morgaan

Hi there,

A few months back I was driving at night and my power started to drop to 8~ volts at the cigarette lighter. I thought this was a result of a bad alternator so I just decided to upgrade to an FD3S alternator with a Dual V-Belt Pulley.

Since then, I've had this odd issue where the car will have anywhere between 9 ~and 11~ +- at the cigarette lighter. Once the car is revved to 4k RPM, the electronics suddenly boost to around a solid 14 volts at the cigarette lighter. This happens no matter if the car is hot or cold. If the car turns off after being revved and warmed up, it will still start with the original range of 9~ to 11~ +-. Some have recommended maybe an issue with the battery but the battery is new and I even trickle charged it to make sure.

Does this sound like a bad ground? Or maybe a relay in the alternator is faulty?

Please let me know! thanks

WondrousBread

Does this same thing happen if you observe the voltage guage on the dash? Or if you check with your multimeter across the battery terminals while having a friend rev the car a bit?

It could be the wiring to the cigarette lighter that is causing you to measure a problem where there is none. It also could be bad grounds, Aaron Cake has a write-up about checking and fixing grounds on his website Aaron's Homepage in the Rx7 section.

Typically with that sort of voltage variation you'd see the lights dimming and getting brighter, or other symptoms.

j9fd3s

iTrader: (3)

the cigarette lighters are not the most reliable thing in the world...

morgaan

Mmm I don't have a voltage gauge on the dash. It's a 1986 turbo I had imported. Once the car is revved past 4k from when it's first started, the problem is fixed and the car holds a solid 12-14 volts.

I doubt it's the wiring to the cigarette lighter as like you said, the lights get brighter, the ac blows harder, etc. once the car is revved past that 4k mark. It's almost as if once it's revved to 4k, a relay flips and the car recognizes to give itself more power from then on.... until it's turned off and restarted.

I agree with you. It's more so just to give me an idea of what's going on. Like I said above, there are other noticeable changes in power throughout the car like the ac blowing harder, lights getting brighter, etc.

Rx7 fc

Since you've changed alternators this is quite odd. Some older cars had separate voltage regulators, I think ours are built into the alternator though. I know my weak battery (it's new) and weak alternator (stock 60amp) aren't a great match and cause the voltages to sag frequently as it's cold here. Either I need to upgrade the alternator, battery or both because my lights visably dim with brakes. This sounds like your issue too, and likely your battery is a little weak.

Aidanverse

iTrader: (1)

i have an 87 coupe with an S5 alternator on it, and i have the exact same thing happening as well.
I have a volt meter attached to my oil pressure gauge, as well as my volt meter on the dash. On start up, it would hover about 10v according to the gauge.
I could stab the gas and get it to rev to 4K, and its like the recharge factor gets turned on.

I could replicate this over and over and over, and i couldnt figure out why it was doing that.
I am very new to the FC world, but my thought is that on first start up when the revs jump that there might be some sort of trigger/trip that will have the alternator charge the system.

morgaan

Yeah agreed. I generally always have the ac running so I understand the load especially coupled with a light stereo system and headlamps but still. The S6 alternator itself could be the problem. It's new (reman from Advance Auto) but maybe the relay inside is bad? I decided to connect the power cable directly to the battery and it seemed to help the issue a little but it's still around 12 at idle without ac and 10.5 with ac. Then around 14~ without ac and 12.5 ~ with ac once it's clicks passed that 4k mark.

Hmm I'm actually surprised someone else had this issue. That's my exact problem though too. I'm pretty new to FCs as well. Even though mines an import with an S6 alternator, the issue is the same. Still struggling to figure out what it could be.

dannobre

Did you rewire the alternator? They have different circuits. The FD alternator will self excite at a certain rpm and that might be what you have going on. Is the Alt light on?

morgaan

Yeah I have the original black wire that goes to the ECU connected to the bottom male in the socket and a new sense wire that goes directly to the positive terminal of the battery with a small in line fuse.

I had the power wire going to the back of the fuse box but it seemed to not like it back there so when I moved it direct to battery (hopefully that’s okay) it seemed to have a couple more volts.

I didn’t know that about the FD alternator self exciting. That’s normal?? Alt light isn’t on.

morgaan

Utilized the lifetime warranty and replaced the alternator once again today because I thought maybe a relay in the alternator was faulty. Car still experiences the same problem. The only thing I can think of now is that maybe the alternator is wired wrong? Or my battery is going out? It seems as though before the car is revved to 4k rpm it does not charge the battery.

B terminal direct to battery positive
S terminal sense wire direct to battery positive with 15a inline fuse
L terminal stock wire to dash

Am I missing something here? The only thing I didn't do was run the B terminal battery charging wire to a fused circuit because I couldn't find any good information on that online. Any help would seriously be greatly appreciated.

morgaan

Okay so last night the battery wouldn't charge unless I was moving. At idle it would slowly wind down to 8.8 volts at the cigarette lighter and eventually just turn off.

I went ahead and replaced the sense wire and cleaned the W/B connector. I also cleaned the battery ground.

mr_vaughn

iTrader: (1)

How has the past week been?

morgaan

Better! I replaced the sense wire and cleaned up the main battery ground and now the car is actually holding voltage. About 11.2~ at the cigarette lighter at 800 rpm idle (with e-fan) and 13.5 or so when moving. Battery reads 12.5~ volts when the cars off and 13.25~ when on and getting fed by the alternator. I think my original problem was a bad internal relay in the alternator and after replacing that, my continued problem was just bad grounds. Seems to be all fixed now.