23 replies to this topic

[Durania]

Well put the newly rebuilt alternator on the brat today. Drove it up the road and my voltage is still reading at 9 or 10 and my windshield wipers are barely moving. Every now and then my gauge lights will go out and my tachometer ceases to work. This includes all electrical lights. Does anyone know what could be causing this? Bad ground on the alternator is what I am thinking. The previous owner thought it was bad distributor bushings. What do you all think?

[GeneralDisorder]

Probably bad grounds in general. The Headlight ground is behind the left front speaker.

Check the ground behind the battery on the left fender wall.

Also check the ground on the left side of the intake manifold, and the one from the tranny to the spare tire shelf, and the one on the drivers side strut tower.....

The alternator grounds through the engine block.

Check voltage off the back of the alt and compare that to the voltage at the junction point (fuseable link box). It's normal for the back of the alt to be about .5 - 1.5 volts higher depending on accesories turned on.

GD

[Durania]

Yet again, provide quick and effective advice. I will get up early in the morning and check my grounds. The dude at the alternator shop said that if I had any trouble run it by. I will run the brat by there tomorrow and have him check everything out. Would the bad ground also cause my fuel gauge not to work?

[GeneralDisorder]

Would the bad ground also cause my fuel gauge not to work?

Maybe, but that's often associated with corrosion on the wire(s) comming off the sender from the tank. Depends on the sender, but some also have a ground wire that is supposed to ground through one of the bolts that holds the sender to the tank. I would check everything back there.

GD

[Cougar]

To find out what is causing this problem with the alternator it would be very helpful to have a voltmeter to test with. To see if the ground is the problem check the voltage between the engine ground and the negative battery post. If things are good the voltage should be close to zero. Be sure to check the small wire from the positive battery post and make sure it is ok. A bad connection there will cause this trouble. Also make sure the fusible links are making good connection as was suggested.

[Durania]

I am going to redo the connection on the battery part of the alternator, its about to fall off as it is. I believe this could be the cause of this. I am going to redo it tomorrow because I simply don't have the pliers needed to crimp it.

[Cougar]

If you are talking about the main output connection of the alternator having this problem you may be correct. All connections need to be well made anyways. The main output lead has to carry a lot of charging current so it is very important that the connection is well made and has very low resistance to the battery post.

[Durania]

Cougar thanks for confirming my suspisions, we check the current at the battery and it was good. I hope me fixing this tomorrow can clear alot of that stuff up.

[GeneralDisorder]

I like to run a 4 guage "battery cable" from the output of the alt directly to the positive terminal of the battery. The stock wires usually look pretty bad after 20 years, and although I redo the terminal lug also, the extra large wire seems to help especially if you have a lot of high-draw accesories.

GD

[Durania]

I like to run a 4 guage "battery cable" from the output of the alt directly to the positive terminal of the battery. The stock wires usually look pretty bad after 20 years, and although I redo the terminal lug also, the extra large wire seems to help especially if you have a lot of high-draw accesories.

GD

By doing that, all I would have to do is slide the end right on the output part of the alternator? Do I still need to leave the other wire on there? So in the end I will have two wires coming off the alternator output part.

[GeneralDisorder]

Yep - that's how I do it.

GD

[Cougar]

By running a bypass wire like that you are defeating the fusible link that is there to protect the wiring. If that new wire gets shorted to ground somehow you will almost certainly have a fire start. I would recommend you put a inline fuse in the line close to the battery if you do this.

[Durania]

The thing that still gets me is that when driving home at night, my left turn signal has a bit of a fluctuation to it, like theres a hint of light in it. The old man and me are going to try and hunt down some electrical junk here in the next few days. May start by adding some grounds and check the disty. Gas gauge still reads wrong, and wipers are at a crawl. Hope these are all connected.

Next question, can anyway tell me what exactly is the "kick down relay" I dont have a fuse in mine but I did on the hatchback. Whats up with that?

[GeneralDisorder]

By running a bypass wire like that you are defeating the fusible link that is there to protect the wiring. If that new wire gets shorted to ground somehow you will almost certainly have a fire start. I would recommend you put a inline fuse in the line close to the battery if you do this.

While that is true, it's no different than the existing 4 guage starter wire the runs directly to the starter lug. Should that short it would probably cause a fire also, but Subaru didn't see fit to install a fuse in that one.....

Or is your point that the alternator circuitry is more likely to ground out than the starter solenoid? Now that I think on it, that may not be a bad idea really.

I have a 60 amp fuse on the 8 guage wire going to my stereo amp, but then it runs through the firewall, and under carpeting, etc. So more likely to accidentally short I would think.

GD

[NoahDL88]

My .02 is that your battery is toast, check your battery voltage, engine off, if its below 11 volts, its draging your voltage down as its so discharged that your alt can't keep up. worst case it will fry your new alternator. I've had this happen at work a couple of times.

Also make sure your battery connections are good, tight and clean, also your fusible links should also be clean and tight. Check for resistance between the battery and the frame, and also from the battery to the alternator power terminal.

[Cougar]

While that is true, it's no different than the existing 4 guage starter wire the runs directly to the starter lug. Should that short it would probably cause a fire also, but Subaru didn't see fit to install a fuse in that one.....

Or is your point that the alternator circuitry is more likely to ground out than the starter solenoid? Now that I think on it, that may not be a bad idea really.

I have a 60 amp fuse on the 8 guage wire going to my stereo amp, but then it runs through the firewall, and under carpeting, etc. So more likely to accidentally short I would think.

GD

GD,
I think the alternator wire is more likely to short out than the starter cable lead. For one, the lead is near the top of the engine where it is easy to get at and if the alternator's internal blocking diode went south, watch out.

[Durania]

Both alternator and battery are doing their job. Had that checked out a minute ago. Sitting in traffic my voltage gauge is around 12, driving down the road it drops dramatically to around 9 or 8. Sounds like ignition coil or distributor to me.

[Durania]

Bump

[daeron]

durania: take the thickest wire going off the alternator (the charging wire) and replace it. It should go up into the fusible link block, find a place where you can make a good solder joint to splice in a new wire, and cut it off. If your battery and alternator are tested as good, and youve replaced your battery cables/terminals, adding ground straps between the battery and the chassis, block and chassis, and maybe even battery to block, and then replacing your charging wire are the next couple weak points to check.

[Cougar]

Both alternator and battery are doing their job. Had that checked out a minute ago. Sitting in traffic my voltage gauge is around 12, driving down the road it drops dramatically to around 9 or 8. Sounds like ignition coil or distributor to me.

The coil and distributor really have nothing to do with this charging trouble. To eliminate the trouble check the following areas. First check the fusible links for a connection problem. If they are ok then check the smaller lead from the positive battery post that supplies power to the car accessories. Also check the connections to the back of the alternator and make sure they are clean and tight. Another possible problem area may be with the alternator warning light in the dash. If there is a bad connection to it then the alternator field will not get the proper voltage. You must check all these things as they effect the charging system.

[Durania]

Whats the first thing that pops in you guy's mind at the thought of voltage getting lower at higher RPM's?

[daeron]

The coil and distributor really have nothing to do with this charging trouble. To eliminate the trouble check the following areas. First check the fusible links for a connection problem. If they are ok then check the smaller lead from the positive battery post that supplies power to the car accessories. Also check the connections to the back of the alternator and make sure they are clean and tight. Another possible problem area may be with the alternator warning light in the dash. If there is a bad connection to it then the alternator field will not get the proper voltage. You must check all these things as they effect the charging system.

yah, what he said. and what I said before that. coil and distributor have nothing to do with voltage, other than eating it.

[daeron]

Whats the first thing that pops in you guy's mind at the thought of voltage getting lower at higher RPM's?

increased heat, or electrical load (charinging or draining,) or vibration, from higher RPMS causing a ground to fault. Or, a non-functioning alternator. But, given that the alternator is definitely good, see above.

[Durania]

If I can get up off my butt in the morning I will go out and start inspecting all my grounding points on the brat. I might even run to wal-mart and pick up a bigger ground for the ole' bag. Ill definetely check my fusible links, I had enough trouble out of them on my hatchback from where I got excited the day I bought it and put the replacement battery in backwards!