1998 Ford Mustang Alt 20 amp fuse blows intermittently

Hi
Think problem is in battery to engine ground left front engine. OHM from ALT body to batt NEG should read 0 Ohms. If connection or cable poor as engine heat and load increases so does AMP draw from increased resistence in ground circuit so fuse melts.
Let me know
Thanks for donate

Docfixit, please check my OHM readings and let me know if it confirms your thoughts. Engine warm, but not hot. Engine off: case to battery negative terminal .5 to .75 OHMs with the meter set at 200. Engine running: Ohms at 9.0 to 10.0 with meter at 200.
Thanks in advance for your reply.

fatman

Not good replace cable go with a little larger diameter. Clean block contact area well and batt term.
Let me know what out come is.

Docfixit, OK I know this may be becoming a bit tedius, but The Ford replacement cables are $229 and I haven't found any aftermarket direct fit cables. This setup isn't just a simple cable, it has other grounds and power feeds coming off of it so before I went further I wanted to double check my readings. First of all the first readings were from a digimeter that only goes down to 200 on the scale. I double checked it with a old style volt/ohm meter. After checking for 0 at the meter I found 0 with the engine off and .5 on and 1.0 with a/c, blower fan on medium, and engine cooling fan on. Correct me if I am wrong, but I think the 200 scale on the digimeter is misleading. The 10 I had with engine only running on the digi when divided by 200 equals the .5 with the old style meter.

If this all is correct, where do we go from here?

fatman

Let's try a simple experment attach jumper cable to NEG then to clean block connection. ALT good spot. drive around see if fuse stays

Docfixit, sorry been busy at work. So jumper cable to clean connection at the block and then from there to alt body? How large does the "cable" need to be? Like a batt cable or test lead wire?

fatman

Battery cable size like a set of jumper cables

Replaced neg and pos cables also ground strap from block to chassis and cleaned all connections Ohm reading the same have not given it a good hot run yet Nothing was real dirty but thought i'd replace it as car is at 100k The whole package was very tightly bundled and a real pain in the butt to r&r

Yea think they need to make Enginers have to repair the stuff they design be alot easier I bet.
Hope that is the fix keep me posted

Well, it was hot here in Tucson today so I got to see how it did completely warm with the a/c and blower on mid. It blew the alt field fuse again!