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Alternator terminals and pulley size

hcccs

hcccs

Well Known Member
1. I have a Mitsubishi alternator with markings 23700KA150 and A7T304. I think it is a 45A unit. The terminals are BAT, IG and L. BAT goes to the battery but how do I connect the other two?



2. When I bought the alternator from an auto mechanic he said that it gives its max current at around 4500 rpm and spinning it faster doesn't increase the output. I decided to put on a 4.3" pulley. The belt groove on the flywheel is 9.5" and that gives a ratio of 2.2. 2350 cruise RPMs times 2.2 gives an alternator RPM of 5170 which I think should be enough. Most alternators I see have smaller pulleys but do they give higher output?

 
Hans,
Most alternators will produce maximum rated output at about 2500 to 3000 RPM. I think you have a typo [typographical error] regarding your pulley's belt width. You stated that it's 9.5" [inches] wide. I think you mean 9.5mm. 9.5mm is the equivalent to 3/8".
FYI, the Ign terminal goes to the output wire of an external voltage regulator [if it's externally regulated, which I doubt]. For internal regulation, that terminal gets connected to your master switch The L terminal goes to a warning lamp on the instrument panel. From the numbers you provided, it appears to be off of a 1984 to 1989 Subaru Justy. However, my AllData info conflicts with the results of the Google search I did on the numbers you gave.
Here is where I got the info on the web. See

http://www.woodauto.com/zoomImg.aspx?Ref=ALT32048

Best to ask the mechanic you got it from what it came off of.

FYI, on most Asian alternators, the warning lamp MUST be wired correctly for the alternator to work properly. Your pulley looks like it's of a good size to prevent the bearings from overheating.

Charlie
PS Why use a Mitsubishi alternator off of an oddball vehicle?
First off, the internal fans will be spinning the wrong way. Not a deal breaker, but it will reduce the cooling of the alternator.
Second, my buddies at the local Mitsubishi dealer refer to those cars as "Japanese Jaguars" because of all the electrical and electronics problems they have. That alternator may work fine. I'm just saying that Mitsubishi's reputation for quality electrical parts is not the best.
Third, good luck finding a replacement alternator, if you ever have to find one while away from home. Parts stores don't stock parts for vehicles which did not sell well.
A ND alternator off of a 1981 Honda Civic or 1985-89 Chevy Geo will spin the right direction, last a long time and be easy to find at any auto parts store [Hondas are very popular vehicles] FYI, you can find a 4" aluminum pulley for any small ND alternator [they all have 15mm shafts] at any "hot rod" or high performance car supply shop. Lester # 14131 is an externally regulated, 45 amp unit. Lester # 14684 is an internally regulated, 55 amp unit. Both have fans which spin in the correct direction for use with a Lycoming engine.
 
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Alternator

Yes Jim, the ring gear pulley is what I meant.
Charlie, I think I'll get a Honda Civic or CRV alternator. What year alternator should I be looking at?
 
Lots of choices

hcccs said:
Yes Jim, the ring gear pulley is what I meant.
Charlie, I think I'll get a Honda Civic or CRV alternator. What year alternator should I be looking at?
Click to expand...

That depends on what you want. For an alternator that was originally designed for an external voltage regulator, you want something between 1981 and 1983. The "small" ND alternators generally are rated at or below 60 amps. The larger alternators are in the 60 to 90 amp range. 1984 to around 2000 use an internal voltage regulator and a round plug for the power into the alternator [3 wires] The newer alternators have an oval plug and are also internally regulated. If you would prefer a later alternator, but want external regulation, that can be done with the larger alternators [60 to 90 amps]
Later model Dodge trucks used ND "large style" alternators. However, Chrysler wanted the ECM [Engine Control Module aka computer] to control the alternator. To allow this, ND substituted a terminal block [method to replace the internal regulator with an external voltage regulator (in their case the ECM)]. This modification also requires a different "brush pack" [brushes and holder] as well as the terminal block. These two parts cost under $25 and are easily changed without disassembling the alternator. The change requires removing the sheet metal rear cover for access. The internal alternator and original brush pack can be removed with only the removal of 4 more screws [about 15 minutes work]
I can supply photos of how to do this, if interested. I did not "invent" this modification. That credit goes to Wheeler North. I suspect that this mod would also work on the smaller [30 to 60 amp] ND alternators. I can not confirm that it will, because I don't have a small unit to test it on.
To obtain the correct conversion parts, ask for the terminal block and brush back for a 1995 Dodge 1/2 ton full size van, with the 3.9 V6. Dodge used this set up on many more trucks. I know for a fact, that using that designation, you will get the correct parts.
To get long life from the alternator, you want to keep your expected maximum power demand [in amps] below 60% of the alternator's rating. The big problem with the "small" ND alternators, is that the original design was intended for 30 to 40 amps. The 45 to 60 amp rated units, actually will over stress the diodes in the alternator, if you try to get them to produce "rated" power for more than 5 or 10 minutes. The small size of the units, limits the physical size of the diodes. This limits how much "real world" power the unit can produce.
Charlie
When using a "small" alternator [ND or other] never jump start an airplane with a dead battery, start the engine and go charging off into the wild blue yonder. This is a recipe for a ruined alternator. If the battery is dead, allow it to charge for 30 minutes before cranking the engine. This will ensure that you do not ask the alternator to produce more power than it's diodes can tolerate for more than a few minutes.
 
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Honda Civic alternator

chaskuss said:
FYI, on most Asian alternators, the warning lamp MUST be wired correctly for the alternator to work properly.
Click to expand...

Charlie,
I took your advice an got a Honda Civic -87 alternator. There is a Mitsubishi logo cast into the casing but it should fit a Honda Civic.


altview.jpg


alttext.jpg


In a paper from Vans they say not to use the 'S' and 'L' terminals. I found out that the 'S' terminal is sensing battery voltage. What could it be used for? The 'L' terminal grounds the warning lamp. You said that the lamp had to wired correctly for the alternator to work properly. If you ground a little 12V lamp here, what could possibly go wrong?
 
hcccs said:
Charlie,
I took your advice an got a Honda Civic -87 alternator. There is a Mitsubishi logo cast into the casing but it should fit a Honda Civic.

images snipped

In a paper from Vans they say not to use the 'S' and 'L' terminals. I found out that the 'S' terminal is sensing battery voltage. What could it be used for? The 'L' terminal grounds the warning lamp. You said that the lamp had to wired correctly for the alternator to work properly. If you ground a little 12V lamp here, what could possibly go wrong?
Click to expand...

Hans,
I've never seen a Mitsubishi alternator in a 1987 Civic. That said, manufacturers often source parts from multiple vendors. Reasons for this can be to protect themselves from a strike at a vendor or because a single vendor can not supply the volume they need.
I've checked both AllData and Mitchell On Demand regarding wiring for the 87 alternator. [They make no mention of a Mitsubishi alternator. Only the ND unit is mentioned. That said, there are several variants of the 87 Civic, including a fuel injected model. Perhaps the Mitsu unit was used on a variant?]
You can ignore both the S & L terminals, if you desire. If you would like to install a "charging system warning" lamp on your instrument panel, you can use the L terminal. FYI, the wire coming from this terminal goes to a fused POWER wire, not to ground.
The idea is that so long as the alternator is working, you have 12 to 14 volts positive, at both ends of the wire. With no ground, the lamp stays out. An alternator failure will provide the lamp with a ground at the L terminal. The light will then go on, warning you that the alternator has failed. Make sure that you place a fuse between the power source [master switch] and the lamp on the instrument panel.
Charlie
 
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