Weird Voltage problem

[Gruff511]

Okay well to start off the other day I put on a New GM 1 wire alternator. Everything was driving and acting normal. I was running at a solid 13.6v for about 2 days until last night I went to start the car and my +Volts were at 10v!! and when I would try to keep the engine running the volts would drop down to around 8v and the car would start trying to shut off on me. When I turn the car back off the battery Volts would be at a normal 12.8v. The battery was tested and was checkout out to be good. I decided to leave it alone and the next day I got a brand new battery and tightened the alternator belt a little more. That seemed like it solved the problem but now my volts wont go any higher then 12.2 at the battery while the car is running. I know this is enough for it to run but why would the alternator be putting out 13.6v one day, then not work the next, then work but only put out 12v?
When I test the voltage at the alternator while running im getting 0v!! Im completely stumped! IDK if its the alternator or something else?

 

[clang1114]

Sounds like its the voltage regulator. To be honest I've never actually just swapped a voltage regulator on a dsm. But I work on VWs and Audis for a living. It is possible to swap just the regulators on those. This is usually what happens with voltage regulators. They overcharge sometimes or they undercharge, or they don't charge at all.

 

[92boostinawd]

^ x2

 

[Diamond Star Werks]

dsm alternators have internal regulators.

 

[Gruff511]

Sounds like its the voltage regulator. To be honest I've never actually just swapped a voltage regulator on a dsm. But I work on VWs and Audis for a living. It is possible to swap just the regulators on those. This is usually what happens with voltage regulators. They overcharge sometimes or they undercharge, or they don't charge at all.

Well the voltage regulator is inside the alternator because it is a 1 Wire self exciting alternator. But I wouldnt think that a 2 day old alternator would just stop all of a suddenly how it did.

And Also I dont have the stock ecu anymore im running Megasquirt ms3 full standalone.

 

[NHerron]

What do you mean by 0V at the alternator? If you're referring to the thick cable running off the alternator known as the "B" terminal and you're getting 0V there, then that's your problem. The alternator B terminal is not hooked up, therefore not charging anything

 

[Gruff511]

What do you mean by 0V at the alternator? If you're referring to the thick cable running off the alternator known as the "B" terminal and you're getting 0V there, then that's your problem. The alternator B terminal is not hooked up, therefore not charging anything

Yeah I read 0.60v on the thick cable on the alternator! But it still seems to be keeping the battery at 12v right now? I dont get that WTF

Ill be taking the alternator off and putting on a different one to see if that solves my problem. Ill take it to get tested also to see what wrong. Hopefully Ill get it figured out tonight.

 

[NHerron]

I haven't personally done the swap (-plan to later) but if you don't have any output at the "B" terminal, then the alternator sounds like it aint doin' squat. Battery may be full @ 12V now, but still sounds like alternator isn't outputting and everything is reliying on the battery right now

When you got 8V running and then 12.8V when car was off, that's normal, in a way. When the battery is under load, internal resistance of the battery results in a lower output voltage. For instance, check the voltage right now. Now, turn on the headlights. Voltage should drop a good bit. It's the alternators job to take care of that

A load test puts a load on the battery (X amount of amps) and records the voltage drop during that time to determine what condition the battery is in

 

[Gruff511]

Okay so your right it was the alternator. I put the other one I had before back on and I'm getting 15v out the alternator but I'm only getting 11.7v at all my controls. I pin pointed the issue to be an electrical short in my fuse box.

 

[Anubis_4_99]

dsm alternators have internal regulators.

2G N/T's have an external regulator located in the ECU.

 

[NHerron]

Nice! So how is the swap? Just have to grind a little metal off the alternator case itself I heard.. and a little adjustment to wiring at alternator area correct? Everything is simple bolt on after that?

 

[Gruff511]

Nice! So how is the swap? Just have to grind a little metal off the alternator case itself I heard.. and a little adjustment to wiring at alternator area correct? Everything is simple bolt on after that?

Are you referring to the GM 1 wire alternator I first mentioned? If that, then yes I just had to grind off some metal but mounting it to the block was really simple, it aligned to the block pretty well so I made a 1/4" steel bracket to bolt from the block to the alternator I think I have some pics I can post.
But the alternator I put back on that works is the Saturn alternator. the GM one is the one not working.pos

 

[NHerron]

I was actually assuming you were using the Saturn mod I keep hearing about ...but will the GM one will interchange? Chevrolet Suburbans with the one wire alternators are everywhere around here...I could snag one cheap too

 

[Gruff511]

I was actually assuming you were using the Saturn mod I keep hearing about ...but will the GM one will interchange? Chevrolet Suburbans with the one wire alternators are everywhere around here...I could snag one cheap too

Do you have the same 4g63 in your profile? because if you do then im not sure how they will fit on a 4g63. On the 420a its a pretty simple mod I will post up some pics when I get home.

 

[NHerron]

Whoops I guess I ASSumed you were 4g63 N/T with Turbo swap

I didn't know 420a guys used the Saturn alternator too? Is that setup complicated, wiring wise with the regulator located in the ECU? Anyhow... ya if you can, post some pics!

 

[Gruff511]

Whoops I guess I ASSumed you were 4g63 N/T with Turbo swap

I didn't know 420a guys used the Saturn alternator too? Is that setup complicated, wiring wise with the regulator located in the ECU? Anyhow... ya if you can, post some pics!

Well both my Saturn and GM alternators are 1 Wire self exciting alternators so theres no need to wire them to the ecu. You just wire the +Volt from the battery straight to the alternator.


Heres my link on the Saturn Alternator install....http://www.dsmtuners.com/forums/mai...-saturn-alternator-install.html#post152984336




The bottom bolts directly to the block with a homemade brace

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Well back to the Topic. Im pinpointed the electrical short to the fuse box. Im reading a lot of resistance at the 2 10A fuses that are labeled radio and room lamp. IS THIS NORMAL TO READ RESISTANCE ON THESE FUSES?!
Also im getting quite a bit of resistance at my 30A Ignition switch. IS THIS NORMAL?!

Here are pics of which ones im talking about....

These are the radio and lamp fuses Im getting alot of resistance from.

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And this 30A ignition switch also....i cant figure this out =(

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[NHerron]

Nice guide ... oh and I feel retarded again. I remember reading that write up a couple months ago

I have a couple emissions codes on my setup right now and plan on making a remedy for the codes. I'm figuring out how the codes are set and am working on a way to bypass them

Anyway I'd imagine on your guide you or someone else will eventually have that check engine light taken care of Haha I hate mine being on all the time..bugs me




**Just saw your update. How are you taking these test? Not sure I follow why you would test a fuse for resistance

 

[Gruff511]

So checked the continuity of the circuits it turned out to be the dome light on my rear view mirror. I guess something is shorted out inside the mirror and it was causing a short circuit. I just unplugged the light