2009 YDRE speed dropped to 15mph & it soon died

Discussion in 'Yamaha Electric' started by patbbb, Aug 23, 2018.

  1. patbbb

    patbbb New Member

    My 2009 Yamaha YDRE dropped to 15 MPH then died. I cleaned corroded throttle stop switch, tightened all bat, solenoid & controller connections. Cart ran again, but only 15mph- normal speed is 19.9 - 22. Cart then would not run again. Throttle position sensor resistances tested out of spec and I have part ordered. Don't have special cable needed to test the motor speed sensor voltages so I pulled the sensor. It looks absolutely clean and the magnet also looks good. Any suggestions for finding the problem while I'm awaiting the TPS in case the TPS doesn't do it?
     
  2. HotRodCarts

    HotRodCarts Cartaholic

    If the throttle positioning sensor tested out of spec I would say the new TPS should solve the problem. Let us know how it runs after changing the TPS.
     
  3. patbbb

    patbbb New Member

    Sorry to say (2) replacement sensors did not fix the problem. After knocking my head against the wall several times I called in the local service tech guru who tells me he's never replaced a throttle sensor in many, many years. After testing the motor, disassembling & cleaning the armature and brushes, he concludes there has to be a short in the controller. But the only way to confirm that would be replacing it at a hefty price and, of course, that electronic part wouldn't be returnable if it didn't fix the cart. So could 2 stuck brushes and a dirty armature have shorted the controller? Also can that be tested?


    OR (& what bugs me) is according to my Yamaha Repair Manual, ohm readings on 2 terminals (blue-black) of the sensor should be 5k- I get 2k, then it immediately jumps to 25k. On the other side (orange-black) is supposed to be 0-150 and increase to 5k with accelerator fully depressed. I get 34k steady and no change. (Resistance between the blue & red terminals is 325 ohms both ways). It's the same on the original sensor and the 2 new after market, non-branded, replacements. I've tried reversing the +/- leads for the diode which I assume is in the circuit. Well, I'd think even if sensor is off spec it should show a change as the pedal is depressed, which makes me reluctant to buy a controller.


    Your further input would be greatly appreciated.
     
  4. HotRodCarts

    HotRodCarts Cartaholic

    Where are you getting the new speed sensors? Did you tell the Yamaha "tech guru" the speed sensors tested out of spec? What did he say about that?
     
  5. patbbb

    patbbb New Member

    Thanks for the fast reply! They are "Huskey Parts" from an Ebay vendor at substantially lower price than local dealers. The technician, who has an excellent reputation- the reason I called him- says he has never replaced a speed sensor in over 25 years of fixing carts and they just don't fail. Besides the original speed sensor and the 2 new replacements, he connected a supposedly good used one that he had on the truck with also no change. FYI- I was getting different, but still very high resistance, on 2 DVOMs. So I tried my analog VOM which also showed different, but far out readings. Could this have blown the diode or other electronic component within the sensor, resulting in them all testing bad? Also, I didn't measure resistance on the used sensor from the truck & all meter tests were done with the system powered down in tow mode or with the sensor on the bench. I've ordered a new DVOM to compare readings with the old ones- should arrive over the weekend.

    So, any thoughts or tests you can suggest besides biting the bullet and buying a more expensive speed sensor? Although I agree the motor needed the work done, I don't want to put a costly controller into a 2009 cart which also will be needing batteries ($$$) in a year or so. If I can get it running, the trade or resale value will increase considerably.
     
  6. HotRodCarts

    HotRodCarts Cartaholic

    Have you checked the small and large terminals on the solenoid to see it's getting power and activating? Does the solenoid click when you press the throttle with the key on?
     
  7. patbbb

    patbbb New Member

    I inadvertently said speed sensor in my last post when I meant throttle (position) sensor- the one that's testing bad-sorry. Yes, the solenoid activates and clicks when the throttle is pressed. I also have a new speed sensor available- the one that mounts on the end of the motor with 4 screws. I pulled the old one but didn't change it because it looked like new. So my same (last) question remains: "any thoughts or tests you can suggest besides biting the bullet and buying a more expensive throttle position sensor?"
     
  8. HotRodCarts

    HotRodCarts Cartaholic

    I'd check to see it you have full battery pack voltage on both large posts of the solenoid when it clicks.
     
  9. patbbb

    patbbb New Member

    Will have time to check solenoid voltage tomorrow & get back to you. Assuming it tests good, is there a chance I damaged the diode or other electronic component within the throttle sensor. I don't know what kind of diode is in it. As I said earlier, all tests were done without power to the circuits, other than voltage tests. Lastly, if I put a jumper on the TPS connector at the accelerator and momentarily turn the key on (rear wheels jacked up), do I risk damaging the controller or other electronics since that would be wide open throttle?
     
  10. patbbb

    patbbb New Member

    Solenoid tests:
    Battery side reads 50+ volts.
    Controller side starts low, around 10v and slowly creeps (0.1v at a time) to 48v & continues its rise very slowly.
    Readings are the same with key on or off. FYI I bypassed the throttle stop switch with a jumper wire- temporarily for testing because that tiny ball in it went flying to oblivion when I disassembled to clean it. Therefore the solenoid clicks repeatedly as it is always energized.
    Also there is continuity- 0 ohms- across the large posts. Resistance across the primary, small terminals, is 130 ohms, although my manual indicates it should be 21 ohms.
    So, are the voltage readings indicative of a bad solenoid &/or the controller in addition to a possible bad TPS?
     
  11. patbbb

    patbbb New Member

    I just rechecked solenoid voltages after taking the controller out of the circuit, thinking it may have affected readings. Voltage didn't register I assume because there was not a ground. BUT, after reconnecting controller & using a better ground at the battery pack instead of the motor, voltage on the battery side was again 50+ and a steady 39 volts on the controller side. Hope that helps.
     
  12. patbbb

    patbbb New Member

    Cart is not running & I sill need HELP! Anxiously await your diagnosis/thoughts after all the tests and would greatly appreciate additional feedback from you. Would like to just get this cart running! So far everything I've looked at tested bad: the throttle stop switch, TPS, motor brushes and solenoid voltage. It just doesn't male sense to me.
     
  13. patbbb

    patbbb New Member

    Neglected to mention that I tried jumping the large solenoid terminals because of the lower reading on the controller side. Resulted in no change.
     

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