Guages/ Charging problem
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Guages/ Charging problem
Talk about an electrical nightmare.
1975 Ford f-250 4x4 W/ 390, Manual 4sp, and NP205
I got the truck, and no lights worked, only the guages. I went on to find simple solutions and fixed the lights. then all of the sudden I have no lights, no guages, and no charging. (well the alternator puts out 12.3, just enough to keep her runnin)
I've solved my blinker/brake problem (thanks to an awesome tech article on here) Bad switch.
The alternator tests strong at 15v. and the regulator is new. I did a quick check of the wires under the hood and no obvious cracks or breaks.
Still have no guages. Not sure where to start.
Any Ideas ford-fans
Thanks
SPC 91B
Hotshot
Joined: Apr 2009
Posts: 14,333
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From: Stanley, VA
First, DO NOT RELY ON THE STOCK FORD AMMETER!!!!!! These are notorious for not working. Even when the trucks were new the ammeter was a POS. Ford actually released a technical service bulletin on the subject.
Are you checking the voltage at the battery or at the alternator output?
Check it at the battery, it should be about 14.7 Volts, if it's not check it at the alternator. If the voltage is okay then there is a wiring problem. If it's low then the problem is probably either alternator or regulator.
You said the alt tested strong @ 15v. Was that on the truck or on a test bench?
Are you checking the voltage at the battery or at the alternator output?
Check it at the battery, it should be about 14.7 Volts, if it's not check it at the alternator. If the voltage is okay then there is a wiring problem. If it's low then the problem is probably either alternator or regulator.
You said the alt tested strong @ 15v. Was that on the truck or on a test bench?
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the alt was tested on a bench, 15v stong. I tested at the batt. on the truck. (always with an external voltmeter, never the guage.) besides all I have is a light.
What would I probe to check the output at alt? this external volt reg is new to me.
thanks
What would I probe to check the output at alt? this external volt reg is new to me.
thanks
Hotshot
Joined: Apr 2009
Posts: 14,333
Likes: 247
From: Stanley, VA
On the backside of the alternator there are three wires, black, orange and white (I'm going from memory here). The black is heavier gauge than the other two. This is the wire that runs to the battery. I believe the terminal on the alternator is marked "BAT". This is the terminal you check for voltage.
The black wire goes from the alternator to the battery side of the starter solenoid. This wire has a fusible link in it. If the link is blown the battery won't charge. The fusible link is located towards the solenoid end of the wire and has a tag that says "fuible link".
To check the link, grab the wire on either side of the link and tug on the wire. If it stretches or feels soft the link has burned out and is no good.
These can be replaced by splicing in a new link. The links are available at any parts store, just be sure to use the same gauge as original.
Here are some pictures of the alternator wiring harness showing the fusible link.
The black wire goes from the alternator to the battery side of the starter solenoid. This wire has a fusible link in it. If the link is blown the battery won't charge. The fusible link is located towards the solenoid end of the wire and has a tag that says "fuible link".
To check the link, grab the wire on either side of the link and tug on the wire. If it stretches or feels soft the link has burned out and is no good.
These can be replaced by splicing in a new link. The links are available at any parts store, just be sure to use the same gauge as original.
Here are some pictures of the alternator wiring harness showing the fusible link.
Hotshot
Joined: Apr 2009
Posts: 14,333
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From: Stanley, VA
If your going to fab the harness you might think about adding an aftermarket ammeter and/or voltmeter. Now would be the time to do it.
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well i'm in luck, I will probably do that eventually, but for now it was the wire going to the back of the ignition switch, witch consequently gave power to my fuel and temp gauges. I fixed up the wire, and the alt. light comes on now (and goes off accordingly). but when I put it all back together the gauges went out again, must of knocked something loose
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