Batteries drain unless block heater is plugged in

So the issue only occurs at <=40 degrees. Truck should start fine even without the grid heaters at those temps.

First thing I would do is check the battery rest voltage after it sits all night at those temps. You want to see 12.4, but 12.2 is acceptable. If it is less than that there is probably a parasitic loss somewhere. If it is at 12.4 but cranks slow you can check the voltage again after the attempted crank, if it dips below the 12.2 then you proved a battery issue because you just performed an old school load test. If the battery voltage looks good the entire time then you need to start measuring resistance at all the cables, including the grounds.
 
Just a thought, but I'm wondering if your grid heaters are shorted some where and kill your batteries as soon as the solenoids bring them on. At any rate that would be very easy to rule out.

Another thing that is related, your alternator does not charge when your grid heaters are running
 
the batts bad..one of em has a bad cell..even if theyre testing good I can tell ya the batts are bad..my truck did almost the same thing. one bad cell is puliing down the others. try doing only one batt..either one one at a time...itll star easy with the good one and hard with the bad one
 
Dual battery systems are only as strong as the weakest one. New starter contacts will also help. I've done mine twice, still original starter.
 
I like to keep it simple stupid or the KISS method when checking battery/starter problems.

If the problem only occurs when it's cold and the block heater is not plugged in, I'd let the truck sit under the same conditions, then hook it up to your other running truck with good jumper cables and then try to the start the cold-blooded truck. If the starter cranks at normal speed and the truck starts, you know its a battery/low voltage problem. If the truck cranks slow, you know at a minimum the 2 month old starter is weak and struggles with the heavier load of cranking over a cold motor.

Before replacing the starter, I like to inspect the cable ends (both the heavy power cable and the trigger wire) for major corrosion as well as swap the starter relay with the fuel bowl heater relay or a spare just to make sure the relay for the trigger signal wire isn't weak. Replace the starter if all of these areas check out and it still cranks slow. With a running truck and jumper cables, you'll be feeding the starter 13+ volts so it should crank faster than normal despite the cold motor. If it turns the motor even remotely slow, there's a problem.

My untested theory after reading your account is that without the block heater turned on, the intake temp sensor is low enough to require the grid heaters to cycle. If you are in the habit of cranking before the wait to start light goes out, you are then using a large chunk of ampacity on the grid heater elements and you'll experience more voltage drop than usual at the starter. Combine that with a hard to turn cold motor, possibly weak starter, possible high resistance cables, possible weak starter relay, possible burned starter contacts, and you end up with a motor that won't turn over.
 
I did some more looking and on the starter the signal wire post I can spin it like who ever installed it over tightened it and broke it loose inside would this be the problem? I was thinking that if that post was broke free and able to spin it that it woukdn't do anything, am I thinking correct or not?
 
How old are the batteries and are they leaking out the top. Honestly sounds like brain
F&@?ing bad batteries.
 
If the starter is kicking out and engaging and spinning then the signal wire is doing its job energizing the solenoid. You could do a voltage drop during cranking across the two large posts on the starter to see if the solenoid itself is chewing up more voltage than it should be
 
No the batteries aren't leaking out of the top and the one battery is probly a couple monerjs old and the other probly couldn't be any older than a year.
 
don't matter..batts go bad...if one is got one bad cell all the rest of em will suffer...swap em out.....

disc one and try it on each one separate...itll be obvious if one had a bad cell
 
mtboggs said:
No the batteries aren't leaking out of the top and the one battery is probly a couple monerjs old and the other probly couldn't be any older than a year.
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Ahh... well it is highly recommended to replace them in pairs. When I used to work on DC power plants with battery backup's we usually replaced the entire battery string if one battery was found defective. Failure to do so usually meant the immediate degradation of the new battery, and decreased the life of the existing batteries. Charge and discharge rates were different between them and they all naturally degrade to the lowest common denominator. Should be easily testable in your scenario, but they have to be load tested separately, and preferably after 12 hours of rest, and at the same temperature you experience the issue. I would still expect one of the batteries to have a low rest voltage of 12 volts but they have to be separated to see that.
 
Batteries these days do not last. I am not an old timer but it seems like in the past 5-10 years batteries have gotten pretty crappy.

You really should replace both at once in these trucks as well. Replacing one at a time usually costs more in the long run because you are chasing one killing the other over and over.

As mentioned before one bad cell makes for a bad day all around. They can get to the point where you can't even jump start the truck.

edit:treed
 
left field... But , when was the last time you changed your oil?
 
got it figured out a while ago, been a while since I've been on hear. I took every ground off the truck and cleaned them and on one of the battery grounds I found plastic or something melted around the cable so it wasn't making a good connection, cleaned it off and haven't had a problem scenes
 
mtboggs said:
got it figured out a while ago, been a while since I've been on hear. I took every ground off the truck and cleaned them and on one of the battery grounds I found plastic or something melted around the cable so it wasn't making a good connection, cleaned it off and haven't had a problem scenes
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What ground?
 
lorendiesel5.9 said:
Somebody forgot to take the plastic cap off when installing the battery.
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I've done that once. Replaced a battery in the dark, left the black negative cap on there. Only difference I had a no start, no nothing in the morning. :nail:
 
Bad connections will cause lots of hair pulling look for corrosion, just a thought don't overlook the obvious.
 
mtboggs said:
got it figured out a while ago, been a while since I've been on hear. I took every ground off the truck and cleaned them and on one of the battery grounds I found plastic or something melted around the cable so it wasn't making a good connection, cleaned it off and haven't had a problem scenes
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Win slow said:
Bad connections will cause lots of hair pulling look for corrosion, just a thought don't overlook the obvious.
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Late to the party bud.
 
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