RXV not doing the "twist" test

[dgoede]

no, not yet, i may need to bring the cart into a shop and have them check over the controller to diagnose properly. i have gone over the diagnostics from ezgo and don't see any resistance or voltage issues except for the .5v at the brake harness.

[dgoede]

here is an interesting observation. the brk+ (white) at the brake has 48v when taken to ground. but only .5 v when connected to the white/black.

[dgoede]

it appears the brake issue is related to a bad ground on pin 2 of the run plug. the wire diagram shows a connection direct to b-, i don't see that light a gauge wire directly connected to battery ground, will need to trace that wire and see how it actually terminates. Any idea if there is a ground strip besides B- that might be used to terminate the grounds?

[BobBoyce]

Originally Posted by dgoede

it appears the brake issue is related to a bad ground on pin 2 of the run plug. the wire diagram shows a connection direct to b-, i don't see that light a gauge wire directly connected to battery ground, will need to trace that wire and see how it actually terminates. Any idea if there is a ground strip besides B- that might be used to terminate the grounds?

It does not go to ground directly, that black wire from the run plug socket goes to the controller EMB (Electric Motor Brake) output terminal, pin 2 of the 23 pin Danaher connector. The Electric Motor Brake is not given full 48 volts like you would think. It PWMs the negative side hardest at pull-in, then reduces pulse width to a lower average current to keep it held in. That reduces heating in the motor brake coil, extending its life. Sometimes that motor brake output FET goes bad (I have replaced them before), but usually it's something else.

More than likely, you have another issue, such as a HPD (High Pedal Disable) error, preventing the controller from making it to the motor/brake twist test. Where are you located? There may be someone on this forum near to you that has an RXV handset. A read of the error logs and the time they occured would be your best bet. Your local dealer may or may not have the RXV handset. They are only used for the earlier RXV and are pretty expensive, so not a lot of dealers will spend the money. RXVs are an AC drive cart, and dealers may not want to spend the money on tools and equipment that will only be used on that single model. The later RXVs use a Danaher controller, which the handset for that works on other newer carts.

[dgoede]

thanks for that!, This explains why i see minimal voltage (high resistance ground) on that black wire. I confirmed continuity from the black on the run plug to pin 2. So if I understand correctly, if the cart gets a brake pedal error, it won't ground the parking brake or run the twist test?

[dgoede]

Not sure if it may be related, but didn't see any clear diagrams. Hoping someone can confirm. Does the red from the bi-metal switch and the black from pin 18 of the 23-pin connector terminate at the 2 small posts on the solenoid? thanks for all your help.

[BobBoyce]

If you search my prior posts, you should find several posts with RXV wiring diagrams. +48 Volt flows through the bi-metallic switch (overheat shutdown switch) to the + side of the solenoid. Negative of the solenoud is a PWM output (Main Coil) from the controller at pin 18 that initially provides a 36 volt output to pull it in, then tapers it back to about 24 to 18 volts hold-in voltage. Again, like the motor brake, the intent is to reduce heating by lowering current passing through coils that are kept engaged long term.

I'm not a big fan of the Danaher controllers. While they work, several test functions are combined into each test, resulting in more difficulty diagnosing issues from the error codes. Anyone that works on RXVs enough gets intimately familiar with the more common issues, but those new to RXV troubleshooting get frustrated pretty easy. The Curtis controller has more pins and seperates functions to test better. One of the reasons I posted Danaher to Curtis conversion information. I'm a Curtis guy anyways, having closed my EV design business at the end of 2016.

Early RXVs tended to have wiring harness issues. Another thing to look for is both throttle and brake pedal assemblies have a tendency to get particles in the mechanism that makes them harder to move and less likely to return all the way to zero position. The RXV reads this as a high pedal at powerup test and halts testing with the most common HPD error. The best thing you can do is remove the floor mat and the plastic pedal assembly cover, then thoroughly clean both pedal assemblies, their pivot points, and the return springs. When it comes to HPD error, that is the most common cause. I remove the pedal assemblies to do the most thorough cleaning that I can. If the return spring has slop in it, I bush the ends with short pieces of tubing over the spring ends. It's less expensive than changing out the pedal assembly.

Bob

[dgoede]

Thanks Bob, I think my Solenoid question is answered. my concern was if there was a polarity difference between the 2 smaller posts, i don't think there is as it seems to work either way. i am looking now into the pedal issues. It appears that there is no issue with the position sensors showing Normal open on the throttle and normal closed on the brake. I assume voltage testing on the rotary switches is probably key as that would identify the specific position of the pedal to the controller. Are those rotary sensors prone to failure in your experience?

[BobBoyce]

Originally Posted by dgoede

Thanks Bob, I think my Solenoid question is answered. my concern was if there was a polarity difference between the 2 smaller posts, i don't think there is as it seems to work either way. i am looking now into the pedal issues. It appears that there is no issue with the position sensors showing Normal open on the throttle and normal closed on the brake. I assume voltage testing on the rotary switches is probably key as that would identify the specific position of the pedal to the controller. Are those rotary sensors prone to failure in your experience?

The throttle switch is a zero position detect, while the brake switch is set to go open at about 60% pedal travel to remove power from the motor brake and lock up the motor for an emergency stop. It'll likely grenade the brake, but E-Z-GO doesn't care.

The throttle and brake encoders are not potentiometers, they send digital outputs to the controller. Zero on the pedal is not zero on the encoders, they are biased a bit above zero by mounting position. They are pretty reliable, until someone pokes around with a digital voltmeter and fries the 5V logic circuits by crossing a +48V pin with the adjacent 5V pin at the SOC meter when attempting to figure out how to wire in a digital voltage meter in the dash. It happens fairly often is why I mention it.

[dgoede]

the 5v circuits to the pedals looks ok. i see the nominal voltage to the encoders with the pedals up (.33v). before i give up and bring it in for service, i re-did the tests from the Danaher guide. i notice a 1.7v drop on the solenoid with the key switched on. the guide mentions that if there is more than a 1v drop, the controller has disconnected the solenoid. any ideas why it would do that? still no brake release or twist test on startup.