dropin voltage at start ? HELP !

[strokin 187]

OK so this is my first time on here looks like a cool site So here is my prob i took my truck about two and half weeks ago to get the oil changed. After an hour of waiting they told me I needed a new fuel filter and also a rear cab bulb out, so I said OK. So they did all that and changed the oil went out to the truck, started the truck everything seemed fine. About four days later I started to notice that my voltage gauge was reading half or a bit lower than half. And then I also noticed when I went to start the truck that the voltage dropped down to eight on the gauge and the truck keeps acting like its not charging the batteries properly. So I put two new batteries in the truck and it still does it! Put a brand new alternator in the truck and that wasn't it either. So now I have no idea why the voltage is dropping. The truck still starts but barely! If anyone has any idea where I might look next for this problem any help would be appreciated! Thanks!

Brandon
Ford for life!

 

[DaveBen]

First off, Brandon! Now we need to know what truck you are referring to? Year and model please. What modifications have you done? And what is the values of the voltages you are referring to? Saying "half" of what it was, is not helping us help you.

Dave

 

[BIG JOE]

First off, Brandon! Now we need to know what truck you are referring to? Year and model please. What modifications have you done? And what is the values of the voltages you are referring to? Saying "half" of what it was, is not helping us help you.

Dave

What Dave said..

 

[Dieselpwrdredneck]

check the alternator with a multimeter. should be 14 ish when its charging correctly. let us know what ya get and we can go from there

 

[strokin 187]

The truck is a 1999 F250 Super Duty Diesel 7.3L no modifications what so ever, the truck is bone stock. When I refer to half on the battery gauge I am refering to the stock gauage which 18 is the highest 8 being the lowest, and then there is a picture of the battery and in the gauge and the needle hovers right between the battery on the gauge. So, right in the middle basically and when I hit the key it drops to 8. The truck is a 4 X 2. Hope this helps.

 

[DaveBen]

When you hit the starter, the draw is the highest. I would expect a voltage drop, but not to 8 volts. Maybe 10 or 10.5 volts. You have the glow plugs heating AND the starter creating a big draw. You need to monitor the voltages using a volt meter. Factory meters are not accurate.

Dave

 

[DaveBen]

If all of this is still going on, you may need an alternator. Don't get one at any of the Chain Auto Stores, they are junk. Try these guys: High Output Alternator, 200-250-300-350 Amp Alternators, high output alternators, GM,Ford, Chrysler Dodge Alternators Several of the guys on here use them and like them a lot.

Dave

 

[Dogman]

I get the starter checked too. It could be pulling more power then needed to start. Does it sound like its turning fast or have a drag to it.

 

[strokin 187]

it drags slow then just barley starts someone else told it may be a starter issue i just thanks to all though 4 all the help

 

[DaveBen]

From what you posted this morning, it sounds like the starter is going bad. Slow starts is a clue since you have good batteries. Take it out and have it tested.

Dave