So I was about 20 minutes from school yesterday and my check gauges light came on and then my voltage dropped to the left peg. I made it to school and got it checked but it was still acting weird. It would run 14ish at idle then drop off as soon as I started driving. So my buddy and I took it off and I took it to Autozone today and they said it passed, well I didn't wanna spend 200 bucks on something that wouldn't fix the problem. So we went to Advanced and their tester said it was only putting out 11 volts. Anyways got a new one and got it on and she runs fine again. I guess my question is does the gauge just die as soon as it runs under 12 volts so that the gauge light comes on and warns you or what because it was running like 12 volts then it would just die off. Also the alternator is super easy to change on the 4.7 if anyone wants to know for future reference. All it takes is a 10mm, 13mm and 15mm socket.

 

I don't know for sure but I think you are right, when the alternator output drops to a certain point the PCM probably drops the gauge below 12 volts and turns on the check gauges light as a safety feature to keep from burning up the voltage regulator in the PCM.

I am curious though, how many miles do you have on your truck? I am wondering how long my alternator will last. I have 143,000 miles on my truck and it still has the original alternator.

I think my truck is getting to that age where I have to replace some parts. I had to replace my water pump last month, and now just this past week I replaced both front wheel bearing/hub assemblies. I have brand new BFG Long Trail T/A's with less than 5,000 miles on them and the truck sounded like a 4 wheel drive running big ole knobby mud tires on dry pavement.

I enjoy working on my truck and keeping it in good shape, it has a lot of new parts on it already but I just wonder about some of the OE parts, how long they might last.

Thanks

Jimmy

 

143k on that is awesome. I did my water pump at 80k, bearing hub at 85k and still on original alt at 90k

 

I guess I got lucky with my water pump. The coolant has been flushed and refilled 3 times in the 5 years I have owned my truck. I had a power flush done once around 65K when I was headed out on a trip up tp Georgia, then it has been drained and refilled twice due to accidents. The radiator was replaced each time because of the accidents too. One time I hit a doe deer no bigger than the average good-sized dog and it still did $3,000.00 in damage to my truck, then last year someone hit me in the front end, that one was over $4,000.00 in damage. Maybe the coolant drains and new radiators were the reason my water pump lasted so long. It was still working when I replaced it, but it had a little play in the pulley shaft and was making a scraping/warbling kind of noise, so I knew it was about time to get a new one.

Thanks

Jimmy

 

I had to replace my PS pump but no water pump or alternator yet at 128k.

 

As far as I know it was original, I've only had it since 90K tho and I have 150.5K now. I was pretty sure it wasn't the voltage regulator because the dealer had to put a new PCM in it when I got it. I'm just glad I got it figured out and it was easy haha. The one on it was a Denso one...is that what they come with stock?

 

I guess so, mine is a 117 amp Denso. Thanks for the info.

Jimmy

 

It should be a Denso, 136 amp.

 

Yeah it was a 136A Denso, so unless the dealer replaced it I guess it was original.