Electical Issue

[farm]

Ok guys my class c is driving me batty...  Somewhere I have a short and can't find it..  I'll open the drivers door and the courtesy light will come on, then I put the key into the ignition and the buzzer goes off but as soon as I turn the key no light, no buzzer anymore and of course it won't start.  Nothing nada etc.  But if I use jumper cables or a jump box it'll fire right up.  The battery is brand new so I know it's not that best I can figure is I've got a short somewhere any ideas?

Thanks

Roger

 

[99WinAdventurer37G]

As it's an 89, I would suspect the cable.  It's not cheap, but I'd replace the cable from the battery to the starter and to the ground.  You could try just taking them off and cleaning all the connections and reconnecting first, but I find that with age, conductivity decreases.  It's worked for me in the past on old vehicles.

 

[Lou Schneider]

If you're connecting the booster directly to the battery terminal clamps, and the engine starts OK with the booster, you've eliminated just about everything from consideration except the battery and it's connections to the cables.

If you have some corrosion on a connection, you can often can draw a little current through the bad connection.  But when you increase the load by turning on the ignition the corrosion chokes off the current flow.

Besides a bad connection between a battery terminal and it's clamp, you could also have corrosion building up between the clamp and where it attaches to the cable.  Battery acid fumes can infiltrate even clamps that are molded onto the cables, and the bolt on replacement clamps are even more vulnerable.

Or you could have a bad battery - it's possible to break a terminal free from it's connection inside the battery by putting too much wrench pressure on it.  Or the battery could be internally defective.

You can have the battery load tested at any battery shop.

 

[John Canfield]

If you have some corrosion on a connection, you can often can draw a little current through the bad connection.  But when you increase the load by turning on the ignition the corrosion chokes off the current flow.

Exactly.

 

[afchap]

I had almost the exact problem years ago on a Ford van. Cleaning the cable connections would work for a few days, then no start again. I finally found one of the cables was caught between the exhaust header and the frame. Insulation was melted and I had a direct short. As suggested above, I would look for a cable problem.

 

[bucks2]

And I'll bet that when you find the problem it's on the ground side.

Ken

 

[farm]

Thanks for the replies I'll check the cables tomorrow!!

 

[Irover]

Another quick check is the cables going to the solenoid especially if you have the Ford type. Corrosion between the cables and nuts is hard to see. Just because a battery or any other part is new does not necessarily mean it is good.

 

[farm]

Ok I didn't get to the cables today, but while I was out and about I got to thinking if it was a cable issue then when I hooked the jump box up it logically shouldn't start if it was the cables.  It would seem like the battery eventhough it's less than a year old would logically be the problem..

 

[bucks2]

Ok I didn't get to the cables today, but while I was out and about I got to thinking if it was a cable issue then when I hooked the jump box up it logically shouldn't start if it was the cables.  It would seem like the battery eventhough it's less than a year old would logically be the problem..

And if you can't push your car by yourself, then two people pushing shouldn't be able to move it either?????? If you add battery capacity then you have more energy pushing thru the wires, corrosion, rust, loose connections and whatever else might be faulty. I think your logic is probably wrong on this one, but then again I could be wrong.


Ken

 

[99WinAdventurer37G]

Ok I didn't get to the cables today, but while I was out and about I got to thinking if it was a cable issue then when I hooked the jump box up it logically shouldn't start if it was the cables.  It would seem like the battery eventhough it's less than a year old would logically be the problem..

And if you can't push your car by yourself, then two people pushing shouldn't be able to move it either?????? If you add battery capacity then you have more energy pushing thru the wires, corrosion, rust, loose connections and whatever else might be faulty. I think your logic is probably wrong on this one, but then again I could be wrong.


Ken

Ohms are resistance to the flow of power from the battery to the device requiring the power.  By the addition of the jump with jumper cables, the volts increase, volts are the force that push the power through the cables.  So if cables are corroded, or there is corrosion in the system connections, the standard battery does not have the force (volts) to push enough power through the system to the device requiring power.  So by giving it a jump, the extra volts push more power so that the unit starts.  Then you drive around thinking your charging you batteries enough to start it next time.  But do to the corrosion, more volts are necessary to get the power to start the motor.  You can go to some of the auto parts store for a free load test on your battery. If it passes, replace the battery, if you replace the battery and it still isn't right, replace the cables, which should fix your problem.  Think of it this way, a corroded cable is like a half inch hose, a clean new cable is like a one inch hose.  Obviously you will get more water in your bucket with the one inch hose.  The same is true of cables, a clean cable can make a poor battery seem good.

 

[Lou Schneider]

So by giving it a jump, the extra volts push more power so that the unit starts.

You don't increase the voltage by connecting a second battery, you increase the available current. The voltage stays the same.

If you have a bad connection that's restricting the current you can pull through it, adding more current capacity ahead of it won't make any difference - it still won't pass any more current.

That's why connecting a second battery directly to a bad battery's terminal clamps eliminates everything after that point - if the engine starts with the jumper battery in place, the rest of the wiring is OK and the problem has to be either in the original battery or it's connection to the clamps.

Or to use a water analogy, if you have a kinked hose, you won't get more water out of the far end by putting a larger hose between the faucet and the kinked section.  You have to fix the kink.

 

[Gary RV_Wizard]

Lou,
I think he meant that voltage is increased when you jumper a strong battery to a weak one, i.e. the jumper source battery is at 12.6-13.6v whereas the jumped battery may be only 10-11 volts. A weak (discharged) battery will typically be low on both volts and amps.