Wow, thanks JasonL :cheers:

So, going with, say a 40 amp fuse, would melt the wire before the fuse would blow.

 

I'm still wondering if 30A is too little or too much. :D

Here is how it is wired at the moment...


Alternator ---> 10 Gauge ---> 30A Circuit Breaker --> 12 Gauge ---> Jumpstart Junction Box

 

Scorp-

Have you positively ruled out a shorted cell in your battery? I had this happen to me, and it caused all kinds of weird problems with the alternator. If you haven't tried this yet, swap a different battery in there. A shorted cell may be causing the alternator to freak, then blow the link.


[Modified by fullboogie, 9:25 AM 10/4/2002]

 

Ok, here's my hypothosis:
First, when your starter cable was loose, it may have wiggled enought to contact a ground somewhere thereby blowing fusible link C. If in fact FL-C is a 12 guage link, the current through that is very likely more than 30 amp... more like 60 amp before it blows.

When you measured for continuity, did you disconnect the battery? Most meters will show contunity if you measure voltage accidentily. It would be the same thing as putting your leads across the battery terminals. Was there any resistance at all??

 

Yes battery was disconnected when I checked. Very very very low resistance, nearly none. I wonder if I should try to buy a handful of Fusible Link C's from chevy today, maybe I just do not have a strong enough breaker on it?

 

What happens when you disconnect everything from that post? Measure for continuity one lead at a time.

 

Scorp,

I may be off in left field, but I will tell you what happen to me once....

I am a mechanical engineer, so electric stuff bugs the heck out of me....

Here it is:

I was in my car about 2 yrs ago, early spring one of the first times out with it. I pulled out of McDonalds when the car started acting really wierd. I pulled into a stereo place a buddy of mine owns and shut the car off. When I did I saw smoke coming out of the hood. I ran into the store and grabbed their fire extinguisher and returned with a few people following. We opened the hood and the smoke was gone....Wheew!

Upon examining the car I spotted right away the main cable, the one you are having a problem with (I think) had eroided right off, just as it leaves the FI harness on the drivers side. It runs out out to the alternator and I drained the battery.

For a quick fix my buddy went into his store and grabbed some heavy duty cable. We ran it from the altenator to the + battery terminal. Jumped the car and everything was fine. It was suppose to be just temporary, but has become a perminate fixture :bb

Perhaps you could run a temporary cable and see if it fixes the problem? I am not sure if this is a viable idea with everything you have done so far, but perhaps you have a problem with the cable or where its connecting in the junction box....

Good luck :cheers:

 

I've often wondered about that too. We have alternators with 100 amp capacity and 10 guage wire!! 30 does sound small but you have to respect the fact it worked before. If you flip your readout to voltage and start it what does it say? If you got a bad alternator the regulator could be letting the voltage run wild which would blow the fuseable link. Also remember that if you use an ohmmeter to check for continuity between positive and ground you will see some continuity due to the circuitry that stays alive all the time (burglar alarm, ecm, etc.) We're talking about 1000,s of ohms though.

 

If I jump the alternator to the battery directly it works perfectly fine and charges the car.

 

Is your voltage 13.8? Going directly to the battery-- the battery would except it like a quick charge while protective circuitry would shut it down.

 

well then it have to be that wire or that juction box behind the battery, right? I would disconnect everything from that juction and track each one to it origin..one of them has to be shorted to ground...

Or just leave it the way mine is...its been perfectly fine for 2 yrs now....

Have you tried running a new wire from the alternator and instead of going to the battery's +, going to the junction box and see what happens...

 

Under what conditions?

Right now if I disconnect the battery totally I get 11.65 volts at the battery (keep in mind I've been running the car on battery alone for a while). It is an Optima Redtop battery. If I connect the battery and keep the car off and test terminal S on the 3-wire connector on the alt I get an identical reading. Testing the 10 gauge wire at the alt also gives an identical reading. As soon as the car is started, the 10 gauge wire to the alt blows the circuit breaker.

If I put a lead directly between alternator to battery it starts to charge and holds at about 13.0 which I consider normal because the battery is low. Normally if I lose an alternator and have to charge the battery up a little with the alt (bad bad i know) it will hang around 13.0/13.3 and then be back up to 13.8/14.1 within a couple hours of driving.

Who knows, maybe my whole problem is that the breaker isn't big enough? I wish we knew for sure. :(

 

That I have not done.

 

I gather it is the 3rust line that you blew the link on. It is the line that now has the 30Amp CB in it. The 3Rust line is the Alt output line. (Previous discussion lead me to belive it was the red field (rust1) line that was blown. Please disregard.) That alt is capable of putting out 105Amps constantly.
Do you see the problem here.


[Modified by ZylaRace, 10:12 AM 10/4/2002]

 

30 amp is way less than 105 amp, yes. Thats why I'm confused. I've been saying all along I have no idea what I need for an amp rating at this point. :( Sorry I didn't meant to lead you to believe the field wire was dead in the other post.

The 3 rust fusible link was totally blown on the junction box side. The wire was completely emptied of its contents and seperated from the rubber housing.

 

I'm on the phone with a Chevy dealer, they told me to go to NAPA. All they had was a 16 amp fusible link that comes on a 25' reel that you cut off what you need.

 

i would try that one scorp, maybe that line is damaged and building up resistance. That is what happened to mine because of the corrosion. It burned right through it. There was all kinds of buildup on it....

that will at least let you know if its that line or not...bet it is..You may have damaged it when you were bending the FI harnesses around.

Later!

:cheers:


[Modified by ski_dwn_it, 11:29 AM 10/4/2002]

 

Lets start slow.
W/ the connector plugged into the ALt, the output post empty, engine running, you should have14-16 volts @ the output post to Gnd.

Do you have that?


Yes,..... looks liek the alt is fine. We look elsewhere.

No,.... Check the connector wires. Do you have batt voltage on pin "S"? Is pin "F" shorted to Gnd?


[Modified by ZylaRace, 10:57 AM 10/4/2002]

 

Hey Scorp!!! :seeya

Long time no see... For this one I think the 30 amp is the stock Fus. Link so the 30 amp breaker should be fine. I could be wrong though. From all the C4 vettes I have seen 30a seems to be the norm. However depending on Mods and any upgrades to the charging system this may need a bigger breaker. Sounds to me like something got broken, pinched, snapped or destroyed during the transplant..

Sorry I know not much help but best I can do! :D

 

A 30 amp fuse or circuit breaker is way too small in the output lead of your alternator. The alternator output is limited to 105 amps by the regulator circuit in the alternator and a discharged battery will draw very large current from an alternator until its state of charge increases dramatically. The factory fusible link should be able to withstand the alternator maximum output for short periods. Your jumper works from the alt to batt because it is not fused. Your voltmeter measurements appear normal to me, so I think that your fusible link wasn't rated high enough. For $45 you can buy a dc/ac clamp on ammeter at Sears which will allow you to measure the current in the alternator output wire without breaking it. This ammeter goes to 400 amps full scale. I think I am going to buy one tomorrow just for the ability to measure high dc current without breaking a wire (you can measure starter motor cranking current). This is the cheapest clamp on dc ammeter I have ever seen.
Also, I highly recommend that you leave your battery charger on the battery for a full 24 hours before you blow any more breakers or links.

With the ammeter, you could measure the battery cable current (alternator disconnected) with the engine running (same condx which blows the link). This will tell you if you have a large current draw from the battery with the engine running. Under this condition, the alternator will be putting out its maximum (105 A) current into a very low resistance. With the engine off, the battery cable resistance (battery disconnected) should not be low. There are some circuits connected to the battery that are not fused (starter for one) and one of these circuits may be where the current is flowing to.


[Modified by jfb, 10:57 AM 10/4/2002]