Hey guys I have a 79 250 4x4 and need to boost her every time I want to start her. Its like there is just not enough power. I think I might have a draw somewhere??? I have changed and added all grounds ie; batt. to block,block to body and frame to firewall. as well as my + batt cable and starter cable but still nothing Im thinking maybe the alternator?? is there anywhere else that is common for these trucks? btw I put a load test on my battery and it's reading ok however its only just above 12 volts I read somewhere they need 13.6 or something is this true? I also put disconnects on the batt to keep it from running dead when not in use. Any help would be greatly appreciated!!!

 

MiddleNameMUD,I had the same problem years ago and it ended up being a direct short inside my radio.I disconnected the ground cable from the battery and hooked up a test light lead to the neg post on the battery then put the probe end to the body. If the test light comes on then you have a direct positive short to ground somewhere,do not forget to turn the key on all functions for this test.The light may come on very dim depending on the type of short.Hope this helps.

"bowties in the rearview mirror"

 

and if that is the case there is a procedure to test the truck to find where the drain is coming from...


How to find a parasitic drain
You might ask... what's killing my battery?
Using this proceedure should get you started in the right direction.

Disconnect the positive battery cable and put a test light between it and the positive post. IF you have a drain, the light will light.
Now start pulling fuses until the light goes out. TAKE A PICTURE OF YOUR FUSE BOX FIRST! you will want to put the fuses back in their correct positions (different colors are different amperages)
Then start putting fuses back in. If the light comes on, keep that fuse out and continue installing the rest of the fuses.
AT this point you may have one or more fuses out of the box, you will need a wiring diagram to see what components are on those fuses. Then you can start disconencting the components to take them out of the circuit, and then other connectors in the circuit, until you can narrow down where the short is. Be aware that there are some circuits that will be hot all the time, and create a little draw, such as the clock radio, and keep alive memory for the PCM, perhaps others.
Note: Using this method justaguy found a stuck relay. He said, "So I used your advice and used the test light. I went though all of the fuses and the relays again. I climbed up and took the wires off of the glow plug relay and then the air heater relay, thats when the light dimmed. I replaced the relay... so far so good!"

Here is a great tip
When you disconnect the battery you may break a parasitic connection. How I do it is connect one lead of the test light or meter to the cable being removed and the other end of the test light or meter to the center of the post of the battery.Then I slide the cable off the post and I never interrupt the connection.You will find far more draws this way when you don't break the circuit.


special thanks to Poppy and BogHog at Fordforumsonline

hope this helps.

 

Great thanks guys I do have a short somewhere, I did that test light check totally by fluke last week as I could't start the ol'girl I was checking my solenoid and set the test light on the fender rail and it came on. I grounded the batt. and it started. I had no Idea how to trace it though, fuse block! makes perfect sense. I'm going to try that tomorrow, thanks a lot I'll keep you posted, wish me luck!

 

You disconnect the NEGATIVE cable and test from there...

Josh

 

Bad diode will give you a reverse field draw from the alternator. Simple info is to find an auto parts store or garage and have them test the battery, starter, alternator, and a draw test too. Do it everyday at work.

 

Well I started on the wiring today,"fun to do in the rain"lol.
I fixed a test light to the body and to the disconnected batt. ground, the light came on to indicate a short or draw. I started pulling fuses one by one and after all were out the light still remained. I went directly to the batt and followed it to the alt. it all looked good. It wasn't till I unplugged the three wire trailer style connector that it went out does this mean the alt has puked out? I was going to take it to get it tested tomorrow or wed. Am I wasting my time or should I just get a new one?

 

If disconnecting the alternator made the light go out, it sounds like a diode has shorted in the alternator and is drawing current backwards as DKW suggested.

 

Ya I figured as much im goin to do an upgrade and put a 130 amp alt in then be done with it! thanks for the help everyone.