Ok so my 10AE has an FD alt but on my microtech I normally only see 13.7-13.8v cold and around 13.3 hot. I was hoping to get it up to around 14.5 cold so it would stay up over 13.9 hot.

So I made a diode pack to provide ~ 0.6V drop across the alternator sense wire. I did ground out the voltage sense wire for a split second (wired back to my additional fuse block for all my aftermarket stuff). But that was the only weirdness.

Fired it up and the microtech was reporting 14.6 v. PERFECT. well not quite.

I immediately noticed all the warning lights stayed on. Well the brake light turns on and off but over temp, add coolant, oil..etc all light up. Everything else works fine. Turn signals, horn, engine...etc and no blown fuses.

I pulled out my diode pack, restarted the car and the alternator stayed up at the 14.6 v. Sounds like the regulator was not happy about outputting higher voltage and I'm guessing that a failed alternator turns the lights on.

Does that sound about right?

 

Correct.

 

So I checked the L/S plug on the alternator and low and behold I did not have B+ going to the sense wire. Checking backwards I saw my weather pack (2 prong with a rubber plug on 1 side) was backwards to the alternator. Thus I was not getting power and the apparent fail safe is max output + all warning lights on. max output ~14.7V at idle (measured at microtech dash) and ~15.1 at the alternator.

I fixed the weather pack and it went back to 13.65V idle and all warning lights working normally.

Put my diode pack inline and it jumped to 14.4V idle and all warning lights off. I expect ~14V hot.

SUCCESS! And thank GOD because I'm supposed to have the 7 at a booth at the dream cruise here in Detroit this weekend.

I also noted, I have about a .3-.4V drop from alternator through to my aftermarket fuse block. I think that is alright considering I go through a circuit breaker. I'll double check the voltage at the battery to make sure I'm not providing it too much. I doubt I am as my charger will sometimes provide it 15.2 for a short period of time.

So in conclusion I feel this is a worth-while mod for people that have non-oem charging path that induces voltage drops along the way. Again mine, alternator to batt (pass bin), batt to circuit breaker, to aftermarket fuse block, OE fuse block and starter.

 

Question : Why don't you just get a new FD Alternator and call it a day? don't tell me you can't afford that 100 bux.

 

well, as far as I can tell the alternator was working fine within it's OEM limits. I've also had it checked by a few auto-part stores. However, with the super extending charging system and various terminals along the way I developed a voltage drop that I could not solve with large gauge wiring. I needed a way to boost the voltage to cover that drop. Tricking the sense wire gives me that boost.

I wired it up with weather packs so that if the diode pack ever takes a poo I can hook it back up just like it was before.

 

Interesting concept.

How bout some details on the diode pack so I can play with this?

Thanks!

 

You can get a pack of IN4003's from Radio Shack.

200V, 400V...etc doesn't matter.

Wire them up in parallel to get double the amp rating.

Silver stripe goes toward the alternator. More in series should increase the voltage drop.

If I were to do it again I would look for some 6amp diodes so you can wire just a single in line

 

On a stk series four car the Alt Relay in the CPU causes the warning lights to all come on. This happens when the negative side of the Alt relay sees gnd from the alternator on the white/black wire.

Just saying...I've no idea why all your warning lights came on fully bright with the alt putting out what you said it was putting out.