Suddenly tonight I notice that my battery light is lit and the charging guage is showin about 9 amps!
The truck continues to run fine and I make it home ok.
Now I realize that it has to be only a few possible things. I first check the connections to the battery. I removed the positive cable and the truck shuts down immediately. I cleaned the terminal connections. Figuring that my truck won't start now, because the battery was not charging, I am surprised that it starts right up!?!
Now I am confused.
Could the battery be no good? I think the alternator is fairly new. But, I just bought this truck a month ago, and know very little about it. A friend who is a mechanic had mentioned that it was a new alternator when he saw the motor.
How do I best determine the reason for this apparent electrical problem?
Your help is appreciated...thanks.
~F

 

First thing is to see if it is really charging. start your truck and use a volt meter on the battery and see what it is reading. with the truck running it should read between 13.8-14.5 volts. if it is not I would start at checking the alternator. your dash gauge is probly reading 9 volts not 9 amps. there is a big differance.

Good luck
Scott

 

[updated:LAST EDITED ON 14-Jun-02 AT 00:55 AM (EST)]A really GOOD way of getting to pay for a NEW alternator or Systems Computer,is to Unhook battery cables while the engine is running.

Try using a Multi-meter instead.

EDIT: Maybe there was some corrosion on the + Battery cable causing resistance.When you put back on it scored the corrosion.


[font color=red]Dennis

Calgary,Alberta,Canada[/font]


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[font color=blue]78 F-150 429CJ,Silver,Explorer Pkg.
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You can run your truck a long time on a good fully charged battery, so the fact that it started right up does not supprise me at all. As above a multi-meter is the best way to check alternator output but having already done some troubleshooting the hard way this is what I get. If the battery is the only source of power, removing the positive battery cable should make the engine quit as it did. If the alternator was producing power the engine would have continued to run. Most alternators are rated for at least 75 amps, plenty to run your truck. You have a bad alternator. Not to worry its just 2 bolts and a couple of electrical connections. Now, you don't say what year truck you have. When you get your replacement alternator it should come with a new set of connectors for the electrical connections. PUT THEM ON! The factory wiring was undersized on late '80s and early to mid '90s trucks. Fires have been started due to this and there is nothing sadder than watching your truck burn when you could have prevented it. The meter on your dash is a volt meter not an ammeter. It being down around 9 indicates that your battery charge is indeed low. You will be walking before very long at all.

 

First, thanks for the help...
Today I was able to start the truck up still, but left it home just the same.
I need batteries for my meter and although it seems like the prevailing determination of the board, I will still check my alternators output. The battery is a Diehard Silver, so that would probably have a few starts left.
Now my questions are these:
Do I rebuild my altenator?
Do I buy a new one, and if I do, what amp altenator is best?
Mine is a 1988 F150 XLT Lariat 302, with power windows, ac, etc.
I realize that buying from a chain store is probably not a good idea, but what about Napa's Motorcraft line?
Does anyone know what the dealers cost would be?
Thanks!

 

no don't try to rebuild it it is possible to put new brushes in some but by the time they wear out the bearings are not to far behind I would just go to any autoparts store and get one that is rated the same as your truck, unless you plan to add alot of extra's (ie. winch, off road lights, booming stereo, etc.) the stoke amprage one should do you fine. I did say volt meter, because I wanted to make sure that you knew to put your multi-meter on the volts setting, not amps or ohms. some peopel still have meters that only do one function. definatly check the out put at the battery first. there are alot of places that check charging systems for free around here that might be a good place to start if you are not sure how to test it, they can also test your alternator after you take it off to make sure it is the problem when you go to get a new one.

Good luck
Scott

 

I notice that your first post states that you possibly have a new alternator. I would check its wires very carefully. It may not have been installed properly. If it is indeed faulty, and has been replaced recently, there is something causing it to fail. I went through three replacements in about 18 months before I realized that I had a small coolant leak, which was dripping on the alternator. It apparently caused it to cook itself.

That was on my 92 F150. The 88 F150 I have had a similar problem. The alternator went out shortly after a heater hose replacement, and a close check showed the same problem - leaking coolant on the alternator.


Winford

 

I do really enjoy the forum, and the help is appreciated!
Here's an update...
I have spoken to the Ford dealer, and they need to know what amps my current alternator is rated at. They say it's on the housing, but it looks as though I will need to remove it to find that out. The 75amp replacement is $165.00. Not so bad IMO.
I haven't had time to test with my meter, but I did look at the situation a little while trying to determine the amperage. I noticed that hoses right above the altenator have been replaced recently. Keep in mind that I bought this truck wholesale, and know nothing about it previous. I have speculated that possibly when replacing these hoses, some fluid might have entered the alternator...? While poking around, and moving the hoses aside I then noticed that two of the three wires from the plugin have worn away and I can actually see the wire! I don't know if the clamps (which BTW, are Ford clamps, which to me mean that the work was done at a dealership) might have touched these exposed wires! Maybe that could've contributed to my situation as well...I dunno.
I do really like this truck, and went into this knowing that my project would take me down some unknown paths...of course I received my new window motor today too!!
Looks like my weekend is all planned.

 

Just to wrap this topic up...
Today I installed a new altenator, (Motorcraft 75amp, $55.00 thanks to my nephews discount!) I also replace the original plug that had been worn away. The new connector has a much thicker wire to it than the original one. All is well with the charging system.
I also replaced my faulty drivers door power window motor. Had to drill out the dimples, but it went very smoothly.
Thanks again for all that contributed to my posts.
Let's see...what's next...?