MikeC4

A few days ago, I noticed that my battery was not being charged by the alternator. The battery voltage measured around 12.7V on the digital readout, and the analog needle just stayed in same position. I immediatley drove the car back home.

So here is what I did:
1) Removed ALT. from car and had it tested. It failed all 3 tests on the Autozone test machine.
2) Bought a rebuilt from Autozone
3) Installed rebuilt ALT. Same problem as before. Battery was not charging with engine running.
4) Removed battery and found that the ALT. wire fusible link was blown.
5) Bought a 14 gauge fusible link for GM applications and spliced it in(soldered, not crimped). Length of fusible link is about 5 inches long.
6) Put everything back together, Ohm'ed the Alt. wire from BAT teminal to end that connects to fuse block, and it was 0 ohm as desired. I started engine and ALT is now charging battery to about 14.7V.
7) After idleing for a minute or so, the fusible link gets hotter than a firecracker to touch.
8) shut engine off, let it cool down. Start engine, fusible link starts to get real hot again. Hot enough to burn your finger if you touched it to long.
9) After letting the fusible link cool down, I also did another test by holding the red wire at the BAT terminal on the ALT. It was not hot to the touch.
10) I shut off the engine before blowing the new fusible link.

So:
-The Alt. wire is 12 gauge
-The fusible link I bought is 14 gauge (2 sizes smaller than the wire being protected)
- Everything in car functions fine during the short time I run the engine.

Any ideas why the fusible link is getting so hot ? I am almost certain that the new fusible link will blow if I run the engine long enough.

I am thinking about having both the Alt. and Battery tested. Could the Alt. current limiter be bad ??? ( I am always leary of rebuilt electrical stuff).

Please advise......

toptechx6

With both ends of this wire disconnected you should also check it for continuity to ground using your ohmmeter. The resistance test you performed does not rule out a short.

cdreece

You should get the right size fuseable link if you can one with a 12 gauge wire. The 14 gauge wire is going to get hotter than the 12 gauge wire because it is trying to pull more current through it than it was intended to do.You can always go with bigger wire and have no problems as long as you have the correct fuse but going with a smaller wire is a big NO NO.In alot of car stereo appliacations they upgrade the wire (they call it the big 3 upgrade) from the battery to the starter the starter to the alternator and the battery ground to 4 gauge or bigger for better current flow.

and yes you could have gotten a bumb alternator also since it was a rebuilt one.

MikeC4

Fusible links are supposed to be 2 gauges smaller than the wire they are trying to protect. If I splice in a 12 gauge fusible link to the 12 gauge Alt. wire, this would defeat the purpose of a "fusible link".

jfb

Your battery is slightly discharged and with a working alternator, you are experiencing normal but high charging current which will decrease as the battery charge comes up. If the fusible link is supposed to be #12, then you should replace it with #12 NOT #14. It is normal for the battery wires to become warm right after engine start because the short 100+ amps the starter motor draws, makes the battery to temporarily look like a badly discharged battery and the initial charging current is quite high which warms the wires on the battery.

M. Schumacher

Shouldn't that be four gauge sizes smaller? If I read your message correctly and you are referring to the largest wire coming from the plug in connector then it should have a black fusible link. That is in fact what my 96 coupe takes.

http://whiteproducts.com/fusible-faqs.shtml
http://whiteproducts.com/fusible-specs.shtml

Take two aspirin before clicking this link...

http://oljeep.com/gw/alt/edge_Alternator_Theory.html

MikeC4

jfb.....Thanks....you were dead nuts on. I removed the #14 fusible link and replaced it with 5 inches of #12 F/L. When I started the car, the 12 gauge F/L got "warm" to the touch and after a few minutes, the wire began to cool down. It never got real "hot" like the 14 gauge. So it makes sense that upon firing up the engine, the current demand would be at a peak due to starter demand and a lower static battery charge.

Here's where I totally FUBAR'ed by using 14 gauge F/L :
The mistake I made was thinking the main Alt wire was 12 gauge. So I immediatley said "hah, I need to use #14 gauge to protect it". I don't have a wire gauge so I eye-balled it. I could not read the gauge number on the red wire due to limited access or perhaps laziness. The main Alt. wire is 10 gauge, and the blown out fusible link was 12 gauge(I could actually read 3.0 sq. mm on a small section of the blown out F/L . So using a #14 F/L to protect a #10 gauge power line is not a good idea.

Thanks again for your insight regarding high currrent demand at startup !!!

MikeC4

All the literature I have read says that the F/L must be 2 sizes smaller than the wire it is intending to protect and that the length of the F/L should not exceed 9 inches.

Thanks for the links. Nothing like getting a crash course on Alternators and fusible links....

M. Schumacher

Blue (12 ga) is the correct one for the main feed cable. I didn't think that was the one you were working with because I knew that cable could not be 12 gauge. I don't want to flog a dead horse. but I think it's bigger than 10 gauge. Anyway, you got it fixed which is the important thing.

MikeC4

Hey, I don't mind if we into the ground... I just want to get this job done correctly. I appreciate all your insight.

So, are you saying the BAT wire coming from the alternator is 8 gauge and not 10 gauge ??

M. Schumacher

Mike, considering the size of the alternator (over 100 amps) and the current carrying capacity of various wire sizes, 10 gauge doesn't seem like enough. However I went out and took a look at mine and the wire doesn't look that big. You may be right.

- Tony