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Auto WLtoys 12428 Steering Issue: Replacing CF 502 Potentiometer, Car Turns One Way Only

yarkk 14847 13
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  • #1 16697932
    yarkk
    Level 12  
    Posts: 53
    Rate: 7
    Hello,
    some time ago my son broke the steering wheel for this model. After unscrewing the remote control, it turned out that you need to modify the element responsible for twisting. The potentiometer marked CF 502 was originally mounted, as in the pictures below:
    Auto WLtoys 12428 Steering Issue: Replacing CF 502 Potentiometer, Car Turns One Way Only Auto WLtoys 12428 Steering Issue: Replacing CF 502 Potentiometer, Car Turns One Way Only
    The potentiometer could not be connected to the control element (steering wheel), so I decided to replace it with others. In the electronics store, a 5 k? potentiometer was chosen, exactly like here:
    Auto WLtoys 12428 Steering Issue: Replacing CF 502 Potentiometer, Car Turns One Way Only
    After connecting for a few minutes, the twist worked like new, then getting weaker. After charging the car battery, it turned out that the car turns only one way, the other as if it was blocking something. We manage halfway in such a way that I switch to the regulation which is responsible for setting the wheels for straight travel, so that it turns equally left and right, but this is at the expense of the turning radius.

    What is wrong ? How to fix it ?
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    #2 16698217
    1 PAWEL
    Level 42  
    Posts: 7210
    Help: 674
    Rate: 1362
    CF 502 potentiometer with 5 k? linear potentiometer, but with a working range of, for example, 110 degrees, 45-240 degrees, depending on the manufacturer, there must be a potentiometer from modeling apparatus.

    Auto WLtoys 12428 Steering Issue: Replacing CF 502 Potentiometer, Car Turns One Way Only Auto WLtoys 12428 Steering Issue: Replacing CF 502 Potentiometer, Car Turns One Way Only
    Auto WLtoys 12428 Steering Issue: Replacing CF 502 Potentiometer, Car Turns One Way Only
    After the embankment you can see the scope of the field of activity.
    -----------
    to check.
    Fixed position "0" on the potentiometer not set.
    And the servo incorrectly positioned lever point "0".


    .
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  • #3 16698359
    yarkk
    Level 12  
    Posts: 53
    Rate: 7
    That would match, it looked original.
    Auto WLtoys 12428 Steering Issue: Replacing CF 502 Potentiometer, Car Turns One Way Only

    What should the replacement be then? Alternatively, where to buy?
    I visited three electronics stores and one model shop and they didn't have anything like the original.

    Quote:
    Fixed position "0" on the potentiometer not set.
    And the servo incorrectly positioned lever point "0".


    I understand that after installing the appropriate potentiometer will be set to "0" on the potentiometer, i.e.
    Auto WLtoys 12428 Steering Issue: Replacing CF 502 Potentiometer, Car Turns One Way Only

    and possibly (although there was nothing buried here) servos in the model.
    Yes ?
  • #4 16698492
    1 PAWEL
    Level 42  
    Posts: 7210
    Help: 674
    Rate: 1362
    The zero on the potentiometer is factory set in the form of a projection acting as the basis for its arrangement in the apparatus. And the cut needed to maintain the position of the steering wheel or throttle lever.
    When you turn on the model and apparatus, the servo should assume the zero position, then the lever position should be set. To get the same steering angle and to adjust the length of the pull rod so that the wheels are set for straight travel, all that is left is to slightly adjust the trimmer.
    On the pattern that fell, you would have to search ebay or translate from another,
    or buying similar dimensions and axis for adaptation.
    I stock up on AliExpress - CF B502 potentiometer.
    Or - B5K 5K Linear Taper Potentiometer for RC Transmitter Control 120 Degree Rotation

    Auto WLtoys 12428 Steering Issue: Replacing CF 502 Potentiometer, Car Turns One Way Only

    But first you need to set the range of the potentiometer in degrees.

    link

    yarkk wrote:
    it looked original.

    Careless soldering of the short circuit.

    .
  • #5 16701705
    yarkk
    Level 12  
    Posts: 53
    Rate: 7
    1 PAWEL wrote:
    But first you need to set the range of the potentiometer in degrees.

    The working range of the steering wheel is limited as shown in the figure below, i.e. 40 ° to the left and 40 ° to the right.
    Auto WLtoys 12428 Steering Issue: Replacing CF 502 Potentiometer, Car Turns One Way Only
    If the range of the potentiometer is those silver lines on the potentiometer, it goes out on the left and right together about 180 °, but it is difficult to accurately measure.

    What should the potentiometer be like?
    I didn't buy anything on ebay or aliexpress. There is nothing in PL?
    Alternatively, I can transfer the indicated amount to your account if you have such an item.

    1 PAWEL wrote:
    Careless soldering of the short circuit.

    I solder as often as I weld - as needed :) so please don't point out :wink:
  • #6 16701899
    1 PAWEL
    Level 42  
    Posts: 7210
    Help: 674
    Rate: 1362
    I will search the internet and see what I find.

    Probably - Wltoys Potentiometer with wire plug

    https://pl.aliexpress.com/item/4pcs-B502-B5K-...le/32641944854.html?spm=a2g17.search0304.4.47. MwguOi

    https://www.aliexpress.com/w/wholesale-b5k-degree.html

    https://pl.aliexpress.com/item/Wltoys-Q333-RC...er-Connecting-line/32749460825.html?spm=a2g17. search0104.3.2.ThC92U & ws_ab_test = searchweb0_0, searchweb201602_1_10152_10065_10151_10068_10344_10342_10343_10340_10341_10304_10307_10301_10137_10060_10155_10154_10056_10055_10054_10059_100031_10099_10338_10339_10103_10102_440_10052_10053_10142_10107_10050_10051_10171_10326_10084_10083_10080_10082_10081_10110_10111_10112_10113_10114_143_10312_10313_10314_10078_10079_10073, searchweb201603_11, ppcSwitch_5 & btsid = 2b40c48f-d304-499b-8039-210499eb76e5 & algo_expid = a923f12f-be1b-4e0b-acbd-db69ffb72802-0 & algo_pvid = a923f12f-be1b-4e0b-acbd-db69ffb72802?
  • #7 16702592
    yarkk
    Level 12  
    Posts: 53
    Rate: 7
    The one from the first link has exactly the same mark, but if you compare the pictures, it has a slightly different scope of work.
    Auto WLtoys 12428 Steering Issue: Replacing CF 502 Potentiometer, Car Turns One Way Only Auto WLtoys 12428 Steering Issue: Replacing CF 502 Potentiometer, Car Turns One Way Only

    So the original work range should be less than 60 °?
    Maybe 45 ° - in the first post you pasted a photo of this, but with a different marking.

    I can even buy a few models and try, but am I going in the right direction?
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  • #9 16706359
    yarkk
    Level 12  
    Posts: 53
    Rate: 7
    This one is the closest in appearance, the 50 ° range seems to be very close. However, you need to demolish this module to separate the potentiometer - and here I am a little afraid that I will not find anything to control this potentiometer.

    B502 60 ° probably will be the best of them. If you have one for sale, I will gladly buy it back.

    Could this have a maximum working range of 30 ° one way?
    B5K 30 °
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  • #10 16706360
    1 PAWEL
    Level 42  
    Posts: 7210
    Help: 674
    Rate: 1362
    Unfortunately I only have 120 °.
    This is not with a 30 ° range, only axis position data.
  • #11 16707588
    yarkk
    Level 12  
    Posts: 53
    Rate: 7
    And can removing this embankment reduce the range?
  • #12 16707605
    1 PAWEL
    Level 42  
    Posts: 7210
    Help: 674
    Rate: 1362
    yarkk wrote:
    And can removing this embankment reduce the range?


    It won't help, this embankment is not of equal value. Just like a regular potentiometer, it works within a certain range.
    I guess it remains testing with similar parameters of potentiometers
    or https://www.aliexpress.com/item/Wltoys-12428-...4.56010108.5.9.Xsxvfh&&scm=1007.12783.72505.0 - PLN 42
  • #13 16707628
    yarkk
    Level 12  
    Posts: 53
    Rate: 7
    I also thought about this transmitter, it differs in that there is no potentiometer from the "gas" control and it is for 3 batteries and not for 4.

    Do you have this 120 ° for sale?
    If so, send data to pw.
  • #14 16707635
    1 PAWEL
    Level 42  
    Posts: 7210
    Help: 674
    Rate: 1362
    yarkk wrote:
    And do you have this 120 ° for sale

    No, because I only have one spare.
    The gas adjustment potentiometer is a trimmer that reduces speed or sets to max speed.

    link
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Topic summary

✨ The discussion revolves around a steering issue with the WLtoys 12428 model, specifically related to the replacement of the CF 502 potentiometer. The original potentiometer was found to be incompatible with the steering wheel, prompting the user to replace it with a 5 kΩ potentiometer. After initial success, the steering functionality deteriorated, resulting in the car only turning in one direction. Participants suggested that the replacement potentiometer must have a specific working range and emphasized the importance of setting the zero position correctly. Various alternatives for potentiometers were discussed, including sourcing from online platforms like eBay and AliExpress. The need for precise specifications regarding the potentiometer's range and compatibility with the model was highlighted, with recommendations for specific models such as B502 and B5K.
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FAQ

TL;DR: WLtoys 12428 steering fixes hinge on matching the pot’s rotation: “the entire range is 120 degrees,” so choose 50°–60° or 120° parts accordingly. [Elektroda, 1 PAWEL, post #16702724]

Why it matters: The wrong potentiometer range causes one-way turning, weak steering, or poor centering in WLtoys transmitters.

Quick Facts

Why does my WLtoys 12428 only turn one way after replacing the pot?

A mismatched rotation range or mis-centered pot skews the control signal. If the wheel moves ±40°, a 50°–60° rotation pot aligns better than 90°–120°. Re-center the transmitter: power on so the servo centers, then set lever and trim. [Elektroda, 1 PAWEL, post #16698492]

What potentiometer value and type replace CF 502/B502?

Use a 5 kΩ linear-taper potentiometer (B5K) designed for RC transmitters. Model-grade parts offer defined mechanical rotation stops that suit steering wheels. Avoid generic 5 kΩ knobs without correct rotation limits. [Elektroda, 1 PAWEL, post #16698217]

Which rotation angle should I pick: 50°, 60°, 90°, or 120°?

Match the transmitter wheel travel. For an ≈80° wheel sweep, a 50°–60° pot gives symmetrical steering. A 120° pot suits radios engineered for larger sweeps. “The entire range is 120 degrees” for the shown unit. [Elektroda, 1 PAWEL, post #16702724]

How do I center the steering correctly after installation?

Power on model and transmitter so the servo auto-centers. Fit the steering lever at neutral, adjust link length for straight wheels, then fine-tune trim. This ensures equal left/right throw. [Elektroda, 1 PAWEL, post #16698492]

What does CF B502 actually mean?

“B” denotes linear taper; “502” means 5,000 Ω (5 kΩ). CF labels the series/format used in RC transmitters. Choose the same value and suitable mechanical rotation range. [Elektroda, 1 PAWEL, post #16698217]

Can I use a generic 5 kΩ knob-style potentiometer from an electronics shop?

It may work briefly but often fails due to mismatched rotation range and mechanics. Model transmitter pots include engineered stops and centering alignment features that generic knobs lack. [Elektroda, 1 PAWEL, post #16698217]

Is removing the mechanical “embankment” (stop) a good way to change range?

No. The stop does not linearize motion or extend the resistive track. The pot still works only within its designed electrical range. Choose a pot with the correct specified rotation instead. [Elektroda, 1 PAWEL, post #16707605]

Where can I buy a suitable B5K steering potentiometer?

Look for RC transmitter potentiometers labeled B502/B5K with 50°–60° or 120° rotation. Users sourced them from AliExpress and RC shops; full transmitters are also available. [Elektroda, 1 PAWEL, post #16701899]

What’s the quick 3‑step procedure to replace and calibrate the pot?

  1. Install a B5K transmitter pot with matching rotation (e.g., 60°).
  2. Power radio and model; let the servo auto-center; mount lever at neutral.
  3. Set linkage for straight wheels; tweak trim for equal left/right throw. [Elektroda, 1 PAWEL, post #16698492]

Could poor soldering cause the one‑way steering symptom?

Yes. A solder bridge or cold joint can short the pot wiper or rail, biasing the steering one way. Inspect joints and clean flux residues as a first check. [Elektroda, 1 PAWEL, post #16698492]

My wheel turns about ±40°. What rotation angle maps best electrically?

An ≈80° wheel sweep maps well to a 50°–60° electrical rotation pot. This keeps the wiper within track limits and preserves symmetric response. [Elektroda, yarkk, post #16701705]

Is a 30° B5K listing the rotation range?

No. That listing notes shaft position/style, not electrical rotation. Expect designed rotations like 50°, 60°, 90°, or 120° in transmitter pots. [Elektroda, 1 PAWEL, post #16706360]

If I can’t find the exact pot, is replacing the whole transmitter sensible?

Yes. A WLtoys replacement transmitter is inexpensive and avoids fitment guesswork. One shared option cost about PLN 42 at the time. [Elektroda, 1 PAWEL, post #16707605]

What is a trimmer in this context?

A trimmer is a small onboard potentiometer used to set max speed or fine-center. It complements the main steering pot but doesn’t replace proper centering. [Elektroda, 1 PAWEL, post #16707635]

Expert tip: what single check prevents most alignment issues?

“When you turn on the model and apparatus, the servo should assume the zero position.” Always center first, then install the lever. [Elektroda, 1 PAWEL, post #16698492]
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