thadrunknmunky

well after reading around in this forum ive learned a couple of things of why my car drains the battery so damn fast (killed my 4th one going for #5 in one month)

first off, i drive an 86 GXL 5spd

-i thought it would be a bad fuse. so me n my dad found out that the 'room' fuse was causing all the draining. as a result all my interior door lights and clock will obviously not work. but as i was driving that same night, my clock was slightly fading on and off.

-then i thought it would be the alternator since my battery meter was only reading 12.1 - 12.2ish... well i removed it and got it tested at kragen and it passed all the tests. so i dont think thats really the problem either.

so now what should i do? could it be the charging system? starter? hope u guys can help me. it's really getting frustrating

thadrunknmunky

err i meant what's else could be wrong with my charging system

brohr01

wiring could be shot, you could have a parasitic drain on the system, you could have a short to ground on the charging circuit, bad grounds. get a multi-meter and check out the resistance on the wiring and for shorts to ground.

Icemark

If your volt meter is reading less than 12.6 volts you are only running on the battery and not the alternator.

With the car running you should be at a minumium of 13.5 volts. If it is not, then you have a bad alternator or bad connections (but probably an alt).

And Auto zone/Kragen/Etc has no clue how to test an alternator. They can only test if the diodes are good or not.

and you say you tested for current draw... how much draw did you have??? what did your digital multi-meter tell you that was/is the draw?

Kenteth

You know mark, I vary rarely see my stock volt meter above 13.

Before the fd alt swap It was between 12 and 13. When I installed the fd alternator, I would occasionaly see above 13, if everythign was off it might go slightly higher...
The fd alternator tried to melt the b-post to the uim. I removed it and sold it to project84 who was going to repair it. Coincidentaly, now that I'm back with my old fc3s.. I still never see much above 13volts. This is running a clutch fan, no stereo, and a 10amp set of foglights...

I've grounded the alternator and added a wire from the bpost directly to the battery. Car runs and charges fine... I've never had to jump start so I know its charging.

coincidentaly, I did do a test when the fd alt was installed. With my multimeter I saw low numbers aswell.

I dunno... car seems to drive fine and starts fine everytime...

WAYNE88N/A

Kenteth- try taking the ground off of the alt, and using the OEM rear rotor housing ground. That's the way the system was designed by the Mazda engineers...Your alt ground, if beefy enough, is fighting with the starter ground. I'm not going into another thesis on these ground wires with you guys...The OEM system works fine, as long as the continuity is there (clean metal-to-metal contact).

Kenteth

they are clean. Interesting you mention that the extra ground could actually be doing a disservice by routing the -es back to the battery instead of directly to the starter.

Either way though, the current will take the path with least resistance, more than likely directly to the starter...

WAYNE88N/A

Yes, like water, current will follow the least resistive path. Also like water, when confronted with two, three, or more similar "resistive" paths, the flow will be "confused", for lack of a better term, and will actually "split". Take multiple ECU grounds for an example, for our sensors. Give it 3 grounds with .1, .2, and .3 ohms of resistance. At the speed of light, the least resistive path will be chosen. Now, being that the mere act of current flowing through a circuit or wire creates its own resistance (known as reactance), the flow will now jump to the .2 ohm resistance circuit, and back & forth, on & on, until the end of time. The real world proof of this happening are the guys who all of a sudden have a shitty running car after they ground the boost sensor wire. Why? Think of it this way- run 2 power wires to a computer, exactly 12v on one, and 12.1 volts on the other. Which will provide the power? The 12.1v, of course, since the potential for current flow is slightly higher. Now what happens when that power is used by the computer? The voltage drops under load, and the 12v power supply input takes over, until it too drops under load. This is exactly what happens with multiple grounds. Some of you guys seem to think the grounds are somehow more important than the power wires, and that by adding more the circuit (or entire car) will somehow work better. If you have a 1/2" water supply pipe, and add a 1" extension onto it, you're still going to get 1/2" worth of water out of it. Same scenario with the grounds. They're just the "other side" of the circuit, and no more or less important than the power wires. If you're going to beef up a circuit by adding a huge ground, you must add a huge power wire too, to get any results as far as voltage drops are concerned...

The alternator was engineered and designed to ground through the mounting hardware, and the voltage regulator & IC circuit were designed with this in mind. You're dealing with very small corrections inputed to the field excitation circuit of the alt, which determines the output generated for a given load & rpm. Kick up the field just .1v, and you're going to see somewhere in the neighborhood of a 1 volt output increase, and the same scenario happens the other way also...

And here I said I wasn't going to write another thesis, lol...

Icemark

To charge a automotive battery, you need at least 1 volt over the voltage of the battery. So since 12 volt automotive batteries are really 12.6 volt batteries (six 2.1 volt cells), to charge them you would need 13.6 volts.

Normal automotive electrical systems run at 14.4 volts. Everything in the car is designed to run at that voltage. An alternator working correctly will put out 14.4 volts regardless of amperage load (until the amperage load exceeds the alternators capability).

So if your car is really running at less than 13.6 volts, you will be down on spark energy, down on injector flow, down on power.

I suspect in your case that either your grounds are very very bad, or your volt meter is not reading correctly (it is common to get corrosion on the screws on the back of the gauge cluster that will increase the inaccuracies of the gauges). So you need to get a digital multi-meter and really read what the voltage is.

The other option is that you mention that you are using a FD alt. If this is the case, you will need to double check the input/output small gauge wiring on the alt. You may have the wires backwards or not connected correctly.

But if it really iis as low as you say, and you have checked those things, then upgrade the grounds, and replace the alternator.

thadrunknmunky

never mind, found out the problem... i just unplugged the plugs to the cabin lights and replaced the alternator. it runs fine now. thanks guys.

tKslVguyen

Hey I have a really similar issue to yours. But when you said you unplugged the plugs to the cabin lights, do you mean the fuses for cabin lights?

I could never get a reading of 14v with my meter from the back of the Alt -> Chassis.

I think in my case I'd have to go look into my ground wires and replace them if needed =x

satch

iTrader: (1)

The Black wire bolted to the side of the alternator is the voltage output and this is the wire you measure the alternator voltage from (engine running) and not the back of the alternator. Also, in your own words explain your problem rather than have folks read through all of the previous crap in this thread.

tKslVguyen

@satch: I am reading voltage from the black wire bolted to the side of the alternator. When the car is idling it's 13.3 volts. If the e-fan (flex-a-lite syclone 16" @ 17amp), my voltage reads 13.1v @ idle. The e-fan is adjusted to a temp that is reasonable to turn on, so it's not on all the time. When the car is in motion and the e-fan is not running I'd get about 13.0-13.4 (never hit 13.5). I hear that the normal voltage when the car is in motion around 2k-3k rpm it should be +14v right?

If I was to turn on my stereo w/ amp to 2 6x9s, my headlights and the cabin fans (no A/C), the voltage would be around 12.5v-13.0v at most. The battery I just received is a brand new D35 Yellow Optima from a friend that helped me trade in my Red Optima 35. New battery is tested and all cells are great.

I'm suspecting the Alternator could be not as good as it should be or this could be normal for the oem 80amp? This alternator is about 1yr old, it's definitely charging but not efficiently apparently.

I'm thinking of going out to get some nice 8gauge wires with insulated ring connectors and change out some old ground cables. Next thing I'm looking towards is upgrading that alternator right?

Well that's whats going through my mind. Anyone have any suggestions at what I should also check and look into?

Thanks ahead fellas, shed your knowledge upon me ^^

satch

iTrader: (1)

Your numbers are a little on the weak side but to be expected with that type of alternator plus very old wiring. Check out the voltage drop section in the link provided and this should give you some insight to your situation

http://www.aa1car.com/library/charging_checks.htm

tKslVguyen

i checked out the link, thats good info to troubleshoot with. I'm going to go with changing out corroded grounds and look into an alternator that japan2la is selling for fc's. Anyone have experience with the alternator that he sells? Or anybody know where i could get my hands on a bolt on fit, high output alternator?

satch

iTrader: (1)

For reference purposes I get 20 millivolts when doing the voltage drop test related to the ground side and 15 millivolts for the positive side. Below is a link to a site that will rebuild your existing alternator to a level that exceeds the 3rd generation and the other advantages are that it is plug and play as opposed to the changes required with installing the 3rd gen's.

http://irperformance.com/

tKslVguyen

Tomorrow I'm going to start changing out old wires with new 8gauge (green) wires I got at my local home improvement store =)

Hopefully this all turns out well before SevenStock13 this weekend =x

tKslVguyen

i had time today to change one of my cables. The cable from the alternator to the fuse box was noticeably corroded. I used about 3 feet of my new 8 gauge stranded wire from home depot. After installtion i started the car and took out the meter to check voltage. The alternator puts out 14v! The battery is showing 13.7 idle. With my efan on it reads 13.5. The only thing left is to get to my ecu grounds, ecu is showing 13.2v. That one corroded was robbing me of about 0.3v, thats alot of resist
ance! I'm so glad its showing progress.


Post up more later when i start chaning out more of those old grounds.