Burning Through Solenoids

[JCBAS]

I have an issue on a 1990 36 volt Marathon that has been upgraded from resistor coil to solid state Alltrax SR500 controller, MZJ400 HD solenoid and HD F&R switch. Battery pack is in good shape, holds a full charge and is less than 2 years old.

I have burned through 2 MZJ400 HD solenoids in the past 6 months. The first solenoid lasted for less than 10 hours of runtime and the second one lasted for less than 1 hour of run time.

In both cases I got a pre-charge failure code on the Alltrax controller and no click on the solenoid. Scotty B was great and super patient with helping me troubleshoot the first solenoid issue and we figured out the solenoid failed.
I purchased a second MZJ400 solenoid and when it failed I ran through every check and test that Scotty B told me to when the first solenoid went bad. Everything pointed back to the solenoid failing again.

Scotty mentioned making sure the solenoid is not left on when the cart is not in use and I don't think that is the issue because I always hear the solenoid click on and off. He also said to make sure the wiring wasn't causing the solenoid to be powered at all times, but that's not the issue either. (Scotty's conversion kit makes it super easy with only one wire/cable per solenoid terminal: battery main positive to big positive terminal on solenoid, big negative terminal on solenoid to B+ on controller, blue wire for electronic pedal to small positive solenoid terminal, and small negative solenoid terminal to black male connector on controller).

I was hoping to get some extra insight before I spend the money to burn through another solenoid.

[Volt_Ampere]

Are you buying the Chinese copy JZJ400? They are crap.

[JCBAS]

No, the first one was included in the solid state upgrade kit.
The second one was through a different golf cart vendor.

[Volt_Ampere]

Closeups of them with the writing on the solenoid?

[ThreeCW]

Is it the pull in coil that is burning out on the solenoids ... or are the main contacts being welded together ... or both?

Some resistance measurements on the small posts and resistance / continuity measurements on the big posts will help you to determine the failure method if you have not done so yet.

Some of the Chinese manufactured components can be hit or miss.

[Volt_Ampere]

I had one fail after two years and it was the pull-in coil that failed. The reason it failed was the switch that opens when the solenoid pulls all the way in did not open and that caused the pull-in coil to overheat and short. The reason the switch did not open was that the plunger that pushed the switch got mushroomed over and no longer extended far enough. Poor materials IMO. The contacts looked perfect. The contacts on these solenoids should really last a long time - the make and break are done with minimal current draw. The pre-charge resistor keeps from having a current surge when the contacts close.

[JCBAS]

I'll try to take a picture and post it when I get home.
The solenoids both failed on the low side. I would get battery pack voltage to the small positive terminal, but I wouldn't get battery pack voltage across the small terminals when I pushed the pedal.
Scotty B helped me exhaust every other possible culprit besides the solenoid, but it came down to a solenoid failure on the activation side.

[JCBAS]

Here is a picture of the solenoid. I know the resistor is not on the solenoid, I took it off because it was getting hot just being on the solenoid without using the cart. The right side of the picture is the driver side.

[Capt. Lenny]

Have you considered getting rid of the Chinese junk and going with the Curtis Albright SW200? Watch out also for Curtis Albright Chinese knock-offs. While my MZJ400 has worked well, like ThreeCW said, they can be hit or miss.

[JCBAS]

Not Chinese junk. Bought one through a sponsor of this website and another bought through a different US vendor. And I will buy the next on through the same site sponsor, i'm just looking for some suggestions on any error on my part that could have caused two solenoids to fail.