12 replies to this topic

[Seabronc]

If it doesn't show a charg when running, I would suspect the alternator. Voltage reg maybe but probably not. Check battery terminals and connections. The alternator goes to the same terminal on the start solenoid so check that connection also. IF you put a voltage meter on the battery positive terminal and have a good 12+ volts then the start side of the solenoid is suspect including the starter. If you can get it started check the voltaage on the plus terminal, it should show about 13.5 with the alternator running if not the alternator probably is bad. I'm not susre on your year Bronco right off hand but the voltage eg may be built into the alternator.

Goof Luck,

[Seabronc]

PS You may also have a bad battery that won't hold a charge.

[sweepersrgr8]

Did you change the alternator harness(2 black/orange, 1 white/black wires)? Ford had a recall on these, the wires didn't stay in the plug and would push out during reattachment, just barely making contact.

I had this same problem, and had to get a jump every time I shut down, bought a new battery, same thing after a couple days. My truck had a new ALT, but had it tested anyway, it was OK. The new harness' come with the new ALTs, and the dummy that installed my ALT just threw it in the console.

I had been wondering what the hell that harness went to. Fixed me right up.


WARNING: I have seen some ALT brands say that there alt doesn't need the new harness, that they have fixed the problem with their plug. WRONG! The problem is on the harness side, unless they came to your house while you were sleeping and fixed your truck....this is not possible.

[Justshootme84]

The problem sounds like the starter solenoid on the fender by the battery. Drive it for 20-30 minutes, then turn the motor off. Check the solenoid to see if it's hot, just be careful not to burn your fingers!!! If it's even warm, get a new one. $15 with lifetime warranty. Check the alternator and it's wiring as well, like stated.

[Seabronc]

From the sound of what you just posted, I'd say it is definately the alternator. It should be well up to running those things. Once the truck is started, normaloperation is for the altinator to run everything while recharging the batttery if necessary.

Good luck,

[Justshootme84]

I agree, you can get a bad alternator since they are usually rebuilt ones. The 90 models have an interrnal voltage regulator, so check that as well.

[sweepersrgr8]

Start the truck, then disconnect the positive battery cable. If the truck shuts off, you have a bad alternator. Also check the condition of your belt, your tensioner should have a gage stamped on it, if the pointer is out of the "good" range, replace the belt regardless of the condition. Keep the old one as a spare, you may need it to get you out of the woods on night.

[Seabronc]

If you use a voltmeter, you should get about 13.5 at the battery when the truck is running, if the alternator is putting out.

Good luck,

[Justshootme84]

Disconnecting the positve battery cable with the engine running is a good way to check if the alternator is charging on older trucks, but I would not do it on computer-controlled engines. I have had several mechanics tell me that it could damage the computer or ECM.

[Justshootme84]

I suggest your next step is to have the charging system checked while the engine is running to see if you still have a big amp draw. The voltage should only drop a tad (0.5-1.0v) when using items like the lights, AC or radio. It sounds like the alternator cannot keep up with that current draw, so you either need a bigger alternator or need to find that problem. Check the ground for the ECM, and the wiring in that area of the harness for anything loose or broken.

My problem turned out to be a bad battery, as it wouldn't hold a charge for very long. IT would go dead after a few days. I put a meter/tester on the truck and found nothing wrong. The battery was 2 years old ,Interstate brand, and my 2nd one in 4 years. I now have a bigger one from Walmart with about 750 cranking amps. You might take a look at the size and age of your current battery, too.