I recently had a blown fuse which completely disabled my transmission. After replacing the fuse, the transmission is fine, but I have a high pitched whistling coming from what seems to be the alternator. It may not be the alternator, but it is one of the pulleys because I removed the drivebelt and it stopped. Also, the engine (4.6L) is now mifiring. I reset the computer and the SEL hasn't come back on, but it seems like the truck isn't running on all 8 cylinders. I have never had any engine or transmission problems so I find it odd that all of this would happen at the same instant. The alternator was only 3 days old when this happened. This is the second alternator of that brand I have had (the first was defective when I bought it) so I do not have too much faith in it. Is it possible that the alternator put out too much and fried electrical components? I have never heard of such a thing and I assume there are safeguards against it in the electrical system but I can't think of any explanation.

 

The safeguard is INSIDE the alt, so yes, it's possible your problems came from the 1st alt &/or the 2nd. It's also possible that the problems caused by the 1st then damaged the 2nd. Please tell me they aren't coming out of "the zone"...


With the engine idling or revved so the miss is MOST apparent, unplug one coil at a time WITHOUT adjusting the throttle. When you find one that has virtually NO effect on the way the engine runs, you've found the one that's missing.

 

Alright I was hoping there was a way to figure out which cylinder was missing so I'll try that. The alternators came from NAPA. God I hate that place. The first alternator tested fine at the store but when I installed it, it wouldn't charge. I took it back and again it tested fine, so I reinstalled it and still it didn't work. I spent about $300 trying to diagnose the problem (I thought it was a problem somewhere else in the electrical system) and buying parts I really didn't need. Ultimately, I lost my job because I missed so many days trying to fix it. Eventually I took it back to NAPA yet again and told them it HAD to be defective because there were really no other possibilities. They hooked it up to their machine and it only put out 9 volts. They gave me another one and everything worked fine for about 3 days.

I did notice that the "working" alternator's pulley turned kind of roughly when I bought it. I asked the NAPA idiot about it and he said that all of them did that. I didn't belive him but I had to get my truck working and it really didn't seem like a huge deal. If it broke I would just get another free one. So I assume this is where the whistling is coming from.

I the voltage regulator is bad, what exactly should I be worried about as far as the engine goes? Would excess voltage just "fry" one or more of the coils or would I be looking at a more complex problem?

Thanks for the help.

 

Thers two alternater models for that truck a 90 & 130amp - It doesn't matter , coils are probably a little weak and grown attatched to the weaker alternator. May even have had a powersurge , doesn't take much if there weak and ready to be replaced . Are they the originals ? If so , that's incredible they lasted this long. great stuff!!.. Good luck!!

 

I've only had the truck for about 8000 miles so I couldn't tell you if they're original. The alternator that I have is the 130 amp, although I don't know what the old one was. I'm going to check the coils and alt output today. It's kinda cold out though so we'll see how long I actually stay out there lol.