borland

Anyone try this alternator regulator mod to increase the charging voltage:

http://electric.articles.mbz.org/regulator/

borland
90' S4, Slate Metallic

jeff jackson

Now that is some very interesting reading. I wonder if the voltage increase puts additional wear and tear on the regulator...I wouldn't think anything other than a "bearing problem" or overtensioned belt, would cause a premature failure of the alternator itself. But this diode mod, could it cause the regulator to "burn out" prematurely ??? If not...its a viable solution, for all of us that have added significant electrical loads to the OEM charging system. Like Alarms...Subwoofer and stereo amps...DVD/ Navigation...Radar Detector. etc.etc.

T_MaX

Sounds like it should work!

A good mod for those who are using high power lights or aftermarket sterio amps!

Bill Ball

Hmmm... I've seen low voltage since I installed a 300 watt RMS amp. At idle with the lights on, the indicated voltage can fall below 11 and things get dimmer. As soon as I raise the revs even a smidgen from idle, it jumps to 13+. Would this really help at idle? Seems like simple change, and if the diode failed, it would just go back to ground, right?

jeff jackson

Bill...bite the bullet and buy one of the "rebuilt" alternators off ebay...do the mod, and let us know how you like it...that way, if there was any trouble, you could just switch back to the OEM unit, and be none the worse for the test.( I hope)...I too, have an aftermarket Alpine amp...Infinity Basslink unit, Valentine 1, and Viper Alarm / Remote start system...and am dismayed by the voltmeter reading at idle, particularly if the headlights / foglights are on, as well..

borland

The regulator only excites the stator with additional low current. The example car in the link is similar to the 928, in that the battery is quite far from the alternator. If you measure the output from the alternator under the hood, and again at the battery, there will be a noticable voltage drop.

One thing I noticed, is the alternator pulley on my 90' S4, is a smaller diameter than what's supplied with the OEM or aftermarket alternators, which call for a Bosch AL170X. Also, they don't come with a required shim between the fan and the pulley making the belt ride further out from the alternator housing. You have to look at the PET parts database to see these parts listed.

Most parts catalogs list the same Bosch part number for my 90' S4, and say also used on Porsche 944, 951, and 968.

So, if your alternator was ever replaced with a rebuilt, then its possible you have the wrong pulley setup (i.e., too large a pulley making the alternator run slower at idle, not to mention belt alignment with the crankshaft pulley).

Bill Ball

Well, Jeff, if I have chance to get to this, I'll be glad to be the guinea pig. It seems rather harmless and easily reversible, so I'll just do it on the stock alternator.

heinrich

Nice ... I'll go buy a diode, but when I'll get in there ... may take a while.

borland

Here's a writeup on taking apart a Bosch alternator. Wrong model, configuration slightly different, but some similarities to the 928's Bosch. Some mis-information, but good photos.

http://www.rangerovers.net/repairdet...haltrepair.htm

Bill Ball

Cool. I might as well rebuild the old girl while I'm in there.

Weissach

I have the adjustable regulator on my car. I got it from Iceshark(from the 944 forum on rennlist). It works great, much better than factory(14.4 amp with everything off). Do a search in the 944 section and you will find all the info you'll ever need...

jeff jackson

Hmm...thats interesting too,Sterling...what gauge wire was the OEM piece, and what size to you enlarge it to for your upgrade ? Do you remember ??

dr bob

Part of the improvement seen when replacing the battery cable is undoubtedly due to cleaning the connections. For us, the only loads coming from the battery are the starter motor and the cooling fans (ON S4+ cars). Aftermarket stereo amps wired directly to the battery would be another.

The alternator is a lot closer to the load end of the system when the car is running. Potential loss points (pun intended...) are the connection at the alternator itself, the connection at the jump-start terminal (very popular), then the feeds to the fuse panel. A good cleaning of all the primary connections and the ground points will help a lot with low voltage issues. Cleaning the big connection at the starter will help some with the low voltage at the battery when the charging current to the battery is high.

Alternators have a capability curve based on RPM's. Increasing the excitation current at low RPM's may help with the voltage, but is also likely to cause rotor heating that may lead to premature failure. Make sure you have the right size pulley, as some point out, and you'll have a better chance of maintaining voltage at low engine speeds. The crank pulley for the alternator is already pretty big, so don'y go smaller than stock on the alternator or you'll risk overspeed demolition when you accidentally take the engine to redline.

Old, weak, or undersized batteries may not have the available capacity to maintain your system voltage when the alternator capacity falls off at low engine speeds. Sometimes a new battery, with associated terminal cleaning, is all that;s needed to revive an apparently weak electrical system.

Last but should be first: Follow Wally's annual electrical maintenance recommendation to keep your electrical system reliable. Voltage drop in a system is the sum of all the drops in any given circuit. That includes all the cables, connections, ground points, ground straps and cables, plus fuses and loads. Most electrical reliability problems in our cars can be avoided by following Wally's excellent maintenance recommendations.

heinrich

Bob, same difference

Bill Ball

Good points, dr Bob. I should do that first.

Sterling - You used 0 gauge marine wire, right? Stock is 4, right?