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Index > @ the Pickup Bed (General Topics) > Thread: how to upgrade to 2nd gen alternator?
Thread: how to upgrade to 2nd gen alternator?
brad


Rotorhead
Posts: 1672
posted January 23, 2003 09:54 PM

how to upgrade to 2nd gen alternator?

The 89-92 turbo ][ alternator puts out ~90amps if I remember right, and it has a built in regulator. I got one on the 1st gen running fine. REPU has a 40 amp alternator with an external regulator.

Who has put a 2nd gen alternator on their REPU? And how to I get rid of the external regulator?

The + output wire from alt to fusebox to battery is 6 gauge which can handle the voltage fine. Only other concern is the little fuse behind seat fusing the alt + wire and the battery is rated at 50 amps. Odd little long wafer looking fuse. Anyone know if these can be had for 100amps? Otherwise I'll need to splice in one.

Thanks,
____________
-brad-
74 REPU Lawn Green
81 Rx-7 racecar. 12a J-
Bridge

       
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Jeff20B


Moderator
Posts: 661
posted January 24, 2003 11:09 AM

I installed a 1st gen 50 amp alt a few years ago in my REPU. Then just recently I installed a 2nd gen 55 amp alt. I went back to the 50 amp a couple months ago so the smaller 55 amp alt could be used in a rotary project car.

There is a T shaped connector on the back of the alts from around '81 to '88. The later higher amp units had a different style, but they're still easy to hook up if you know which wire goes where (I don't know off the top of my head). There is a diagram floating around the net which shows you the differences. Maybe somebody else will know. Anyway, I was lucky that both my alts are so close to 50 amps that I didn't need to mess with the fuse (It's just a strip of lead of appropriate thickness). I don't plan on running aircraft landing lights or a high power amp anytime soon, so I think I'll be ok.

Here is a pic of where my voltage regulator used to be. I jumpered the wires that used to go to the reg (seen in the green circle). This allowed me to keep using the stock wires and all I had to do was splice in a T shaped connector where the 4 way one used to be. The T shaped connector consists of one wire which goes to the 'G' dash light. The other goes to the key (on) switch. The fat battery wire remains unchanged.

By the way, if you're curious, the thing sitting where the voltage reg used to be is my ignitor heat sink.
____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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Jeff20B


Moderator
Posts: 661
posted January 24, 2003 11:12 AM

Here's a pic of the backside of my 50 amp alt. It may be a little hard to see, but it shows the T shaped connector and the battery wire.

____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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Klaus43


Rotorhead
Posts: 1259
posted January 25, 2003 12:29 PM

Hey, what's that funky looking fan setup you've got there?

       
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Jeff20B


Moderator
Posts: 661
posted January 27, 2003 10:28 AM

It's just a 16 inch electric fan mounted to the stock fan shroud so air could go through the oil cooler as well. I've since gone back to a clutch fan. It eats a lot of engine power though.
____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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brad


Rotorhead
Posts: 1672
posted January 27, 2003 10:40 AM

did the electric fan work Jeff? Why'd u switch back?

I want to go electric fan and the best option is a Black Magic 150 fan that moves 2800cfm. Lots of 1st genners use this fan. About $250 with adjustable thermostat.


____________
-brad-
74 REPU Lawn Green
81 Rx-7 racecar. 12a J-
Bridge

       
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Jeff20B


Moderator
Posts: 661
posted January 28, 2003 11:07 PM

Yeah it worked, but I wanted to experiment a little. I think I've figured out what I needed to know and may go back to the e fan someday. Actually, it seemed a little underpowered compared to the clutch fan, which seems a little too powerful. The engine takes longer to warm up with the clutch fan, which isn't a very good thing in the winter. But the engine didn't overheat in the summer with the e fan either.
____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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Uncle-Jim


Revvin Up
Posts: 64
posted January 29, 2003 11:15 AM

Alt. Upgrade

I did this last year on my Rx-2. Last night I got out my wiring diagram to refresh my memory. I used an alternator from a first gen Rx-7. This has a built in solid state regulator, and is a bit smaller than the equivalent Alt's used earlier by Mazda. My recollection is that the 2nd Gen alt. is very similiar.

Here's the things to watch for:

All alts. need battery voltage supplied to excite the stator windings and provide reference for the volt reg. Where the older units had a four pin connector to the ext. reg., these newer ones have a two pin connx. (plus the stud for the hi-amp connx).

The lower pin (R) has to be supplied with voltage from the battery, switched thru the ign. switch so that 12v are present when the ign. sw is either On or start. This connx supplies the ref. and excite power. This wire is usually black and was in the four pin connx.

The upper pin (L) is wired to the Alt. lamp on the dashboard. This lights up the idiot light if the Alt. voltage is below the battery
volts. It serves as a warning that the alt. has either stoppped or has failed. Like just before you start the engine. This was also in the four pin connx - and I think it was yellow/brown (?)

I didn't use this in my car, since I have the ammeter on the dash,and didn't have the idiot light. Don't quote me on the color of that indicator, although Mazda used yellow as the code for any indications whether meters or lights. (Black is the code for 12v present whenever the ignition is on).

Finally, you can reconnect the heavy white/red wire to the stud on the back of the alt. This supplies the high-current output to the battery, fuse terminal, and thence, to all other circuts.Check the engine harness connx, and inter-chassis connx for this heavy wire. This was a weak point in Rx-2, 3's, early REPU's and frequently you would find the spade pins and plastic around them overheated. You could solder in another connx in parallel, to divide the current load, or what I did, re-wire all the white/red with heavier cable and not use the chassis connx at all. (I got a good deal on a bunch of that red 8ga. audio amp wire, and used that).

Sorry for the long post, but I know of several Rx-2's that went up in flames when someone (I'm one of them) overloaded the stock wiring, or shorted the ammeter behind the dash. (I was able to save my car.)

I'll try to make up some graphic of my wiring and post here, or I'd be happy send along any drawings at your request.
Jim

Btw, I have a 16" eFan in my Repu, and have had no problems keeping the engine cool. The Fan is mounted across the lower part of the radiator, and oil cooler. I'm using a thermostat sensor mounted in the fins of the rad.

____________
Uncle Jim
72 Rx-2 Show Car; '77 REPU (250K & goin' strong) 2 - '76 Cosmo's

       
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