HI My Friend has a 77 Ford 150 with a 400M motor Truck starts and runs. When you shut it off and come back later to start it again the battery is dead. Replace battery identical problem with new battery. Where do we start? Thanks Ross
The battery is probably not being charged. If you have a volt meter, test the voltage across the battery terminals with the truck running. The voltage should be in the neighborhood of 13.8 to 14.3 volts, if the alternator is working normally. If it's lower than that, the alternator may be bad, or the voltage regulator may be bad, or both. Hope that helps.
Thanks for all the advice New development Now when he puts a fresh charged battery in and attempts to start it barely turns over and then drains out very fast. All wires are hot to the touch. He is planning to pull the starter and test. Any other thoughts would be greatly appreciated. Thanks Ross
I don't like this method. The voltage regulator was not really designed to control voltage when there's no "capacity" in the system. Buy a VOM. If the alternator is good it'll put out 13 or 14 volts. And remember, 50% of life's problems.....
Why do you say that? Those were the good old days when it came to repairing electrical problems. Granted they were a lot more common but also easier to figure out. In the case of a battery drain it almost has to be an alternator, regulator, dome or glove box light. A few minutes unhooking the alt. and regulator and pulling fuses should narrow the problem down to the offending circuit. I suppose it would be a nasty job if there is two inches of hog shit on the floor though...lol. Bob
Yea, I would check the alternator first. Like he said in the other post, pull the big red wire off the alternator and try it. No need to pull the starter to test it if it comes to that. Just pull the hot wire off and see if it still does it. But a shorted diode in the alternator seems more likely. You have a near direct short somewhere...No doubt about that. If it turns out not the be the alternator, you will have to look for any possible wires that might be grounded out, or a circuit or device drawing way too much current. I've never had to do that, but if I did, I would probably yank all the fuses first, and test. If ok, then I would replace each fuse one at a time until I found the bad circuit. If it did it even with all the fuses out, the short to ground would be from the fuse box to the battery somewhere. Normally though, that would fry a fusible link, or whatever...So I kinda doubt it's that. Like he said, it's a PIA, and you should hope your alternator diode/s are shorted out. Makes things much easier to fix. :/ MK
Well if it has a bad regulator you would guess that the electronics will fry anyway wouldn't they?. Please don't insult that way , on a 84' Ford F250 there isn't that much electronics in it so there coudn't be that much more in a 77'. Starter has been known to cause those kinds of problems, selenoid could be getting stuck. Alternators don't put out more than 18 volts max which most electronics should be able to handle that. Aleast I know enough about working on my own trucks not to have to hire a mechanic unless it involes complete engine over haul which I haven't had the pleasure of doing yet. I still like this group
yeah and if you have a BAD regulator, you'll FRY the electronics
Here's the update thanks for all the help still in need!
Took Alternator in had checked found it to be BAD.... Replaced with new. (cha-ching) New Voltage Regulator... (cha-ching) With freshly charged NEW battery (cha-ching)... Engine hesitantly started and ran fine. Pulled Red lead cable off battery terminal and engine DIED... Battery now drained. Engine won't restart just turns over 1/2 turn then nothing. Suggestions?
This leaves me a couple of different things to check that I can think of...
Ignition Switch Short Starter Solenoid Short Open in the Alternator return path to the battery
Go back to where you got the alternator and explain to them you unhooked the battery cable and the alternator does not work!!! Most auto parts stores have a tester and will test your charging system for free.
Engine doesn't like to start but once started the voltage at the battery terminals is 12.40v and slowly drains about .01v every 10 seconds , indicating running off battery only and once turn off the battery is too weak to restart engine.
If the problem was in the starter, starter solenoid this would be consistent with a hard start but once started would have no effect on the battery drain. If the problem was in the alternator, voltage regulator this would be consistent with battery depletion but should have no effect on the starting.
It's hard to guess, but you may have a short or wires grounded out. It sort of sounds like you stuck the new alternator in it, and it promptly fried. Just a guess though...I'd yank it and have it retested. You say the engine doesn't like to start/crank? This is either low battery voltage, corroded wires or connectors, or a starter on the way out. If a fresh battery still does this, something is obviously not right. MK
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