Having trouble finding someone to test alternator

[Baltimore Sailor]

I stopped by the Auto Zone to see if they could check out the Motorola 35-amp alternator off my engine, but they said they couldn't do it because they didn't have a matching pigtail for the exciter lead off the alternator.

Before I start chasing all over the place, does anyone know of a place in the Frederick, MD - Baltimore area that can actually check out one of these alternators?

Thanks!

[tenders]

I think AutoZone just wants to (try) to sell you a new alternator. Try a NAPA auto parts store. The one in my neighborhood took a few days to test mine out -- I think they have an "alternator guy" who comes by every few days to test, report back, and rebuild as necessary.

[rigspelt]

Look for a specialized alternator shop. There are two in our small city who sometimes even bench test on the spot. There must be more in larger centers, unless they too are a species going extinct. One of them checked our original 35 amp Motorola when we bought the boat last year: 13.2 volts, very close to the expected 13.4-13.5 for that model, which is too low for our new electrical system, so I replaced it.

[Jesse Delanoy]

I've used a simple standard slide connector from the hardware store to make that connection. Sounds like a line of bs from Auto Zone.

[Baltimore Sailor]

That particular Auto Zone has been very helpful to me in the past, so if the guy had wrong information about how they can test alternators, I'll give him the benefit of the doubt on it.

I'll look around for an alternator shop in the Baltimore area. I can also try the Advance Auto Parts store, they might have better luck, or more knowledge.

Thanks for all the tips.

One other question: does the shop need to know how many rpms to spin the alternator? If they do, would it just be the normal 1800 rpm of the engine during cruising, or some other number?

Thanks again!

[tenders]

The engine RPMs don't necessarily correspond to the alternator RPMs. Presumably the ratio of the engine and alternator pulley diameters is designed to drive the alternator at a reasonable or typical rate.

I don't think the alternator test comes back "OK at 2300 rpms but not OK at 1500 rpms." Most electronics don't break down that way--a blown diode or shorted windings will be off at any speed.

[lat 64]

Shop guide

I just brought my alternator and starter to an old auto-electric rebuilder in Fairbanks. The guy there identified both by just glancing at them.

Here's how to spot a good shop:
You have to go to the bad part of town(industrial that is)
They don't always advertise, you need a referral. First go to a tractor, trucking or marine shop; or a smoky bar to get this.
The front door is hard to find.
If there is a pit bull at the door, try another shop.
The place will be dark and no one will be at the counter. This is ok.—they are working. you'll hear hissing and other noises of bench-top industry. There is a bell somewhere—look around for it. Don't use the bell, it's rude.
Yell "helloooooo". This will bring an old blind black Labrador retriever to the front. This is ok. you will now be served.
Give them your phone number, it's all they need(no cell, you don't want to look like a spender)
Talk mostly about the weather and casually mention it's for OLD boat that you are helping to fix up. Beyond that be honest. Admit you don't know much but heard they were a good shop. Absolutely NO politics!
No, you are NOT in a hurry.
No, they do NOT have a web site–ask for their business card. The card will be old and greasy. Don't worry you can wash up later.
You must learn how to say " have a good one" in the local dialect, and tell them you have to get back to your lame job.
This is a good time to ask for their referral to a good lunch cafe.
Get lost so they can get back to work. You have been talking to the actual person that will do the work.
Watch your step as you leave. The lab is blind remember, and he doesn't go far from the door.

good luck,

Russ

[Baltimore Sailor]

Stopped by Advance Auto Parts on the way home from work today, alternator in hand, to see if they could test it. The conversation went approximately like this:

Me: Can you check this out for me?

Lady behind counter: Sure. What kind of car is it from?

Me: It's not from a car, it's off my boat engine. But it's a standard 12-volt alternator.

Her: Hm. Looks like an old Chevy alternator. [Starts typing on her computer, brings up various alternators on the screen] Hmmmmm... OK. [Picks up the alternator and takes it back to the test station, attaches a belt to the pulley and the test station's motor, and tensions the belt.] I'll have one of the guys that usually run these tests come up front to do this for you.

[A few minutes pass, and a young dude walks up to the test station]

Him: Hi. What kind of car is this from?

Me: It's not off a car, it's off my boat engine. But it's a regular 12-volt alternator.

Him [looking gravely at my alternator]: Well, let's see... [Picks up the yellow exciter wire and looks at it curiously, saying nothing]

Me: That's the exciter wire... I don't really know what it does... it connects to the coil.

Him [brightly]: Let's hook it up and see what we can do.

[Ignores the exciter wire entirely, and attaches the positive lead to where I show him is the positive terminal and the negative lead to the body of the alternator. Pushes a button on the test station's panel and the alternator starts spinning. A needle on one of the dials swings over to the right, well short of the "green" area on the gauge. The young guy looks pleased.]

Him: Well, that did it. The alternator's no good.

Me: I knew that. Can you tell me what's wrong with it? Which diode is bad, or whatever?

Him: Oh no, this test doesn't do that. It can only tell you if the alternator is good or bad. [Takes the alternator off the test station.]

Me: Oh. OK. Well, I already knew it was bad; I thought your test would let me know if a particular diode was bad, or maybe the regulator...

Him: No, that's all I can tell you, sorry.

Me: OK, thanks.

Next stop a real alternator repair shop, I suppose. I've found a couple by Googling for them in the Baltimore area.

They're over in the industrial section of town.

[tenders]

I just brought my alternator and starter to an old auto-electric rebuilder in Fairbanks. The guy there identified both by just glancing at them.

Here's how to spot a good shop:
You have to go to the bad part of town(industrial that is)
They don't always advertise, you need a referral. First go to a tractor, trucking or marine shop; or a smoky bar to get this.
The front door is hard to find.
If there is a pit bull at the door, try another shop.
The place will be dark and no one will be at the counter. This is ok.—they are working. you'll hear hissing and other noises of bench-top industry. There is a bell somewhere—look around for it. Don't use the bell, it's rude.
Yell "helloooooo". This will bring an old blind black Labrador retriever to the front. This is ok. you will now be served.
Give them your phone number, it's all they need(no cell, you don't want to look like a spender)
Talk mostly about the weather and casually mention it's for OLD boat that you are helping to fix up. Beyond that be honest. Admit you don't know much but heard they were a good shop. Absolutely NO politics!
No, you are NOT in a hurry.
No, they do NOT have a web site–ask for their business card. The card will be old and greasy. Don't worry you can wash up later.
You must learn how to say " have a good one" in the local dialect, and tell them you have to get back to your lame job.
This is a good time to ask for their referral to a good lunch cafe.
Get lost so they can get back to work. You have been talking to the actual person that will do the work.
Watch your step as you leave. The lab is blind remember, and he doesn't go far from the door.

good luck,

Russ

This is brilliant and 95% descriptive (no dog) of my recent experience at a place called Bronx Alternator. (When I was told by my referrer that I should "try Bronx Alternator" I thought he was jokingly suggesting that I steal somebody else's alternator.) I gave them my alternator and my phone number and received only a brief lecture not to wait weeks to pick up the fixed alternator.

[rigspelt]

Next stop a real alternator repair shop, I suppose. I've found a couple by Googling for them in the Baltimore area.
They're over in the industrial section of town.

Take a carboard tray of coffees from the nearby takeout. And a dog biscuit - but ask first if the dog can have it.

[rigspelt]

... check out the Motorola 35-amp alternator off my engine, but they said they couldn't do it because they didn't have a matching pigtail for the exciter lead off the alternator.

For what this is worth, last year I spent a few hours googling the (apparently) original 35 amp Motorola that came with this old boat back when we got it. I cannot verify any of the following info, which comes from personal notes I made as I googled. I have since replaced that alternator with an MMI 55 amp, so had no need to press on to sort it out, but maybe these bits will help you somehow. The label on this one reads Motorola 12V, Model MR12N451D, Serial 19893, Type B, N Ground, 35 Amp.
---
Apparently these alternators were common as sidewalks.

Ours appears to have a Transpo external alternator attached to it, probably aftermarket at some point in the past 35 years. Lo and behold I found the regulator described on this page:

http://195.125.241.148/cgi-win/product.exe?M5197A

Transpo M5-197A REG MO 12V
replacing OE MOTOROLA 105-197 5-197 8 RG 2010A
Voltage Set Point: 15.0 V
Regulation: B-Circuit
Adjustable Voltage
Short Key Hole Case Style
Terminal Identification:
PLUG-TYPE: K
WIRING CODE 3
RED...................ISOLATION DIODE(+)
BLACK .............GROUND
GREEN..............FIELD
YELLOW...........IGNITION

A webpage said "An alternator date code was typically stamped at the back of the rear housing in large black ink numbers. For example 185418 = 185 would mean Motorola (MFGR) then 4 would indicate year (3 for 1973, 4 for 1974, etc) and 18 (week of the year)". (Doesn't seem to work for me.)

Somewhere I found this: "Universal Atomic 4, post 1967: 12 volt DC, 35 amp Motorola marine alternator, transistorized alternator-mounted voltage regulator, 12 volt DC solenoid equipped starter (optional 50 amp Motorola marine alternator was available at extra cost)".

Another page said this about the 35 amp Motorola, but I cannot verify that it relates specifically to the ones used on A4s:
"Orange - Output.
Green - F Field terminal to Regulator.
Black - Regulator to Ground
Yellow - Excitor: Coil positive to Regulator."

Another page said "The 1965 Motorola regulators used only 3 wires - Black, Green and Orange. In 1966 an additional wire was added - the yellow ignition feed or "exciter". This "excites" the system. It comes from the coil feed on the starter solenoid. Since the regulator does not ground through its case, but through the alternator, it's a good idea to make sure the alternator is firmly installed and grounded to the engine - normally the brackets will do a good job." (This also does not seem to fit our alternator, which has a black ground wire to the regulator.)
---

[lat 64]

Alternate shop

Tenders,
My first belly laugh of the day, "Bronx Alternator", thanks.

I just got my alt. and starter back yesterday. Even though the starter was "working" He said some of the windings were bad and he put a new solenoid on it. Both got the new bearings, brushes, cleanup, check out and marine paint job. The bill for both was $240.00.

Some information I think one could use:
My guy said the same alternator was used on John Deere and other equipment(see, I told you tractor shop).

The plate that holds the positive terminal post has a diode pressed in it that is for back-feed and over-current protection. Mine has two. This is not one of the rectifying diodes—they are inside. If this diode(s) fails or gets burn up doing it's job, then you can move your positive wire to one of the posts that hold the plate, and you can get voltage again. Only one post is positive, the other is grounded. You can see which is positive. Look closely, it will be bushed out and insulated so it won't touch the plate.
I'm going to test this with a volt meter when I get up and running. This is a good thing to know, like say if you are out in Picnic Cove and you don't get any charging. It might save the day.
I stole Rigs' photo to show which I mean.

A word of caution when picking up your stuff from one of these shops. They like you now, so they will talk till dinner. Allow extra time for this.

Russ

[roadnsky]

ALT Shops

Hey Lat...
You forgot the part about bringing a small ice chest with cans of domestic beer with you when you pick up.

[sastanley]

different areas mean different beers!

Down here in Southern Maryland, those beers are 10 oz. Budweisers.

Except when you take your stuff to the local Mennonites..they don't drink, but their repaired starters & alternators usually outlast the engine.

This is an excellent thread. Thank you, I am printing it out now and adding to my engine folder.

[CalebD]

We fried the alternator diodes on my friends boat which I took to a rebuild shop in Annapolis. It was not cheap at $250 but the rebuilt unit was unrecognizable and looked like new. Lesson learned: do not connect the batteries in reverse pin order.
I can't remember the name of the place but it was as described above, in a desolate industrial part of the town. I think it was between Rt. 665 and 450 and the place was likely near the intersection of Legion and George Aves.
It was not cheap but they did do a pretty amazing job cleaning up the old alternator and replaced the burned out diodes and it is still working two years later.
Good luck.