Looks like the strange noises and and falling battery amperage problem with my 91 Jeep Wrangler is solved!
Turns out it wasn’t the alternator, but a broken idler pulley.
So, if your idler pulley looks like this, you’re going to have a problem.
And… here’s the serpentine belt diagram for the 1991 Jeep Wrangler YJ 4.0.
Thank-you Charles for fixing this!
The engine light came on in my 91 Jeep Wrangler. So, my buddy/mechanic showed me how to find the fault codes. It’s a clever little trick that I never knew!
The “Key Tricks”
Older (OBDI) models – Start with the ignition off. Within five seconds, switch the key on, off, on, off, on. (“On” is NOT “Start” and “Off” is NOT “Lock”). The “check engine” light will flash. Count the flashes. Each code is a two digit code, so a (for example) 23 would be FLASH FLASH (pause) FLASH FLASH FLASH (long pause). It will never flash more than 9 times, so watch for those pauses!
My Jeep flashes these codes: 12 35 76 21 47 55
Here’s a site that shows the computer codes for my Jeep:
http://go.jeep-xj.info/HowtoECUcodes.htm
Looks like it’s time for him to come over and get me fixed up.