Hi everyone,
I have a 97 f-150 with a 4.6 and an auto. I bought the truck a month ago and the amp gauge has never worked right. It usually doesn't register at all and if you hit a bump or hit the dash it will bounce up then go back down. Driving home from work the other day the battery went dead. I replaced the alternator with a used one that I know worked good, now 2 days later and it's back to the same way. Is there anything else I need to check out before taking this to a dealer? Does the amp guage need to work right in order to complete the charging circuit? Any help would be greatly appreciated as this is my work truck. Thanks

 

I'm not sure if the amp gauge is a part of the cicuit or not. If it is, it would have to be in series with the load, and if the amp gauge is in series with the circuit, and if it's not connected, then that would leave the circuit open. Thus causing the current to stop flowing to the alternator. I really don't know what I'm talking about, but when you said when you hit the dash, the amp gauge bounces up. That shows right there that there is "continuity" or current flow through the gauge itself when you hit the dash. Sounds to me like a loose connection at the gauge. That's what I would check. Sorry if I'm no help.

 

Hi again,
Thanks for your help. I have done a search and found some people suggested a megafuse could be at fault. Any idea were this fuse is, what it looks like and were can I get one? Thanks again.

 

Never heard of a Mega fuse. But from the sound of the name, it sounds like one of the "larger" fuses under the hood in the little black box next to the fender. Just a guess. Again, sorry if I'm no help. I hope you can fix it without taking it to the dealer. That hourly labor is very costly. Hopefully someone will come along that knows what their talking about and give you some help.

 

I would definitely check all the fuses and yes, the wiring for the gauge will make a difference in the alternators ability to charge the battery.

 

Hi, and thanks for the feedback. I took the alternator and battery and had them tested, both check out perfect. All fuses are good. There is no power to the ignition side of the voltage regulator. I have been told that a faulty gauge shouldn't affect the charging system. I don't know were to go from here. Can a faulty ignition switch cause this problem? I plan on working on it more tomorrow, and if I can't get it working then it's off to the garage. Thanks

 

There is a fused feed from the Ignition through the Instrument Custer to the Charge indicator light to the voltage regulator. This signal is used to turn on the Voltage Regulator. If the fuse is blown the alternator will not charge. The fuse is a 10 amp and it should be #19 in the Central Junction Box. It will read Instrument cluster, Air Bag Diagnostic Monitor. If the fuse checks out you will need to pull the connector at the alternator and test the light green with red stripe wire. It should have 12v in the start and run position. If it does not post back and I will show you a diagnostic for testing that circuit.

Regards

Jean Marc Chartier

 

Hi everyone and thanks for the replies. I fixed the truck today. It turns out that the #19 fuse in the main fuse box under the dash was loose and not making a proper connection. The blades on the fuse weren't contacting properly. I pulled the connector off the voltage regulator and stuck it with a test light. I then turned the key to run position. Had a buddy jiggle the fuse a bit and the light went on. All I did was to bend the blades on the fuse and now I have no problem. Never would have thought that. I appreciate all the info on this. I would have been clueless without all your help. I'm just glad my truck is back to normal. I own two 97's and wouldn't trade them for anything. Thanks again, Ivan

 

It's good to hear you got it fixed.

 

Glad to see it was something simple.


JMC