Small 'pop' near controller. Alltrax error 1 Green, 6 Red

[mattadata]

Hi all - I need a little help troubleshooting my EZGO TXT48. I have an Alltrax XCT48500 controller. Everything has been working great, until yesterday. I was backing it out of the garage and heard a loud 'pop' from under the seat. I quickly turned off the key switch and flipped the run/tow switch to tow.

I have inspected all wiring and don't see any issues. All connections seem to be tight. No burnt wires. I didn't smell anything burning, but my wife did.

The controller is flashing a code of 1 green and 6 red lights. From the Alltrax manual this code is: Pre-charge Failure:
B+ voltage and KSI voltage differ by more than 5v. Stuck solenoid.

Following ScottyB's Diagnostic guide http://www.buggiesgonewild.com/elect...gnostics.html: I have 51.6 V at the pack.
I have 51.1 V at the solenoids large post on battery side.
I have 100 mV on the solenoid's other large post.

Since the 3rd reading is more than 3 volts less than pack voltage, the guide says the resistor is faulty. But the Alltrax error code says the solenoid is stuck.

I need some help on what to test next to isolate the problem. Thanks!

[ewiggins7299]

Test the resistor. Pull it off and see if the ohms reading is close to that of the resistor rating.

[JohnnieB]

Im' not a 100% sure of this, but from what I can deduce from the schematic, the filter capacitors in a XCTxxxxxTXT48 are pre-charged via Pin-9, rather than having a pre-charge resistor between the large terminals on the solenoid. (There is a diode between them for EZGO carts, but that is there for a different reason.)

When the Run/Tow is in Run, B+ is applied to Pin-9 and the filter capacitors should charge to a bit less than pack voltage. When the keyswitch is on, there should be battery pack voltage on Pin-10. If the pre-charge voltage on the capacitors (Measured at the B+ terminal on the controller) differs more than 5V from the voltage on Pin-10, you get the Pre-charge failure error.

Since you are only getting 100mV on the controller's B+ terminal before the solenoid contacts close, it is a valid error.

First, verify you are getting Battery pack voltage on Pin-9 when Run/Tow is in Run.

If you don't, disconnect J-1 and measure the voltage on Pin-9 while it is disconnected. If you now have pack voltage, your XCT has very likely failed.

Call Alltrax, they may have some other tests they'll want you to do.

Hopefully it is still under warranty. (The loud pop doesn't sound encouraging)

[JohnnieB]

Originally Posted by ewiggins7299

Test the resistor. Pull it off and see if the ohms reading is close to that of the resistor rating.

The XCT has an internal pre-charge resistor and does not use/need a separate one on the solenoid.

See Note-4 on schematic posted above.

[mattadata]

Thanks. I disconnected J-1 and measured the voltage between pack negative and PIN 9 on the wiring harness. I got 51.5V, which is my pack voltage. I guess time to call Alltrax.

[JohnnieB]

Yes, it sounds like it is time to call Alltrax.

Just curious, what does Pin-9 measure when it is plugged in?

[mattadata]

I didn't make that measurement. How do I measure when J-1 is plugged it? Do I push the probe tip through the insulation?

[JohnnieB]

I've never seen the plug EZGO uses for the J1 connector. If they used what they have been using for other models, it is a Molex plug and the backside is open.

It is a 16 pin plug, so the wires may be closer together and less space for the test probe, so use a short piece of 18Ga solid to stick in the connector and measure off the other end of it.

[mattadata]

51.6 V when J-1 is connected.

[JohnnieB]

I'm only speculating about the XCT's internal connections, but if I am correct, there is an open between Pin-9 and the filter capacitors, or between the filter capacitors and the B+ terminal.

Please let us know what Alltrax says.