Battery goes dead

[Dave.S]

I have a 3550 HST tractor and recently the battery keeps dying when parked. I disconnected the - cable and put a test light between the cable and battery. Test light glows brightly. I pull every fuse one at a time and any relays I could find by the radiator and each time the light did not got out. I even removed the wiring to the ignition switch and the light still stays on.
any ideas as to where to look for the draw? Also I am looking for the wiring diagram for the tractor. I found one in the service manual but the PDF is unreadable.

 

[Roadworthy]

If you replace the test lamp with an ammeter you can determine the amount of draw. That may give you some idea of where the current could be leaking.

 

[alexpops]

Try jiggling/massaging the harness at any sharp turns, tight attachment spots or places it goes through the firewall while you watch the test light. You probably have some worn/torn insulation & a short inside the harness between two wires. If that doesn't reveal anything, next step is to open up the harness & see if you have worn wires ... can be a long tedious process that might get sped up with an infrared thermometer to identify hot spots in the harness.

 

[Dave.S]

Thanks for the replies I'll try both. how much amperage is acceptable? I know the computer needs to keep going and I checked all fuses with a test light with the key off the on fuses with power were the flasher lights and I think the ecu.which are the the bottom left fuse for the hazard light circuit and the top left the one I can't remember what circuit. When I put my multi meter between the cable and - terminal it read full battery voltage.
any Ideas about where to get a wiring diagram?

 

[alexpops]

Depending on how long it takes the computer to go to sleep, with everything off, you probably don't want to see more than 15 or so milliamps, and down around 5 would be better. If you are seeing higher draws than that, you have a short, wiring problem, or a stuck component switch. You said pulling fuses didn't change the test light, so, if it was me, I'd concentrate on the wiring before the fuse panel, and check for any spots that could be shorting to ground. Then, you could also try disconnecting components one at a time to try & isolate the problem, starting with the alternator/voltage regulator.

Have you load tested & visually inspected the battery itself? I had a chevy tahoe with relatively new (2 year old) battery that I was convinced had a parasitic draw problem, based on the same results you are showing (dead after 20 hours, voltage differential between post and cable, fluctuating amp draw north of 1.5 amps) but I couldn't find a bad circuit. When I pulled the battery, I saw significant swelling on one side that was hidden while it was bolted into its box. Wound up being an internal short between plates in the battery. Battery load tested well initially, then didn't.

 

[Dave.S]

I think I may disconnect the alt just to see if the test light goes out and check for pinch points in harnesses for shorts.
Alt charges at around 14 volts and battery will start motor if unhooked when done working for the day and starts motor when using tractor in the field,
but is an old battery marine deep cycle that I used on a kart for jump staring. hard working on electric gremlins with out a diagram so I know what circuits have power all the time. Thanks

 

[CDBUG]

An idea,
I had a similar issue with my Mahindra 2538.. turned out to be the Ground Strap to the frame. Took it off, cleaned both ends to spotless.. and the related connection on the frame where it connects, with a grinding wheel .... no issues since

 

[DonRybak]

Dave, not sure if you tried the alternator yet but my bets are on the diode inside it being shorted. Fairly common on vehicles.

Good luck...........

 

[teddybaham]

i have a 3550 pst cab, i had your exact symptoms for a few months. i chased all the things you did. i could run the tractor and battery would charge and re-crank after running even with A/C. (in hindsight not nearly as well as i thought). it falsely led me to believe i had a parasitic draw. turns out the $200 interstate battery less than a year old AND testing at 12.4 volts was only making 300+CCA. it's rated for 950 CCA. check the battery. i purchased a battery tester on Amazon for $20 but Harbor freight sells the viking one for $40. pull the battery charge overnight then test. new battery tested @ 1049 CCA. <stays hot and spins that motor right over. Glad my fix was this simple, hope yours is too. if this isn't the problem there's a wiring diagram in your user manual. if you dont have that, go to mahindras website under owner resources you can type in your serial number and get the manual in a PDF. save that file to your phone to keep.

 

[ultrarunner]

Sad state when batteries that should be in their prime are not.

For decades starting in the 70’s we sold Interstate and very rare to have any issue.

Sadly the last few years before we dropped them had problems and Interstate would blame modern vehicles with always on electronics…