Replacement alternator

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ChristoSlang
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Replacement alternator

Post by ChristoSlang » 21 Jun 2010 21:40

I've had battery charging problems ever since I purchased Chuck Norris...

His previous owner replaced both batteries the week before delivery, but I thought nothing of it at the time. Pretty soon I realised that the batteries never seemed to charge properly, except after a looooong (i.e. quite a few hours) high speed trip. Once I installed the Madman engine monitoring system I had a digital voltage readout in front of me that showed the alternator only reaching its regulated voltage at around 3000 rpm, which equates to way above the legal highway speed

Two attempts at rewiring & upgrading the alternator made no difference whatsoever. Neither did adding an additional cable between the alternator and the primary battery, replacing the drive belt, etc. etc.

When I turned the motor off after three hours or so of playing around at Mahem with the Nissan club earlier this month, Chuck refused to start again because the batteries were flat. That was the final straw and I started shopping around for a replacement alternator.

Nissan did their usual trick of telling me that there were no Patrol alternators available in stock in good old Mzansi, that a replacement would take a month to arrive and cost me two month's worth of salary. Nobody else in Pta had a 2nd-hand item for me either, so I started looking at the Lucas/Bosch/Delco route.

I knew that I would have to do some work to make it fit, so I decided to go for a BIG alternator while I was at it. A friendly & knowledgeable bloke who assisted someone else with alternator issues on the Nissan4x4 site came to my rescue. He went brochure scouring and found that Bosch had a decent unit, but no stock in the country either. Parts for that unit would have been the same story :thumbdown:

We settled on a Delco Remy 21SI unit in the end. For those who don't know - the company claims to have built magneto chargers for the first horseless carriages, was part of GM from 1918 until 1994, and renamed themselves to Remy International in 2004.
Christo (the snake man)
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2007 350Z twin-turbo coupe (Batmobile)
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Re: Replacement alternator

Post by ChristoSlang » 21 Jun 2010 21:54

So... important specs of the unit are as follows:

Maximum Speed, Continuous: 10,000 rpm, Intermittent: 12,000 rpm
Ambient Temperature Limits: -34o C to + 93o C (-30o F to +200o F
Mounting Span: Conforms to SAE J180
Rotation: Clockwise or Counterclockwise
Weight: 6.46 kg (14.2 lbs.)
Charging System Wiring: One, Two or Three-Wire Design, Optional “R” and/or “I” Terminals

The drive pulley has approximately twice the radius of the driven pulley, so it will run at twice the engine speed which is safely within the design specs. The wiring options are nice & flexible, so that won't be a problem either. Size-wise it seemed OK, even though it was a bit bigger. The only problem we foresee up-front was with the SAE J180 mounting. The standard alternator has an 8cm spacing between its mounting feet, this bloke has a 10cm spacing. It still seemed like an easy task for a Saturday, so I dusted the welding machine & angle grinder off in anticipation. When it finally arrived and I placed the new alternator next to the old one, I realised just how misleading measurements in a spec sheet could be. This thing was a monster!
002.jpeg
But it's so big!
002.jpeg (157.72 KiB) Viewed 4760 times
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Re: Replacement alternator

Post by ChristoSlang » 21 Jun 2010 22:13

The first indication of how much trouble a 5 cm increase in diameter can mean in an engine bay (even one as spacious as that of a Patrol!) came when I tried to fit the new alternator in the old one's place. Despite all the fiddling in the world, I could not get it into position without removing the top water pipe and the alternator's tensioning bracket. Then there was a wire going into a sender switch in the block below the old alternator that was too short to go around the new alternator and had to be lengthened.

Any way, back to bracket-modifying business! To ensure that the top of the alternator stayed in line with the tensioner bracket, I had to make a bracket that lowered the bottom of the new unit. It also needed to move the alternator further away from the engine block so that it would not catch anywhere. Once I saw the strength and complex shape of the existing brackets, so I decided on an adapter bracket for the bottom.

It turned out to be very simple: some bits of 5mm flat-bar welded together, drilled through, braced with another bit of flat bar welded onto it, and bolted to the alternator gave me everything I needed. A strategically place nut was welded onto the other side of the bracket to give the final 10mm of increase required for the J180 mounting distance.

Here's the final adapter bracket, bolted onto the alternator:
003.jpeg
Adapter bracket ready and painted.
003.jpeg (132.99 KiB) Viewed 4759 times
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Re: Replacement alternator

Post by ChristoSlang » 21 Jun 2010 22:28

Right... I replaced the bottom bracket (very solid item, with 4 mounting bolts!), then bolted the alternator and its adapter bracket onto that. So far, so good! But when I replaced the top tensioner bracket, it bumped against the alternator body :think:

Again opting to retain old brackets and keep things simple, I experimented with by putting some sturdy washers behind the lower bolt of the bracket. This ended up giving me just that bit of lift (about 1 cm) I needed at the top. It did require the use of a longer bolt so that it still grabbed enough thread inside the engine block:
005.jpeg
Spacer washers hiding between lower shiny bolt and engine block...
005.jpeg (108.11 KiB) Viewed 4759 times
My adapter bracket pushed the alternator's body just far enough away from the engine that its centre shaft remained in the same place. That meant that my existing belt could be re-used. But the previous sparky has replaced it with a shorter one ("The belt was too large so it was sliding, and therefore your alternator was not charging properly!"), so I had to revert back to an original size one. :doh:

That meant removing the power steering pump's belt first, slipping it over the viscous fan blades (one by one) followed by the alternator's belt (same lengthy story). Then putting the new ones on again. I used some horrible words that my wife luckily did not hear!
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Re: Replacement alternator

Post by ChristoSlang » 21 Jun 2010 22:54

Now I just needed to get the wiring sorted out...

The existing connections to the alternator consists of a fat positive connection supplying an output voltage to the batteries, a thinner earth (actually two wires on my vehicle) that is connected to the alternator's body, and a multi-plug with two wires.

One of these two wires receives a positive via the ignition switch that is first taken through the charging light on the dashboard, then on to the indicator connection on the alternator. When the alternator is not charging, that connection is at earth voltage so the light turns on. When the alternator starts to supply a positive output voltage, this wire's +12V balances out with the +12V from the battery via the ignition switch, so the light goes out. Very elegant!

To find the correct charging indicator wire, you turn the ignition on & then connect the two wires inside the plug to earth one at a time. Do this via a smallish fuse (5A or so). If the fuse blows, you've got the wrong wire. If the charging light on the dash comes on (and the fuse does not blow), you have the correct one. I used a short piece of wire with lugs at the ends to connect the indicator wire to the proper place on the new alternator.

The other wire is for energising the rotor so that it creates a magnetic field. This is generally known as "exciting" the alternator. Since my new alternator claims to run well in "self exciting" mode, I did not bother too much with this wire. Self exciting means that it uses residual magnetism in the rotor coils to start the alternator. More on that later...

PS: If you can't be bothered to use a fuse, do not call me if you use the wrong wire initially and things breaks! The other wire does not appreciate being connected straight to earth :biggrin:

Here's the alternator all wired up:
004.jpeg
Still missing it's earth connection though...
004.jpeg (116.36 KiB) Viewed 4755 times
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Re: Replacement alternator

Post by ChristoSlang » 21 Jun 2010 23:23

So how does it all work in practice? Its graph (the 145A one) shows that it starts delivering charging current at around 1500 RPM (alternator) speed, but it says nothing of voltage, and we also have the issue of pulley sizes to contend with.
21siAlternatorPCDelcoRemy.jpg
21SI series alternator outputs
21siAlternatorPCDelcoRemy.jpg (38.13 KiB) Viewed 4754 times
I found that it does not supply any voltage at my engine's 800 RPM idle speed - voltage remains at battery supplied levels of around 12V-12.5V. Touch the fuel pedal slightly and it quickly rises to about 13V at 1000 RPM, and tops out at 13.8V (its regulated voltage) at anything over 1250 RPM. So it starts at very low engine revs, even in self exciting mode...

When the engine is spinning at a lowly 1750 RPM I can turn on the brights, all 6x spotlights and the air-conditioner and the voltage will not drop under 13.6V. This alternator can handle heavy loads without breaking a sweat! :woo:

So far I have come across only one drawback. Because it originates from Yank-land, the alternator uses imperial size bolts in places. Not on the pulley tightening bolt though, but on the rear connection terminals and on the bolts that hold it together. Because I don't have a socket in the latter's size, the alternator is currently only earthed via its mounting brackets, which in turn are earthed by the strap that connects the engine block to the chassis. As soon as I can. I'll add an additional earth between the alternator body and the chassis as soon as I can to ensure optimal current flow & guard against problems should the other earth fail.

I've not mentioned cost so far, but that's probably important too... :rolling:

The alternator and its pulley (you order the one you need - mine was 2V so I stayed with that configuration) cost me just on the wrong side of R2000. As far as I'm concerned, that's an absolute bargain for such a heavy duty alternator...
Christo (the snake man)
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2007 350Z twin-turbo coupe (Batmobile)
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Re: Replacement alternator

Post by JG Shields » 22 Jun 2010 07:18

Ek's baie bly jy het reggekom Christo. Mooi gedoen en dankie vir die beskrywing.
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Re: Replacement alternator

Post by Russ Kellermann » 22 Jun 2010 09:03

Great thread. Well done
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Re: Replacement alternator

Post by Stefan » 22 Jun 2010 11:37

Fantastic piece of work and a great write-up, Thanks Christo!! :clap:

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Re: Replacement alternator

Post by TheSourcerer » 22 Jun 2010 15:35

Well done Christo.
Glad to have been of assistance
Alan :biggrin:

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