NissanDiesel Forums

I got the alt today. It has no vacuum pump shaft. Is there a chance I can bodge together the 2 and make a running alt. or must I return it?

Is the SD22 in a forklift missing this vacuum pump and therefore uses a different alt? According to the listing this is a forklift part. This sucks.

Christian

Forklifts don't need vacuum.

You could take the rotor, rear housing (including bearing & shaft seal) from the old alternator and use it on the new one, but . . .

You don't want to disturb the shaft seal without replacing it, and when you replace it you will want to use a spacer behind the seal to place the seal's lip on a different place on the rotor's shaft, because the seal wears a groove into the shaft and a new seal may not seal on the worn area. Leakage = oil in the alternator where it doesn't belong.

Also, transferring the VR to the old housing isn't fun.
(See also my Hitachi LR150 alternator post)

SD alternator housing pics:
(click on any image for larger)

Inside view of rear housing



Outside view of rear of housing
,

Alternator rotor
,

Inside of rear housing, stator, VR, brush holder, assembled view
.

Transferring the VR, brush holder, and stator/diode assy (they're all soldered to each other) takes patience. However, if you take good notes and are willing to spend a couple hours at it, you can do it. If your old rotor is good, and you get a new shaft seal first. Don't bother if you don't have the seal, you'll be sorry.

Because I think your alt's problem is with the diode assy and VR, and because the new alternator's probably got working ones (if not new, at least tested), you are 2/3s of the way there with what you have.

stator with new diode assy. soldered on
.

My SD alternator "test bench"
.

.

Al,

Awesome pics. I love the bench. I can solder with my teeth in the dark (5 years on the road as soundguy for a country band) so I think I am going to try it. The price is right Is the seal in question the one down in the assembly of the fourth picture? Do you have a good source for this seal? Dealership?

Gracias, huge gracias.

I do not have a good country-wide source for the rear seal, but its dimensions look to be: 15x32x7.5(or 8)mm, as shown in the pic.



There's also some handwritten part nos. on the package: 41-81700-1, which got me nowhere when I tried to get them via that number.

I have a local rebuilder who supplies me with that seal for about $6. Armed with those dimensions, you might be able to source one via a seal supplier.

[later]
My local guy has one in stock, $6. Oh, it's a double-lip seal too, which isn't OEM.

You'll need the low-heat pencil for the five or six VR connections and the brush leads (though you'll just use the new brush assy. I imagine), and a much higher cap iron for the diode assy connections. I was able to do the latter with a std 140W Weller, I think, less heat than I thought it'd take.

Do a real good job at documenting how the parts in that rear housing come out: spacers, bridges, studs. Coming from Delcos, it was a nightmare for me, the first one I did several years ago.

asavage wrote:SNIP- (oil seal) 15x32x7.5 -SNIP

You'll need the low-heat pencil for the five or six VR connections and the brush leads (though you'll just use the new brush assy. -SNIP

I wish I had taken photos when I replaced my brushes. I used a pair of hemostats to keep the brush spring retracted on the brush cable while I soldered the L tab from the OEM brush to the replacement brush.

Otherwise, my alternator is still all original.

But I'm going to get one of those seals ... just to have on hand.

Update:

I learned a valuable lesson today. I tore down the new alt for parts before removing the old one from the truck. Not even remotely close. The new one is 3/4 the size of the old one. There is no VR in the new one. I guess I am taking the original to the rebuilder. I have a lot of pics. I'll post the highlights soon. Let me just say "oil bath" pretty well describes the condition of the insides.

Make certain your rebuilder knows about the diesel alternator/vacuum pump/oil seal issue. Don't assume.

Copy that. Do you have an exploded view of the vacuum pump assembly?

Back half of the exploded view at the top of this post . . . whoops, no it's not. That view doesn't even show the shaft seal which is installed in the alternator's rear housing, not in the vacuum pump, which is why you need a good o-ring between the vac pump housing and the alternator's rear housing: it's an additional leak area, though I've never seen one leak there.

Yes, I have the exploded view: it's in the Brakes section of every FSM, and I have just about every 720 FSM (except, right now, 1982: I sold mine to a member who didn't want to wait for one from eBay). However, I don't have the Brakes section scanned.

If you don't have a FSM, you have got to get one. It's not optional: you can't diagnose or repair the DPC or GP systems without it. Check out this eBay auction and go get one!

I got a 1982 manual. Yesterday I didn't see the pump in it. I didn't look in brakes. Got it now. Speaking of O-ring failure at the rear of the alt, I had leaks there.

cseger1 wrote:Speaking of O-ring failure at the rear of the alt, I had leaks there.

If you figure out the size of that o-ring, please pass it along.

If any of you have one of these alternators out handy, what are these eye-to-eye, flange to flange dimensions? I'm workin' on a substitute. Thanks.

Lower mounting ears (inside) = 3-3/16"
Lower pivot to upper adjuster bolt CL = 7" (+- 1/8")

not trying to hijack the thread, but Toyota 2L diesel engines use a similar alternator. The 2L engine I pulled at the JY also has an alternator driven vac pump. We should compare these units.

sa

Is the Vac pump on the back of the Alt used for anything else besides brake assist? And is the voltage regulator built into the Alt or external?