When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Good evening boys and girls I am having a recurring charging system nightmare .I have an 86 F-150 4.9 so far I have replaced the alternator, battery, both alternator plugs both battery terminal cables,starter, fender mounted starter relay and I have checked all charging system wires for continuity. The alternator has an internal voltage regulator and it was new with the alternator.
The alternator has worked intermittently but the strangest part to me is that if I disconnect the positive terminal the engine runs smoother, squealing from the belt goes away and the alternator works perfectly. Also when the alternator is functioning under normal running condition the engine does the same thing. Please help I think I'm loosing my mind
Lots to digest here. Kinda like having a basket of deep-fried jalapenos just before riding the Tilt-A-Whirl, but I digress.
Rule #1: With an alternator, NEVER run the engine with the battery disconnected. Amongst other duties, the battery acts as a giant capacitor to smooth the normal peaks of the alternator output. Without the battery, you can get massive voltage spikes that can damage the alternator or any electronic modules.
Rule #2: See rule #1
Rule #3: See rule #1
Before any further troubleshooting, charge the battery. Beg, borrow, or steal an automatic charger with at least a 10 amp output. A trickle charger won't cut it. Charge the battery at least overnight so you know it has a full charge. Don't skip this step. It's very important.
There's a good chance your new alternator is now toast. Check for AC ripple (a failed diode) with a voltmeter. Put the black lead on the alternator case. Put the red lead on the alternator's output, the insulated stud with the big cable. You'd think it wouldn't matter, but you won't get the same reading at the battery. Measure directly at the alternator. Start the engine and set the meter to DC. You should see around 13.5VDC. Now switch the meter to AC (not a typo, alternating current). Start with a high range and work your way down. Any reading above 0.5VAC means you've got a failed diode in the alternator. Play around with various electric loads. Try minimal loads first, the turn on the lights, fan, etc. The reading should always stay under 0.5VAC.
Since your alternator is internally regulated, it's possible you've got a ground issue. Run a voltage drop test between the alternator and battery.
First check the ground side, since that often gets overlooked. Set your meter back to DC volts. Put the black lead on the alternator case. Put the red lead on the battery's (-) post. Not a typo, red lead on the negative post. Go directly on the post, not the clamp. Run the engine and load up the electrical system. If the alternator is properly grounded, you should see less than 0.5VDC. Anything above that indicates a unwanted restriction in the ground circuit.
Next check the positive side of the circuit between the alternator and battery. Put the red lead on the big insulated stud on the alternator. Put the black lead on the battery's (+) post. Once again, not a typo, black lead on the positive post. Run the engine again and load up the electrical system. If this side of the circuit is good, you should see less than 0.5VDC. Anything above that indicates an unwanted restriction.
Try that and get back to us. Charge the battery overnight, and then ten minutes to run those three tests. And don't forget rules 1-3 above.
Lots to digest here. Kinda like having a basket of deep-fried jalapenos just before riding the Tilt-A-Whirl, but I digress.
Rule #1: With an alternator, NEVER run the engine with the battery disconnected. Amongst other duties, the battery acts as a giant capacitor to smooth the normal peaks of the alternator output. Without the battery, you can get massive voltage spikes that can damage the alternator or any electronic modules.
Rule #2: See rule #1
Rule #3: See rule #1
Before any further troubleshooting, charge the battery. Beg, borrow, or steal an automatic charger with at least a 10 amp output. A trickle charger won't cut it. Charge the battery at least overnight so you know it has a full charge. Don't skip this step. It's very important.
There's a good chance your new alternator is now toast. Check for AC ripple (a failed diode) with a voltmeter. Put the black lead on the alternator case. Put the red lead on the alternator's output, the insulated stud with the big cable. You'd think it wouldn't matter, but you won't get the same reading at the battery. Measure directly at the alternator. Start the engine and set the meter to DC. You should see around 13.5VDC. Now switch the meter to AC (not a typo, alternating current). Start with a high range and work your way down. Any reading above 0.5VAC means you've got a failed diode in the alternator. Play around with various electric loads. Try minimal loads first, the turn on the lights, fan, etc. The reading should always stay under 0.5VAC.
Since your alternator is internally regulated, it's possible you've got a ground issue. Run a voltage drop test between the alternator and battery.
First check the ground side, since that often gets overlooked. Set your meter back to DC volts. Put the black lead on the alternator case. Put the red lead on the battery's (-) post. Not a typo, red lead on the negative post. Go directly on the post, not the clamp. Run the engine and load up the electrical system. If the alternator is properly grounded, you should see less than 0.5VDC. Anything above that indicates a unwanted restriction in the ground circuit.
Next check the positive side of the circuit between the alternator and battery. Put the red lead on the big insulated stud on the alternator. Put the black lead on the battery's (+) post. Once again, not a typo, black lead on the positive post. Run the engine again and load up the electrical system. If this side of the circuit is good, you should see less than 0.5VDC. Anything above that indicates an unwanted restriction.
Try that and get back to us. Charge the battery overnight, and then ten minutes to run those three tests. And don't forget rules 1-3 above.
Not the best at electrical and trying to keep up. I don't have a output stud on the alternator it has a three wire plug two of them are joined and run the starter relay and one runes to the choke. So should should I pierce one of the wires to test it tight after it cone out of the plug or upstream a little bit after they are joined?
I don't have a output stud on the alternator it has a three wire plug two of them are joined and run the starter relay and one runes to the choke. So should should I pierce one of the wires to test it tight after it cone out of the plug or upstream a little bit after they are joined?
I prefer to pierce a wire only as a last resort. Two things you can do instead of piercing.
You can backprobe the connector, as explained here:
Use extreme caution, as that wire always has hot battery power. Be careful the pin doesn't contact ground.
Edit, lined through inaccurate info:
The other option is to connect your meter lead at the choke. The wire from the alternator to the choke? It will act as an.extension of your meter lead. I'd probably go with that option if it is easier to access than backprobing at the alternator. Warm up the engine to fully open the choke. With the choke heater warm, you can disconnect it for a couple of minutes to run the tests. It only needs to be disconnected for the AC ripple test. You can reconnect it for the voltage drop test between the alternator and battery.
The alternator has worked intermittently but the strangest part to me is that if I disconnect the positive terminal the engine runs smoother...
Another quick test is to remove the alternator drive belt. If the alternator had been pumping out lots of AC ripple, it will stop doing so if not spinning. The battery must be fully charged, as it will be supplying all power, but you should be okay for a quick test drive around the neighborhood.
Yet another test, this one with the belt still on. When the engine is acting up, play with the electrical loads. If unloaded, turn the heater fan to high and turn on the high beams. Sometimes the extra loads help smooth out any excessive AC ripple. Other times, the alternator only acts up under a heavy load, so try reducing the electrical loads and see if that makes a difference.
Why not just get a meter and put it on the battery with the engine off and write down that number, and then start the engine up, with the alternator connected and turning, and check the battery again. Write that down and report back.
That's on an '88 F250, but I think your alternator is the same style. Does it have the big connector on the side? If so, those are notorious for being damaged by heat and arcing. Check the alternator side for damage, too. Here's a close-up, from the third to last picture in the article above:
Guys when did Ford start using ALT with an internal REG in our trucks?
IIRC even the 3G ALT has a large output stud to the battery for charging but he said his does not? So how is it charging the battery all be it sometimes?
I think he needs to take a picture of the back side of the ALT and of the inside fender well to see what is mounted on it.
Dave ----
Note the two B+ wires, joined together at splice S204.
The third wire feeds the choke as previously described, but I was less correct than usual about the internal connection. Unfortunately, it can’t be used as a test point when checking for AC ripple, as I had suggested in post #5.
Note the two B+ wires, joined together at splice S204.
The third wire feeds the choke as previously described, but I was less correct than usual about the internal connection. Unfortunately, it can’t be used as a test point when checking for AC ripple, as I had suggested in post #5.
Thanks for the information, learned something new today.
So the fire starter 2G ALT has the connection only on the side of the body.
My 1G has a 2 wire plug on the side and the BAT on the back. I also have installed a 1G that has all the connections on the back.
Thing is my truck wiring is the 2 wire / 1 BATT so had to make an adaptor harness to make it all work till I go with a 3G ALT.
Dave ----
Be sure you have 3 wires on the voltage regulator plug on the 2G ALT.
Originally Ford just had 2 wires, newer Voltage Regulators need all three inputs to work.
Jim
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Slideshow: Called the Fortress, the 850-horsepower pickup combines Raptor underpinnings with military-inspired features, survival equipment, and a starting price of $285,000.
