Battery Drain
 

Hello,

I have a battery drain issue in my girlfriends 91 fc S5, I did a parasitic drain test on the car to see if i could locate the problem. I have found the fuse that is causing the problem which would be the EGI fuse under the hood. I presume this fuse is for the electrical in the engine. When the car is at rest im sitting at 274mA, and with the fuse unplugged im getting 14mA. Anyone got any ideas for me.

Disconnect the wiring to the alternator.

Do a drain with the wiring to the alternator taken off? If it lowers the draw it then what?

then the regulator in the alternator would be the culprit.
You have to start somewhere as that circuit has a lot of stuff on it..like those stupid solenoids.

it seems like there are 2 relays still getting a trigger. I will test the alternator when its a little warmer and not an icy mess. Are there relays under the hood?

How did you come to this conclusion? You could also try unplugging the Main Relay. It has two plugs and the one w/four wires should be unplugged and then check for a continued amperage drain.

Because at first at rest it is resting at 300mA. A standard SPDT relay takes 150mA to power the copper coil or terminals 85/86. just wondering if there are relays under the hood anywhere to check and make sure one isnt staying on.

Main Relay has two relays.

where exactly is this located in the engine bay.

It's behind the driver's side strut tower, near the Clutch Master Cylinder, Trailing Ignition Coil and Brake Master Cylinder. It's about twice the size of a Bosch-type relay, with a metal case and has two connectors with ~3" of wire. IIRC, it's secured to the inner fender with what looks like a self-tapping screw.

The 2-pin connector, named F-32 in the Wiring Diagram, is the coil pins. Wire colors are Black/White and Black. Connector F-33, the Power Pins, is the 4-pin connector, which feeds the ignition coils and almost anything related to the ECU.

To do the test you need to do, unplug F-32 and check the current draw.

Okay I redid the drain test today. I narrows it down to the top terminal kn the back of the alternator. Is this a necessary wire? Its pulling 260mA with the ignition off. I followed the wire and for some reason looks like its going to the top of the tranny but I guess it could have split off somewhere in between.

So, when you unplugged the alternator initially the drain still occured but now it doesn't? And what is top terminal kn? Is this the L terminal (W/B wire) or the S terminal (B/W wire) you are speaking of.

The wire colors aren't correct. Okaythe alternator doesn't have the factory plug do the backside anymore it has to female spade connectors. And bow there is a red wire and a black wire. From the diagram I saw on the forum it looks like the "L" wire.. alright so I started the current draw which initially reads 274mA when that "L" wire is unplugged the draw drops to 13mA. So whatever that wire goes to is causing the drain.

Oh and i figured out it has a s4 alternator.

Oh and my fault it's the "R" terminal

The L terminal runs to the Alternator Warning Light Relay in the CPU. The relay is powered by the Meter fuse. If the Meter fuse is pulled and you still have the draw then the problem likely resides in the alternator.

Where does the r terminal go. I think somewhere at the ignition but what is it used for?

I explained about the wrong terminal, my apologies. The other terminal should run to the 15 amp Engine fuse for an S4 alternator (goes to a different spot for the S5 alternators). The Engine fuse should only have voltage w/key to on so check the wire for voltage w/key to off and if it has no voltage then your problem lies withing the alternator causing a drain. If the S4 alternator is wired improperly then it will eventually cause a diode to burn out and when this occurs the alternator pulls voltage from the battery w/engine off when it should not.

I guess my question is do i need the R terminal or can i just unplug it. Because everything seems to work fine with it unplugged. Still charges and all accessories still work.

If the alternator is not wired up properly you will damage it. Secondly, an S4 alternator is wired differently than an S5. If you pulled the plug off of the back of the alternator then both wires should have voltage w/key to on. Look at wiring diagram for the alternators provided in the FAQ.

hmmm. I checked the diagram but why does the alternator need a wire to the ign? its belt driven, and creates power through 3 stages of rectification. so why does an ign input affect rectification? thats what im trying to figure out.

But thank you for all the help!

On an S4 the B/W wire powers the alternator and the W/B wire excites it. All you would want to know about these alternators is found within the following link.

https://www.rx7club.com/2nd-generati...-819259/page2/

Thank you!

Edit: Okay so i read throught that whole thread. Now the diagram shows the "R" terminal going to the ign, If i cant find that blac/white wire to hook to then can i run it to a switched ign and fuse it? so that when the ign is on the alternator is still exciting?

How does the wire currently behave that's connected to your R terminal? It should have voltage w/key to on/start only. You could wire it that way, but remember, the Engine fuse is powered w/key to on/start as opposed to just key to on.

Well if I use ign 1 it would act as key on and key start. I havent had a chance to teat the wire to see if the alternator is keeping it on or not. But when I traced the wire it looked like it went to the tranny which made no sense