Kentetsu

Had an issue ever since pulling the car out of storage. On a daily basis I would blow the center fusible link (which is actually a 30 amp inline fuse). I couldn't find any wiring issues, so I tried a 40 amp fuse even though I'd been running a 30 amp for a couple of years without issue.

That lasted for a couple of days until both headlights exploded internally on the way home from work at 3am. It seemed that I was getting voltage spikes, so I took the alt in to Autozone for testing and they told me it was fine.

I figured maybe it was an intermittent issue with the voltage regulator, so I went ahead and swapped it out with a Hitachi alt I had laying around. All wiring hookups were layed out the same as stock, but I'm not sure if the connections still serve the same purpose as the Mitsubishi alternator it was replacing. Anyway, I tried it out but it wouldn't charge (volt meter stayed at 12).

Now, I know that the alternator needs a 12 volt signal in order to start charging, so I ran a line from my coil+ to one of the plug connections on the alt and right away it started charging. Volt meter went right up to 14 just like it should. However, on the way in to work tonight, it would sometimes jump up to just under 16 volts. The 30 amp fuse held up though.

Questions:

1. On the stock wiring, at the plug that goes into the back of the alt, one of the tabs should be showing 12 volts, right? It doesn't. I'd like to know where to start looking to troubleshoot that.

2. Voltage rising to 16 volts. Could this simply be due to a higher amp alternator? I think this one is like 100 or 130 amp, but not sure. It is a lot larger than the stock one though.

3. With the engine running, I pulled the center fusible link to see if the system was charging on its own. The motor kept running, but my efans went from running good to running like a bat out of hell. Why would that be? Do I have some major drain on the electrical system that was bypassed when I pulled that link out?

Any information or guidance on these issues would be greatly appreciated. I know just enough about alternators to get myself into trouble.

waysrx7

Well, I can answer your first question. The top connector should show battery voltage only when the ignition is on. It is a BW wire that goes to the 20A fuse under the steering wheel, then to the ignition switch, check if it is fried and if it is connecting to the alt properly/making good contact. If this wire or the big fatty WR wire on the back of the alt aren't contacting well and give variable reistance, it could cause voltage spikes by causing the alt to work harder than it needs to to overcome this resistance. This also sort of answers question 2.
The bottom wire on the connecter doesn't affect how the alt works, it is just used for the waring light and choke and check relay.

themayor500

I had basically the same problem, took me ages to figure it out. In my case it was not the wiring that was the problem, somehow the internals of my alternator had failed and gave me an output voltage of 16v most of the time and would spike to up to 24v. I was unaware that that could even happen, its free to have that tested and all the parts stores, I would make sure that you arnt having problems with the alternator before you pull your hair out with wiring.

Kentetsu

Thanks Waysrx7. Neither connection in the plug shows voltage with the key on, so I'll check that fuse out.

I'll have to find a wiring diagram for the Hitachi alternator though to be sure that the hookups are the same. I'm pretty sure that this alternator was from an Isuzu Trooper, so I'll keep looking.

Kentetsu

Forgot to mention earlier, but this morning on my way home from work the meter stayed pegged at 16 volts. About two seconds after I tried to use the highbeams, one of my brand new headlights blew.

I really hate electrical issues that I don't understand. lol

waysrx7

I doubt its the fuse because it is a major one, it goes to the fuel pump as well as a bunch of dash lights etc. If it was blown you couldn't start your car.

As you can still run your car that BW wire may be damaged between your alt and the fuse which would explain no voltage to it but leave everything else okay.
Check the big mother of a conneter on your passenger side that connects the engine harness to the body, the BW wire that connects to another BW wire that your looking for and check for a fried wire or damage.

For now I would troubleshoot the reason your not getting power to the BW wire because it is a known problem, it's necessary for your alt to work, and you said you already had your alt checked.

I'm assuming this is for the '85 in your sig.

Jeff20B

iTrader: (13)

Perhaps the positive or negative connection to your battery is bad. When the + battery terminal in Percent's car was making intermittent contact, it spiked the alt up to 24V but since it was during the day, the headlights weren't on, so they didn't explode.

gsl-se addict

iTrader: (3)

^ Yep..just about to say check grounds and check the connections at the battery. Also make sure that the alt is getting a good ground through the mounting brackets. If there isn't a good path for the current to flow, you will get a high voltage (and can get spikes).

The voltage spikes sound like a bad regulator, but the problem is there with a different alt too. The 'R' terminal at the back of the alt should be switched 12v..so power should be present when the car is on. The 'L' terminal is for the warning light. I'll have to check the wiring diagrams, but I'm pretty sure that is on the engine fuse.

Kentetsu

Okay, you guys are sparking some thoughts here. Let me see...

1. Ways says that if the fuse blew under the console, my fuel pump wouldn't run. What a coincidence. About 10 minutes after installing this motor my fuel pump failed. Jumpering the relay did not seem to work (couldn't find any power going to it), so I ran another hot wire from the coil+ to the connector at the relay under the dash. That got my fuel pump running.

2. Wouldn't have any dash warning lights. I don't believe I do. There is only one red light that comes on when I turn on the key. Not sure if it was like that before I rigged up the new alternator, wish I could remember.

3. Battery cables are under a year old, and heavy duty. Connections at the battery are cleaned and verified as of two days ago when I installed a new battery (think the old one died due to high voltage but not sure). I will double check my connections down by the starter for both cables when I get a few minutes.

4. I have always ran a 10 gauge line from the alternator bracket to the negative post on the battery. That is in place.

5. I am currently feeding 12 volts to the R terminal from the coil +. L terminal is not connected.

And yeah, this is all dealing with the '85 in my sig (my wife would kill me if I owned more than one).

This is also dealing with a recent motor installation. But understand that my engine bay is pretty much stripped down to bare necessities, so there aren't a whole lot of chances to screw up and get wires crossed.

I really appreciate your thoughts guys...

waysrx7

Let me refresh my brain,
1. the 20A fuse I mentioned is on the left side second from the top in your fuse panel which goes to the alt, fuel pump and emissions system.

2. Dash lights, ops, I was thinking of my SA 20A fuse for a moment when wrote that, your lights shouldn't be affected.

3. If the wire is bad you shouldn't have any emissions stuff working, ie choke, rats nest junk.

I think the short/bad wire would be inbetween your fuel pump relay and the 20A fuse; this is based on the info that your not getting power to either BW wire on your fuel pump relay plug with the ign on. At least it should be for your fuel pump problem.

EDIT: also check to make sure you are getting power TO the 20A fuse.

Kentetsu

Hmm, well the first thing I did when the pump failed was to verify that all of my fuses were good (which they were).

No choke on my car, and no rats.

I'll keep chewing on this and see what I can come up with. Maybe I'll just upgrade and rewire the whole damned system in a way that makes sense to me.

Kentetsu

Problem solved. Conclusion, I am guilty of making assumptions. What an idiot!

1. Assumed that wiring at the starter was good because I had just installed the motor. After all, surely I know how to install the wires at the starter, right? Wrong, found the main power cable loose.

2. When Autozone told me my alternator was fine, I assumed that my gut instincts were more accurate than their test procedures so I replaced the alternator with something I had laying around. Wrong, alternator was fine.

3. The alternator I put in as a replacement had a bad voltage regulator. This threw me off, because with the old alternator in I was also showing voltage spikes, so I figured that the alternator was not the issue. My original alt was spiking due to the bad connection at the starter.

So, I fixed up a bunch of wiring the might have been "questionable" and tightened up the power cable at the starter. Tried it out and still had 16 volts showing. Put the original alternator back in, and now I'm golden.

Thank you all for your replies and input, and also for your patience. This only shows that experience does not make one immune to stupidity.