hammmy

Ok, I've read both threads listed in the 1st Gen RX-7 FAQ. I've read the threads they reference from other 2nd Gen forums. I think I've managed to understand how the S5 alternator is supposed to be wired into a 1980 SA chassis, although the threads are very confused--the "Economical Alternator Upgrade" thread appears to be flat-out wrong: https://www.rx7club.com/showthread.p...hreadid=239526.

On both the 1980 SA and 1989 S5 wiring diagrams, there are 3 circuits connecting to the alternator. For the SA, these are the main battery lead (B-terminal to battery), the choke-and-check relay (L-terminal WB wire on 1980), and the ignition switch (R-terminal BW wire on 1980). For the S5, these are the main battery lead (B-terminal to battery), the choke-and-check relay (L-terminal), and the always-on battery voltage reference (S-terminal).

From what I've read, some people have wired the L and R-terminal leads from the SA chassis directly into the L and S-terminal leads of the S5 alternator. This apparently leads to battery discharge, due to the S5 alternator's internal regulator needing a constant-on voltage reference between the L and S-terminals. In a S5 chassis, this would be provided because the S-terminal is electrically the same as the B-terminal (+12V battery). In the SA chassis, this is not provided when the ignition is off (see R-terminal circuit diagram pic), leading to a slow discharge of the battery through the choke-and-check relay circuit whenever the ignition is off.

After studying this last night, and confirming with certain statements made in the "2nd gen alt in 1st gen?" thread (https://www.rx7club.com/1st-generation-specific-1979-1985-18/2nd-gen-alt-1st-gen-373411/), I think I see the correct way to wire the S5 alternator into the SA chassis. The B-terminal lead is the same, although the loop connector to the S5 alternator's B-terminal stud is a different size. The S-terminal on the S5 alternator is connected to constant battery voltage: most easily accomplished by using a jumper wire from the S5 alternator B-terminal to the S-terminal (see S5 80-amp Alternator pic) The L-terminal lead (WB wire on 1980 SA chassis) is connected to the L-terminal of the S5 alternator. The R-terminal lead from the 1980 SA chassis is not used, and is capped.

Does this all sound correct? Please answer this thread only if you know absolutely. We do not need yet another thread saying to install n diodes and relays in place of wiring correctly. If this is correct, there should be some thought put in to removing the "Economical Alternator Upgrade" thread from the 1st Gen FAQ Page.

Thanks,

gsl-se addict

iTrader: (3)

Yes, the correct way to do it is the way in the 2nd gen alt in first gen thread. The way in the economical alt. upgrade thread will cause discharge with the car off. This is fine if you use the car daily, but will kill your battery within a couple days. Mar3 did a great job on the write up/ drawing for that thread, but unfortunately, the wiring is incorrect. However, to give Mar3 credit, this way of wiring was published everywhere at the time. Everyone was hooking up their alts incorrectly and adding diodes/relays to try to correct the problem. Hope this helps with clarification. If you have any questions, feel free to pm me as I have done this swap in my GSL-SE.

Kent

EDIT: BTW, that is exactly how I wired my alt in the first pic. I also used the female spade connectors, as I didn't have an S5 alt plug available. It sounds like you have everything under control.

hammmy

Good, I was hoping you'd respond. It was your comments that cleared up what to do with the R-terminal lead for me.

I'm going to go install the alternator now. Wish me luck.

-dave

gsl-se addict

iTrader: (3)

Good Luck!

Hope it works out for you. I only found the correct way to do it after reading around a bunch before I installed mine. At least one of the guys on teamfc3s screwed up their FD alt by wiring it wrong. First he installed it the way shown in the economical alt upgrade thread. He had battery drain, so he was told on teamfc3s to reverse the connections. This ended up messing up his alt. I am very happy with the results from the swap.

Kent

Rex4Life

Last night I installed an FD (same as S5) alternator in my SE. The wiring is exactly like you said. The wire I capped off was a Black/White.

And I ran a new red wire from the 2nd gen fuse block to the alternator S terminal. I thought about using the jumper like you did but felt there was surely a good reason it was not wired that way to begin with.

Works great!

hammmy

Regarding the jumper wire, the person on the board I bought the S5 alt from sent it with the jumper attached--although on the L-terminal, which had me crossing my fingers today that the alt wasn't dead. I probably would have made one anyways, instead of running a fresh battery line. I'll have to think about why the electrical engineers ran a separate harness line; maybe I'm missing something, as Rex4 suggests.

Hopefully there'll be no battery discharge in the morning. If I have some free time, I'll put an ammeter in to see if there's any significant current pull.

Thanks for your input,

-dave

hammmy

Just noticed that I didn't follow up on this thread. I've seen no discharge of the battery. I left the car sitting for a week and a half, and it fired right up as usual.

-dave

mar3

iTrader: (8)

That is exactly what I was told would be the result of getting the wiring wrong. Strangely, the 1980 Rx-7 I had never exhibited the battery drain after the swap that I'm currently seeing in the '83 and the '84....however, I will go the relay route to assure my alarm doesn't see any current fluctuations in the electrical system and think it's being invaded...



ps. Disregard the avatar, that's for the DoO dopes, myself included...

gsl-se addict

iTrader: (3)

hammmy: Glad to see that you got it working okay. It is always nice when people follow up on their thread. There are so many threads on here that go incomplete and that doesn't benefit people in the future.

Mario: Why don't you just connect the S terminal to the battery output terminal? I would think this would be better and easier than installing a relay. I wonder why the '80 didn't experience battery dran. Maybe you drove it enough to where you just didn't notice it. Most of the wiring issues come from people using both of the L/R wires on the L/S terminals with the wires then crossed (because they get discharge the other way).

Kent

mar3

iTrader: (8)

I'll give it a shot and see what my alarm thinks of it...

H4Inf

Just wondering what symptoms would occur if you just plugged the connectors on backwards or something? I got an alternator which was apparently from a later model RX7, and have put it in my 1982... I just plugged in the plastic plug and it went in fine, and the car seems to go fine except when the headlights are on there are some weird elec. problems.

gsl-se addict

iTrader: (3)

As long as it was the same style plug as the '82 had, there should be no problems. The style of alts stayed the same though '88 on the 7s (just max current output changed). You only have to worry about wiring issues if the alt is '89 or later. The style of regulator changed in that year, so that is why the wiring change is needed. The plug on these are completly different than the early style plugs (hammmy's post shows what the '89+ style plug looks like).

Your electrical problems may be coming from another source. Check your grounds, battery terminals, battery cables, etc.

hammmy

For headlight weirdness, I'd re-seat the fusible links.

RotaryRevn

do you have to change your pullies if using and fd alternator?

gsl-se addict

iTrader: (3)

Yes, you need a different pulley to use the FD alts. You can get an FD alt from silverrotor here on the forum that has the pulley converted, if he is still making them. They come with either a single or dual pulley setup the will work in SAs, FBs, and FCs.

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/fd-alternator-kits-fitted-fcs-now-sell%2Alast-date-purchase-sept-1-%2A-397719/