Run Away Cart on Wide Open Throttle

[ThreeCW]

Run Away Cart on Wide Open Throttle

What Happened:
My wife was going to back our cart out of the garage … Fwd/Rev switch was in neutral … turned on the battery switch … turned on the key switch and without touching the accelerator pedal, the cart immediately lurched backwards under full power / wide open throttle (WOT) even though the cart was in neutral. Thankfully, no person, pet or thing was behind her … she had her wits about her and turned off the key switch and the cart came to a stop.

Cart Description:
1998 Cushman Hawk 48v Utility Cart - Model 797024 (low hour cart – mostly original) with:
Batteries: 8 pieces of 6V US Battery 125 XC2 – 242 amp-hr (2013 vintage)
Battery Switch: Blue Sea model 6006, 48V DC, 300 amp continuous / 500 amp intermittent
Solenoid: Tyco LEV200 Solenoid - 500 amp continuous + 470 ohm resistor + 3 amp 1N5408 diode (new in May 2017)
Controller: Curtis PMC Model 1219-8405, SN 8225-525833, 36-48V, 600 Amp
FR Contactor: Curtis Albright - Type SW202N-228, 48V (250 Amp rating?)
Motor: identified from manual as GE Model 5BC49JB3054 – 6.5 hp – 48V
Pot Box: Curtis PB-6 (2 wire) – 0 to 5000 ohm
Cables: 2 gauge
Tires: 23”
Maximum Speed: 17 mph on gravel driveway (GPS)
Weight: 1620 lb operating weight / 1200 lb capacity

History:
We have owned this cart for approx. 9 months. The cart is used on our small farm – both on gravel roads and in pastures. Slow speed, hilly driving is typical, with and without loads. Typical use is about 1/2 hour per day at 5 to 10 mph. Faster when coasting down hill.

In the past winter, we experienced a few intermittent acceleration problems, where the cart would occasionally run with the accelerator in a stuck position, at about half power to full power without the accelerator being applied. When the “sticking” first occurred, I would turn off the key switch, followed by the battery disconnect switch and the problem would be gone when I powered up again and turned the key switch on. The problem started occurring more frequently and sometimes would not be fixed by turning the key switch off / power down (but the cart would stop with the key off).

In researching BGW articles, I suspected that the solenoid may have been sticking, and attempts to “unstick” the solenoid with gentle taps with a small ball-pean hammer “appeared” to relieve the problem. I removed the original solenoid for bench testing and in the process, I broke off one of the main connection studs (ooops!! – guess I need a new solenoid now). I bench tested the old solenoid (including powering up the coil) and confirmed that it was functional (except the sheared off main post). I disassembled the solenoid completely and the contacts showed evidence of moderate arcing. I installed a replacement solenoid and fitted it with a 470 ohm pre-charge resistor and a 3 amp - 1N5408 contactor coil diode.

The cart was used problem free for 10 hours after the solenoid replacement (call it 50 miles or so) and all was operating normally until the run away / WOT event described above. The night before the run away event, the cart was lightly washed including the undercarriage. After washing, the cart was driven 200 yards and parked in the garage with no problems experienced.

Based on my research of the BGW site (thank you members for your educational posts), I performed the following Trouble Shooting after the Run Away Event:
1) Jacked up rear axle (safety first!)
2) Duplicated Run Away – Occurred immediately in reverse when turning on key switch with the direction switch in any position (forward, neutral and reverse) and accelerator pedal not applied.
3) Removed 24 pin Molex plug from controller. Checked Pot Box resistance at the 24 pin Molex plug with readings every ¼” of pedal travel – smooth increase in resistance from 0.9 ohms with no pedal travel to 4960 ohms at full pedal depression – repeated test with very similar results. Pot Box is functioning OK.
4) Checked Solenoid with key switch off: Input = 51.4 v / Output = built to 46.0 v in 1 minute (powering up through 470 ohm resistor – Solenoid OK in key switch off position)
5) Quickly checked Solenoid with key switch on / direction selector in neutral: Solenoid output = 49.9 v (wheel rotating rapidly backwards) – Solenoid OK in key switch on position
6) Voltage Check with battery switch on, key switch off, FNR switch in neutral, seat switch open (not on seat) with the following voltages recorded:
Solenoid input = 51.4 v (battery pack voltage)
Solenoid output = 46.0 v (reduced voltage due to resistor)
Reverse Contactor Input / Controller B+ = 46.0 v
Reverse Contactor “+” / Forward Contactor “+” / Controller A2 / Motor A2 = 38.26 v
Forward Contactor out / Motor S2 = 46.0 v
Reverse Contactor out / Motor S1 = 46.0 v
Motor A1 / Controller M ”-“ = 38.25 v
Controller B1 = 0 v
(I am not sure how to interpret the 38.25 voltages)
7) Battery Pack Check – 8 batteries = 51.4 v
Bat 1 = 6.47 v, Bat 2 = 6.47 v, Bat 3 = 6.40 v, Bat 4 = 6.48 v
Bat 5 = 6.37 v, Bat 6 = 6.35 v, Bat 7 = 6.40 v, Bat 8 = 6.39 v
8 ) Cable Check – all cables are 2 gauge and checked out good at 0.2 to 0.4 ohms
9) F-N-R Switch – removed and continuity tested OK (lubricated switch)
10) Key Switch – removed and continuity tested OK (lubricated switch)
11) Controller Wiring – all small gauge wiring to controller checked for continuity - all OK
12) FWD / REV Contactor – completely disassembled – contacts were functional with evidence of minor to moderate current arcing.
13) Two (2) days after Run Away / WOT event, function tested cart (with rear axle jacked up) and problem was reduced. Cart would not run away when in neutral but still WOT on Fwd or Rev switch setting.
14) Three (3) days after Run Away / WOT event, function tested cart (with rear axle jacked up) and problems were further reduced. Cart would only moderately run away in Fwd or Rev – no longer at full throttle.
15) Four (4) days after Run Away / WOT even, function tested cart (with rear axle jacked up). No apparent problems were present. Removed cart from safety stands and performed road test. Generally normal cart operation with some minor Run Away events (like a sticky throttle event) that would go away with direction switch in Neutral.
16) Continued to use the cart over the next 4 days and all problems diminished and eventually went away.
17) Since then, we have used the cart for about 6 hours over the past 20 days and have experienced NO FURTHER PROBLEMS.

Controller Review:
Curtis PMC Model 1219-8405, SN 8225-525833, 36-48V, 600 Amp
Controller Inputs as follows (10 wires into Molex 24 pin connector):
Pin 1 – Key Switch
Pin 2 – Seat Switch
Pin 3 – Direction Switch – Mode Select (same switch point as FWD on pin 10)
Pin 10 – Direction Switch – FWD
Pin 11 – Direction Switch – REV
Pin 14 – Pot Box Low
Pin 16 – Pot Box 5K-ohm (I have a 2 wire pot box)
Pin 17 – Main Contactor / Solenoid driver output
Pin 18 – Forward Contactor driver output
Pin 19 – Reverse Contactor driver output

All 10 wires going into the 24 pin Molex connector were successfully continuity tested.

Note – When I bought this cart, the previous owner also gave me a cover plate that had fallen off of the cart … he was not sure where is was from … it turned out to be end plate from the Curtis controller! When I bought the cart, it operated normally with no apparent problems. Shortly after purchasing the cart, I removed the Curtis controller from the cart and although no moisture or debris was present, I left it over a hot air heating duct overnight (it was winter in Canada) to remove unseen moisture (if any). I then mixed up some two part epoxy glue and glued the cover of the Curtis controller back in place. No problems were experienced with the cart for the first month or so after gluing the controller cover plate back in place.

My Analysis:
I believe that our Run Away / WOT event was due to water creating a short somewhere in the cart wiring. My guess would be most likely water in the Molex plug of the controller or water entry into the controller itself. I base this on the “light washing” the cart received the night before the WOT event and how the problem slowly fixed itself with time (and likely evaporation of the offending water).

My Go Forward Plan:
1) Eliminate all washing of the cart around the electrical controls
2) Remove the controller and apply silicon caulking to seal potential leak points into the controller and into the Molex connector
3) Eventually replace the controller – not that easy as I have not been able to find a replacement plug and play controller – I may have to get FSIP to rebuild my controller.

BGW Members
- Any comment on my logic above?
- Am I missing anything obvious?
- Does anyone know of any plug and play controller options for my 10 wire input style of controller (I already spoke with Alltrax and they do not have anything compatible)

Thank you for your feedback.

Regards, 3CW

[Alex Faught]

Seems you are on the right path, definitely sounds like it is a water issue. Hope you get it worked out, I think you are the only other cushman hawk/utv owner here.

[Mooncarter]

Could you explain in a little more detail? Also, how wet was the water?

Also, since you have not had any problems for 20 days of use, It will require an expert to diagnose the problems you are not having.

[ThreeCW]

Originally Posted by Mooncarter

Could you explain in a little more detail? Also, how wet was the water?

I think you forgot to include a .
The water was pretty wet, until it evaporated, then became dry .
I guess I could of just posted "my cart is not working, HELP".
Sorry about the lengthy post, but I wanted to post my trouble shooting steps taken, which might help someone else having a similar problem.
Or might help me to resolve my problem / come up with a good replacement option for my controller.

[Mooncarter]

LOL. Just joking around. I think you will be fine now. I have had water create temporary quirks too.

[kgsc]

You have a 0-5K pot box so it is possible you had some water making a ghost connection across those leads. That being said Curtis normally has high pedal disable setting that senses if the pedal is depressed at key on and will normally throw an error code. Yours may have that turned off and hence will run away. A hand held programmer would tell you what it is set to and possibly change the setting if it is turned off..

Manual is here http://www.fsip.biz/Documents/1214.pdf Page 26 shows HPD settings

[ThreeCW]

Originally Posted by kgsc

Curtis normally has high pedal disable setting that senses if the pedal is depressed at key on and will normally throw an error code. Yours may have that turned off and hence will run away. A hand held programmer would tell you what it is set to and possibly change the setting if it is turned off.

kgsc,
Thank you for your suggestion regarding High Pedal Disable (HPD) ... I hope to find someone locally who can read the error codes internally on my controller and ensure that the HPD is either set for type 1 (KSI / Seat Switch input before throttle input) or type 2 (KSI input before throttle input). I would guess that if it was set correctly to one of these two disable options and that it did not disable the cart, then that would indicate a controller error / failure. Good suggestion to check this. Thanks.

I forgot to mention that the controller LED light was NOT throwing any error codes when I was troubleshooting this WOT problem.

Regards, 3CW

[kgsc]

Just occurred to me you can test this setting. While you are in the cart with key off, press the go pedal then turn the key on. If the cart takes off, HPD is not enabled.

[ThreeCW]

Originally Posted by kgsc

Just occurred to me you can test this setting. While you are in the cart with key off, press the go pedal then turn the key on. If the cart takes off, HPD is not enabled.

Thanks kgsc!

I was able to successfully test the High Pedal Disable (HPD) setting as you suggested. Seated in my cart (seat switch closed) and with the accelerator pedal applied at greater than 1/4, when I turn the key switch, the solenoid would close as normal but when I activated the Fwd/Rev Switch, the FR Contactor would NOT engage ... and the cart was disabled (with a high pedal ... i.e. over 1/4 trottle).

I also tested at below 1/4 throttle and the HPD would NOT disable the system. As per the Curtis Controller 1219-8 manual, this is the correct operation of the controller HPD function for a throttle demand less than 25%.

Good to know that the HPD function of the controller is working properly ... not sure if it was though when we experienced the Run Away / WOT event.

So I am still lead to believe that our problems were as of result of water creating a short somewhere in the cart wiring or in the controller itself.

Since the cart is now operating normally again (it appears that the offending water has evaporated), my next step will be to remove the controller, see if there are any cracks in the epoxy repair job of the controller cover and apply silicon caulking to seal potential leak points into the controller and into the Molex connector.

A future step will be to source a potential replacement for the 1998 version Curtis PMC Model 1219-8405, SN 8225-525833, 36-48V, 600 Amp Controller with 10 wire inputs / outputs from the Molex 24 pin connector. We really love having this cart here on the ranch (we are easily pleased) but want to ensure that it is safe and reliable for future use. Hence the thought on replacing the controller. I previously contacted Alltrax and they do not have anything compatible. I may have to get FSIP to rebuild my controller but my preference is to purchase a new one if possible. Any guidance on this would be appreciated.

Also on the wish list is replacing the batteries with a lithium pack sometime in the future (current batteries are 4 years old and working well enough). It would be nice to lighten up the cart but more importantly, get rid of the battery gassing concerns when charging (especially in winter when charging is usually done in a heated garage).

Thanks for any help you can offer in guiding me through this problem.

Regards, 3CW

[kgsc]

3CW, What you have is a sepex setup. When you get ready to replace the controller it will take a little bit of wiring but there are many options out there to replace it with. The controller you currently have has the feature of being able to have 2 different modes of driving changeable on the fly. It is probably not being used but its there

We built a cart a few years ago with a curtis 1268 500 amp with this feature so it allowed us a dirt mode and a street mode. It allows you to have different speed limitations as well as regen and current control based on which mode it was in. Our is setup for lower speed but more torque in Low(17mph) and less torque but more speed in high(26mph) with shifting on the fly..