[Vwdiesel] Wiring a VW alt in tandem with another

Tue Dec 4 20:33:09 PST 2012

Well-it is a 25 amp 300 watt cab heater. I know it isn't much and I am looking to upgrade that as well-one thing at a time.

From: tadc at europa.com
Date: Tue, 4 Dec 2012 20:27:35 -0800
Subject: Re: [Vwdiesel] Wiring a VW alt in tandem with another
To: tgott at hotmail.com
CC: vwdiesel at vwfans.com

Boy, that electric heater must be pretty worthless running off that small alternator.
You shouldn't have any problem grounding both systems to the chassis, assuming that all grounds are good grounds (i.e. you don't have two parts of the chassis that don't have a good connection between them).  

On Tue, Dec 4, 2012 at 6:13 PM, Travis . <tgott at hotmail.com> wrote:

The reason I am/was considering the system in parallel is the JD alt will be maxing out with both PTO's running, the tractor lights, the fuel solinoid and the fuel pump along with charging after starting/glow plugs. They didn't have the room to put the larger alt on like the JD 430 L&G tractor has under the side covers. The cab came off a JD 420 L&G tractor which was an air cooled engine with a stator and voltage regulator (Onan engine). My 332 has an alternator which is like a stator with a couple of magnets glued to the housing and then a 5 pin VR it connects to. I may be able to lower the voltage on the regulator by putting in a relay on the green sensing wire that tells the VR what to output at as that is a known issue. Back to the 420-it had a GM alt hooked up to a gear drive rear 2000 RPM PTO and they also had a salter spreader and a battery and a rats nest for wiring. There was a positive wire coming off the tractors battery and it looks like that may have driven some

 things while the rear battery/alt drove other things like the salter and cab heater and cab lights. I think the wiper, stob light, doom light and fan were driven off the tractors battery. The GM alt isn't pretty with the years of salt hitting it but I assume it works. My rear PTO I want to use runs a belt drive to a hyd pump that then drives a tiller (JD 30 Hyd tiller). So I figured I have a nice looking almost new VW alt, the salt spreader is NOT getting installed and I have a rear JD weight box to put a VW battery. I was trying to copy the 420 best I could but I don't think I should after digging in more. The 420 did come with another new voltage regulator so I am wondering if they had had battery problems before on the tractor with not enough charge for the draw they were using-it only had 601 hours.

So-keep the systems separate then and just keep an eye on the tractors battery to see if it is draining. Is there any problem with both systems grounding on the frame just as long as the two positive sources aren't in tandem? There is a lot of things I don't think I could get by with not grounding to the frame like the strob light (which wasn't working due to a bad rivots not grounding).

I will run the alt charging wires to the battery then up to the cab with a switched main line and I will run off that switch another line back to the alt exciteder with a light inbetween and the electronics can run off that main feed line from the battery. Anyone see any problems with that?

I love turning wrenches as I can visually see what is going on-but electronics scare me as you can't see electricity and the things it runs-isn't cheap and it can be hooked up wrong easier then most mechanical components and depending on the voltage/amps it can also be more deadly as I can see a mechanical thing vs the electricity.

Thanks for the help everyone. I need to get some toggle switches now. The OEM Cozy cab has 8 pre-drilled holes for toggle switches/lights and a 7 slot fuze pannel with leads on both ends of the powered side. I want to make it look nice and not add more holes and get rid of a few of the added cords (no just wires but cords). The cab has a window wiper, fan, electric heater, 3 cab lights, strob light and doom light. I am also running and electric shoot discharge control. If I can figure out how to properly string heater hose without drilling holes I will also change the electric heater to a coolant heater.

Travis

> Since the JD alt charges at 15V it's going to be working pretty hard since the VW alts tend to charge in the high 13's to low 14's. You could use a separate battery for your cab/pto system, even if it's a small motorcycle or lawn tractor battery. Not sure how well they share the load when regulated at different voltages. Might be time for Roger to comment! :-)

> Loren

>

> So if they're wired in parallel, what's the need for an additional battery?

>

> If there are two alternators regulated at different voltages, I would

> expect (disregarding voltage drop in the wiring/junctions) the JD alt would

> be doing all the work and the VW alt would be loafing, at least until the

> JD is maxed out on amps and its output voltage starts to drop. This gets

> back to your comment about frying the JD regulator.

>

> FWIW, a personal anecdote re: "running an alternator without a battery will

> destroy the alternator", when I was young(er) and stupid(er), I swapped

> batteries in my POS AMC Concord with the engine running... I think because

> the "new" battery was dead and I didn't have jumper cables? Don't really

> remember, but the point is I was able to start the car, remove the old

> battery and install the new one with no apparent ill effect to the

> alternator, so maybe that conventional wisdom should be amended to

> "...*eventually* destroy the alternator." :)

>

>

> Wouldn't be wired in parallel then. VW would have a battery it's wired to (either one could go to the D+) and the JD would go to the normal battery. That way the VW alt can generate away, at it's voltage and the JD do likewise, both on basically separate systems thusly not interfering with the operation of the other with the simple addition of a small (or not so small) battery.

> Loren

>

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