99' EZGO TXT DCS 36v stuttering action

[pchilson]

Hi,

From the metal serial number tag in the cart:
G299
1188571

From the serial number lookup:
Make: TXT
Powertrain: Electric 36 V
Sub Model: TXT Standard (DCS)
Year: 1999

Power Wise charger
Industrial Model: 28115 G04
Serial: 90670

We use the cart only for golfing. The course is in the Ozarks and is moderately hilly. Typical use would be one to three rounds of 18 holes when used. Cart is kept in a cart shed at the course and plugged in after any use.


We bought this cart in December of '18. The Trojan T-105s indicated about 4 1/2 years old at that time. We purchased the cart at a low price knowing we would need to replace the batteries before long.

We used the cart until early August this year without problem. Then one outing it suffered a battery cable failure which melted the post on one of the batteries resulting in the need to replace the batteries.

We had them replaced in early August '19 with new Trojan T-105s. At that time all battery cables were replaced with new 4 ga cables and new ends were put on the wiring from the harness to the batteries. All was good again for 4 or 5 uses of the cart until last week when on one outing I was on hole 13 (a long but moderate uphill climb) near the top of the hill the cart just seemed to loose power for a moment then came back resulting in the "stuttering" action. I thought "crap" and coaxed the cart to an out of line of fire location thinking I would need to tow the cart back in. Well this is the furthest point from the club house so we got out, finished the hole (3 to 4 minutes tops) and upon getting back in the cart it took off and went the rest of the holes without doing this again (worked fine). Four days later it did the same thing again but on hole 8 this time (a shorter but steeper hill).

I started google searching on "ezgo txt dcs 36v stuttering" and came upon a small number of threads on here as matches. Not a lot of info and none of the thread starters ever capped the threads with their final findings, so here I am.
Lots of the diagnoses were about batteries (bad cell, bad battery) and so forth. Some good info on how to check for this. I followed the suggestions and tested voltages with my meter.

Pack voltage after charge: 38.4 at rest, fluctuating to no lower than 35.9 under load but generally in the 37v range while driving.

Individual battery readings at rest: 6.7v plus or minus .2 At load I can't remember the readings but were in range of what they should be with no "oddball" readings on any individual battery.

I started to suspect a heat related cause as this seems to happen only after climbing (heavy load). Yesterday I hooked the meter to the pack voltage and ran the cart up and down one of the steeper inclines to try to get the stuttering to happen while being able to see what the voltages were doing. After climbing the hill for the 3rd time it started stuttering. Pack voltage did not show anything "odd" compared to when it wasn't "stuttering" but one thing I did notice was it seemed to "tik-tok" from 37.2 to 36.6 and back, (tik-tok, tik-tok).

Someone suggested slipping splines on the axle but I would think this would be more of a "jerking" sensation. You can definitely feel the power loss and restore (like a light switch turned off and on) as opposed to a jerking/slipping sensation.

I have cleaned and tightened as many connections as I can get at including the 4 motor connections. There are more switches that can't be accessed easily that haven't been checked.

I'm not sure where any of these symptoms lead me to look. We are ok with spending some money on the cart as we are quite above water even after new batteries but I also don't want to shotgun parts to find a fix.

We only use the cart for golfing. I don't need it to go faster, jump higher or look better than anyone else's, just want it to complete the rounds and get us back to the cart shed.

Any help or direction is appreciated. Thank you.

[Kenski77]

Just had the same problem on a series. I thought if was the throttle coil. Here it was the connector that went from the pedal box to the controller. There was a loose wire in the plug. It took awhile to find it as I didn't think of it and I have 20 years of electrical/electronics maintenance. I finally checked it and bingo, I wiggled the wire and was able to reproduce the lost voltage.

[JohnnieB]

The DCS was EZGO's first attempt at producing a SepEx (SEParately EXcited) drive system and was replaced by the PDS in about 5 years due to the high failure rate of the controller (Curtis 1206SX), which has no under voltage protection. Sounds like your DCS controller is getting ready to give up the ghost.

Replace the stock controller with an Alltrax XCT48300-DCS (or XCT48400-DCS if tires are taller than 18" in height or cart has rear seat) and take motor to local electric motor shop and have it serviced. (After 20 years, it needs brushes, bearing and cleaning)

The XCT will very likely speed the cart up some, but the vehicle you drove to the golf course most likely can exceed the speed limit on the streets you take to get to the golf course and you probably manage to avoid speeding tickets.

Also, the XCT is user programmable and can be toned down.

[pchilson]

Originally Posted by Kenski77

Just had the same problem on a series. I thought if was the throttle coil. Here it was the connector that went from the pedal box to the controller. There was a loose wire in the plug. It took awhile to find it as I didn't think of it and I have 20 years of electrical/electronics maintenance. I finally checked it and bingo, I wiggled the wire and was able to reproduce the lost voltage.

Thank you for this. I can only hope it is a simple wire connection issue.
I am on my way down there and will give this a look see.

[pchilson]

Originally Posted by JohnnieB

The DCS was EZGO's first attempt at producing a SepEx (SEParately EXcited) drive system and was replaced by the PDS in about 5 years due to the high failure rate of the controller (Curtis 1206SX), which has no under voltage protection. Sounds like your DCS controller is getting ready to give up the ghost.

Replace the stock controller with an Alltrax XCT48300-DCS (or XCT48400-DCS if tires are taller than 18" in height or cart has rear seat) and take motor to local electric motor shop and have it serviced. (After 20 years, it needs brushes, bearing and cleaning)

The XCT will very likely speed the cart up some, but the vehicle you drove to the golf course most likely can exceed the speed limit on the streets you take to get to the golf course and you probably manage to avoid speeding tickets.

Also, the XCT is user programmable and can be toned down.

I see that you are a respected member/expert on these carts. I appreciate your input on this issue.

I would like to ask, are you suggesting a controller replacement because you have seen this specific problem and the controller was responsible and I should just replace and be done or is this a "most likely" cause but might not be the problem?

Thank you. I appreciate the input guys!

[JohnnieB]

Originally Posted by pchilson

I see that you are a respected member/expert on these carts. I appreciate your input on this issue.

I would like to ask, are you suggesting a controller replacement because you have seen this specific problem and the controller was responsible and I should just replace and be done or is this a "most likely" cause but might not be the problem?

Thank you. I appreciate the input guys!

The intermittent part of intermittent stuttering more or less eliminates everything except battery, motor and controller. Your battery voltages at-rest and under-load look good, so it's down to motor or controller, or both.

As I mentioned, the stock DCS controller is a high failure item and was very likely subjected to low voltage conditions prior to the battery replacement, so it is the most likely suspect.

Unless the motor has been serviced at some point in its 20 years of service, it most likely needs some TLC.

--------------
Are there other possibilities? Yes.

As Kenski77 mentioned, there is a in-line connector in the gray cable from the pedal box under the floormat, to the cart's wiring harness that causes all sorts of strange symptoms, but your cart's stuttering appears to be heat related (heavy loading - hills). Best thing to do is eliminate the 4-pin in-line connector with individual wire splices (crimped butt splice or solder joints) covered with marine grade (waterproof) shrink tubing.

Also, there might be a bad high current cable or connection. Excessive resistance in the amp delivery circuit will reduce the voltage at the controller and if it is severe enough it may cause stuttering. Are any of the 10 thick cables or their connections getting hot? Ideally, none should get more than 10°F above ambient. (If 20 year old OEM 6Ga cables are still in use, they ought to be replaced with 4Ga or thicker cables for more efficient operation.)

Measure the voltage between the controller's B- and B+ terminals under load and if the voltage is much less than the battery pack voltage under the same load (going up same hill), then the cables need some TLC.

Bottom line is that, with a little catching up with the normal maintenance that should have been done over the years, you've got a great cart for a hilly golf course.

[pchilson]

I will cap this thread.

Never did find the cause of the stuttering action.

We decided to trade this cart in on a new '19 gas model ez-go, so end of story.

Apologies to anyone else that is also trying to find what causes this problem without just throwing cash at it. I wish you luck.