanding to make them fit. Total cost - 15p :D

If you do go for a replacement alternator, always try to keep hold of the old one and take it apart - you'll learn much. Rarely have I come across a seemingly dead starter or alternator that can't be brought back to life. The fault is often really easy to fix. The earlier golf alternators can be a good match, usually only needing a pulley wheel swap. In all other respects they're the same unit.
Roller paint your camper at home: http://roller.epizy.com/55554/" onclick="window.open(this.href);return false; for MP4 download.

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