I upgraded to a FD alternator and now I notice that when I start the car it sits at 10v and slowly goes down until either it dies from the battery going dead or until I bring it above 2500RPM. Once I bring it up it will sit at 14v until I bring it back down to idle, about 800 RPM to which it then drops to 11v-12v. I thought the regulator was bad so I bought a new alternator from Autozone only to find it doing the same thing. Anyone had this problem before? I hate revving a cold engine to 2500 after it just started

I know this isn't technically the section of the Club for this sort of question but this is were I spend most of my time when I'm on RX7Club so bare with me.

 

the alt (both) may be bad. did you wire up the plug correctly? even if your fc is S5, i think the plug is different. i'm not sure though.

I've had 2 bad, brand new alternators before... it sucks.

 

Did you check the alternator trigger wire?

 

Run a wire from the post(OUTPUT) to the top prong of the plug on the back. The plug is not needed

 

Are you talking about one of the two wires for the plug? If so, then yes I checked it. I wired it according to the diagrams I found on here.

Wouldn't that cause problems? Since the reading would be coming off the Alt. itself and not the battery? It should see battery voltage so that it will turn on?off as needed. I don't want it constantly running, Did that with a S4 Alt. and my car sat at 14v all the time for 2 days and then poof, bye bye S4 alt.

Basically it's wired like this..... "Output" goes to the fuse box and I swapped a FD connector onto a one wire harness that comes directly off the battery. The other wire in the 2 wire connector isn't used because it's for the voltage gauge. Here how I wired it, I'm thinking Bucky might be right.

https://www.rx7club.com/forum/attach...1&d=1250350612

 

go ford tempo. its plug and play. no wires to be altered. just can't remember which year it was

 

I have the same issue.

My FD alt doesn't produce electricity at start up unless I rev the engine to like 3k. Then it springs to life and starts charging at 14v.

I just let the car half idle until oil pressure builds before I give it a quick rev.

I assume it's a dirty contact somewhere on the reference and takes a bit of voltage to jump the dirty contact.

My setup does not include the stock 2 wire plug going to the EFI harness/idiot lights. I run the reference wire to the 80amp main fuse(car side not battery side! Ask me how I learned that....)