36V series losing speed - at wits end! SR48500 installed

papabearsc

2004 Ezgo 36V series cart. 1 year old batteries still test good.

Bought cart a year ago with a bad FR switch and replaced it with a "heavy duty" eBay unit (yeah I'm smart like that) to get it running. Fast forward to a month or so ago. Installed SR48500 and solenoid from ScottyB and new 2AWG wires. Cart was a beast! Top speed increased to about 14-15mph from the 12-13 stock (didn't expect too much anyway). My plan was to eventually go to a Plum Quick Cobra motor and run it 36V and eventually run it 48 when I upgrade batteries next time (maybe sooner than later).

Cart has been used a little bit in the last month, mainly tooling around the neighborhood, but has steadily felt like it was losing speed. I decided to start monitoring, and I now cannot reach over 11 MPH on flat road....so diagnosing I went.

Put cart on jack stands, hooked up the computer and I'm only getting 72% throttle at full pedal - so off to ITS settings I go. I had an excessive (more than 17/64) gap at the rod. Tested voltage and instead of 10 at top and 6 at bottom of pedal I had 6.5 and 4 respectively. I adjusted the rod to where I had proper gap and full throw through the inductive sensor. I re tested and had same voltage readings as before, and throttle % is still stuck at 72%. Checked voltage at controller pins and at sensor and they read the same.

Changed speed knob setting to regular in toolkit and no change.

Also noticed some bearing noises in motor while doing this - Cobra motor coming sooner than later.

My questions:

Would a bad ITS sensor limit throttle % to alltrax?
Would a failing FR switch lead to slowly limited amp flow reducing speed gradually? Or would it fail spectacularly and just quit?

Thanks for the help - hope I've answered most of your questions already, but I'm plenty capable of following direction to test.

Thanks

BGW

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yurtle

If you have a four wire Molex plug on the cable from the throttle box to wiring harness, usually located between controller and FNR, eliminate it, and butt-splice or solder then seal with quality heat shrink.

This has two ITS wires and a bad connection can cause throttle problems.

Attached Images

Molex.jpeg (254.5 KB, 0 views)

papabearsc

This was eliminated when I installed the controller and associated parts.

yurtle

Anything is possible.

I doubt if an FNR could dissipate enough amps (it can't "limit" amps) in the form of heat without melting down, but you can take it for a ride and then check each and every cable connection for heat. I use a spit licked finger, but a temp gun is safer.

Do you charge your batteries after EVERY trip? Can you check pack voltage while driving, to see if it drops excessively, it probably will. If it does, check each battery while driving to see if you have one bad battery. Also check electrolyte levels.

yurtle

You mentioned "bearing noise". It may be your motor brushes are wprn out, which is easy to fix. The Repair/Service Manual has detailed instructions for checking them - my 1998 was fine - and you can replace the one bearing in the motor. The other motor bearing is in the rear end, and has just as many miles as the one in the motor, if it's bad. I just replaced my bearing while checking my brushes and cleaning the commutator with a ScothBright.

cgtech

In Alltrax toolkit, in one of the top drop-down menus, select "clear auto-cal". This will reset the controllers automatic calibration of what "full throttle" looks like. It will then re learn based on what the throttle is doing at this time.

papabearsc

Ron from Alltrax helped me with this and it worked!

I still have some bearing noise, but have purchased a motor and will be going in ASAP.

Thanks everyone!

Brob1969

Glad to hear you got it fixed. Let us know how the new motor works out.

papabearsc

With a top speed of 13-14, it's just not cutting it in the neighborhood.

PQ says I can run the Cobra 36V and expect 22-25 mph and then run same motor at 48V when I upgrade batteries next year, but no expected speed numbers at 48V, but I'm sure it'll be good.

Sir Nuke

I did something VERY similar.....up graded to a high speed motor which gave me a top end of 24 to 25 mph at 35v......then when I went from 36v to 48v, it netted me a top end of 29 to 30 mph. although we don't have the same motors, I bet you should net the same or close results.