WARNING !!!!Problems replacing Pot's on G25 pedals.

1,067
No46_TheDoctor or SSRacingUK
Just had my accelerator pedal pot go wonky on my G25, so I ordered a few 10k pots online.

Couldn't find an with metal shafts so just got plastic ones, however !

When I installed them it seemed like they weren't traveling far enough to calibrate them, they would calibrate fine if I turned them by hand, but when installed in the pedals the pots didn't seem to be traveling far enough to calibrate.

The result is that I had to heavily modify the pedals ! After a day's work I finally have an acceptable solution giving the required pedal travel to enable the pedal to calibrate, won't go into the details of what I had to do !

Has anyone else encounterd the same issue when replacing their pots? I thought maybe I just had a dodgy pot, but they all seemed to have the same problem.

Also, does anyone know for sure what type of pots the G27 uses, I've seen somewhere that they use optical sensors but I have my doubts about that.

EDIT.................................................................

O.K. after some investigation and measuring I have discovered that the G25 doesn't use standard pots, as seems to be widely suggested on the internet !

Below is a diagram to explain what I mean, which begs the question, when all these people suggest a simple fix to a sticky or jumpy throttle on a G25 is as easy as replacing the 10k pots with ones from a local electronics retailer, have they first tried out the solution !!!!

pots.jpg



Anyway, hope this helps someone who was in the same position as me a few days ago, If I'd known that the G25 uses non-standard pots then I could have saved an awfull lot of hassle, still, I managed to come up with a solution, not pretty, but it works !

I have a feeling that maybe a 20k pot might be a better option for a replacement, they aren't expensive so I may try one when my brake pedal starts to act up.

EDIT...................................................................

Some more measurements, seems the minimum resistance change the G25 needs to see from a pedal pot is around about 3.5k , so a 20k pot should work ok given the limited movement supplied by the pedal, have ordered some 20k pots and will post results.

Update................................................................

22k Pots arrived today, they just work and no more, it's quite difficult to find good quality pots for some reason and I think the ones I have aren't the most accurate, one thing I have noticed though is that the G25 will register resistance all the way up to 22k and maybe beyond, meaning that if I can figure out some way of getting the pedal stroke to opperate the full range of the pot it will be a very accurate pedal indeed.

Some more measurements and better quality, maybe larger resistance pots required to finally get this sorted, I'm toying with the idea of building my own pedals to be honest because most of the probelms I am encountering are down to the design of the G25 pedals..........
 
Last edited:

the_greeze

Cookin' on gas!
Premium
1,008
United Kingdom
UK
the_greeze
That's a good find mate, cheers. :) I'm going to order some of these for spares. 👍

Too bad you had to go through all the heartache of modifying your pedals before finding them though... :(
 
360
GTP_Joeninety_ (TT-R Driver)
Cheers Doc:tup:
My brake has just started playing up and i was hoping there would be replacement parts....hopefully something abit closer to home(NZ)
 
You dont always need to get new pots, my accelerator pedal went wonky recently (typical that when GT5 is imminent my G25 decides to throw a wobbly) and just cleaning the pots up with some WD-40 seems to have done the trick (for now).

I would recommend trying that before you start getting the soldering iron out :)
 
1,067
No46_TheDoctor or SSRacingUK
You dont always need to get new pots, my accelerator pedal went wonky recently (typical that when GT5 is imminent my G25 decides to throw a wobbly) and just cleaning the pots up with some WD-40 seems to have done the trick (for now).

I would recommend trying that before you start getting the soldering iron out :)

You should use proper switch lubricant, but yeah, cleaning them will give you an extension to their life, although replacing them isn't a major job when they do eventually die.
 
648
Gyles69
Another solution that worked for me (as I do not use the clutch) was to swap the clutch pedal with the accelerator pedal and swap over the springs 👍

I also tried electrical contact cleaner which did the job but would only last 2 weeks.
 
362
United Kingdom
London
MadHax
M8DH8X
Hello Doctor, I am in urgent need of 3 potentiometers. Could you post the links of where you got them from, I tried thesimshop and they seem to have non in stock.
 
76
Leprekaun
Great post! Thanks for the insight No46_TheDoctor! Sorry you had to go through the hassle of modifying your pedals to get it to work with the pots.

I ordered 3 pots from that website (thesimshop.com) but they didn't work properly. The throttle pedal doesn't respond at all in the game control panel in Windows and the brake and clutch reach their maximum (like only pressing the pedals halfway registers as maximum in the game control panel). I've checked to make sure that the wires are connected correctly and they are definitely connected to the right connectors on each pot (VCC top, signal middle and ground bottom) so the three top connectors on each pot for each pedal is definitely VCC, ground is definitely correct and the signal wires are connected correctly to the corresponding pedals. So I don't know whats wrong with my setup so would you be able to offer any insight into this? Could it be that I got a batch of bad pots? Although my brother, who's a computer engineer, believes that the likelihood of getting 3 bad pots is near impossible.

When my brother measured the resistance of the pots using a multimeter, he noticed that the variation in resistance between maximum and minimum was much greater with the old, original pots than with the new replacement ones so he believes that what could be happening is that the G25 is expecting a certain difference of variation (like 0.4 k ohms between maximum and minimum resistance) but the pot only varies by like 0.2 from minimum to maximum so the G25 doesn't recognise it.

So can you offer any light on this?
 

mrbasher

BasherBoards!
Premium
1,358
United States
Redmond, WA
mrbasherman
The resistance of the pots should not make a difference for this purpose because they are set up like a voltage divider. All that matters is the difference in resistance between the two "sides". If the pot is set in the middle, you have 50% voltage going out the wiper pin because the resistance on both sides of the wiper are the same. Moving it in either direction changes makes the voltage on the wiper pin go up or down. (Sorry, just wanted to make it clear what's happening) :)

Most pots are set up so that ground and V+ go to the outside pins and the "signal" comes out of the middle pin. Is that how you have them connected? Any other way and they will not act as expected.

Reversing positive and negative on the outside pins will reverse the direction the voltage as you turn the pot.

Hope that helps.
 

mrbasher

BasherBoards!
Premium
1,358
United States
Redmond, WA
mrbasherman
Also.. If you know the value of the pot (10k or whatever) but don't know which pins are which, here is the simplest way to find the wiper pin:

Turn the pot to what feels like the middle.
Check the ohm reading of the pins until you find the combination that equals the value of the pot.
These two pins are your positive and negative pins, the other pin is your wiper pin.
 
76
Leprekaun
Thanks for the replies and info mrbasher. I am certain that the wires are connected to the correct terminals of each pot. There is no 2 ways about it, they are definitely in the connected to the correct terminals.

Just to clarify a bit on my previous post, what I meant by maximum and minimum is in regards to pedal travel and varying resistance. So I'm saying that when the pedal is fully depressed, the resistance reading difference between 0% pedal travel and 100% pedal travel of the signal wire is different from the resistance reading from the signal wire of the old pot when applying the same test. Also, after speaking with my brother, he noted that difference in the resistance readings weren't as small as I stated. The difference (0% pedal travel to 100% pedal travel) between them was more like 1 kohm with the new pots while the resistance reading difference with the old pots was more like 3 kohms.
 

mrbasher

BasherBoards!
Premium
1,358
United States
Redmond, WA
mrbasherman
That makes sense... However, it really shouldn't make much difference to the wheel. I say "shouldn't" because I don't personally have a set of these pedals to test this with, I'm working on the theory here. :)

Here's what I would suggest: Instead of measuring the resistance on the pot, I would connect the pot and turn on the wheel with the signal wire disconnected. Put the voltmeter's negative probe on the negative terminal of the pot. Put the positive terminal of the voltmeter on the signal terminal. Now turn the pot and take note of the minimum and maximums. Then do the same with the old pot. Make sure to turn it slowly since your old pots aren't working right.

The results SHOULD be the same... If they aren't something is most likely not connected right.

Check the polarity of the pot that's working with your voltmeter and make sure the others are the same. If you are 100% certain that you have the wires connected properly to the pot and you know which wire is which, you can try swapping the positive and negative wires on the pots that aren't working for the sake of checking. The only thing I have to check this with for you is a set of DFGT pedals and a wheel. Sorry I can't be of more help.

All that being said, it should not matter. Like I said, the pot works on a voltage divider concept which is super simple. It's no different than taking two resistors and connecting one end of each, then connecting the other ends to positive and negative. The voltage coming out of where the resistors are connected to each other is based almost purely on division of the values of the resistors. If both are 10K, and you are putting in 5 volts, you'll get 2.5 volts out of them If both are 100k and you put in 5 volts, you still get 2.5 volts. The only real difference is the current. However, the wheel shouldn't give a darn about the current unless it's so low it can't register anything at all.
 
203
biben
Hello everyone, I have the same experience of OP,but mine is G27. I ordered 3 10k pot from the sim-shop (that's No46_TheDoctor Posted)few months ago for brake pedal replacement, I suppose G25 and G27 are using the same pot, but I'm wrong.
First, the fitting hole size are different, G27 have a smaller hole.
So I must do some work to make it wider.
After I installed, it can't be calibrate because the traveling distance not enough.
So I try offset the gears, it's work, but have a problem, the brake pressure run 100% at 90% brake traveling....It's can't be accept.
So, finally I open the old original pot, clean it up, installed it again. Now it work like new.
 
1,067
No46_TheDoctor or SSRacingUK
Sorry to hear you guys are having problems with those pots, I wouldn't have recommended them if they hadn't worked perfect for me.