2008 Gem throttle

Thought I better start my own thread.

  1. Throttles seem very repairable.
  2. Saturn throttle is a good mechanical fit. Same Delphi 10p plug. (6p wired) Bad choice electrically.
  3. The internal switch can be easily replaced with micro switch or prox/reed nc switch. (window alarm magnet. Internal or external.
  4. Electrical diagram: (corrected)

I suggest as a first step repairing throttle to wire a nc switch from :slight_smile:

Hi Inwo
thanks for info i have a pedal without switch can take picture inside if it will help

here are some info a guy hacking Gem pedal

I’m still making corrections to Gem drawings, as +5v and Ground are reversed somewhere.
I guess I will have to look at my car. :frowning:

The throttle internal I’ve corrected.
When wired per diagram for testing, more throttle moves nearer 0v rather than to +5.

I’ll stick with it now. I’m on a quest.

The throttle plug colors are correct. I’ll have to check the other end to see if they are reversed from Gem diagram.

All is wired correctly from the diagram. It’s the + an - reversed for controller pin numbers on Gem diagram when compared to T4 pin-out.
T4 specs:
image

Gem diagram:
image

I’ll correct previous diagram.

The internal centering resistors on the 2.5k pot are to prevent damage if mis-connected.
They will always have at least 100ohm in series. A normal pot goes to zero and would burn out when near zero ohms.
I think I have everything I need.
Now to decide whether to send the Saturn throttle back or put a switch in it. ???
Anyone need a throttle?
I don’t want to remove mine, and can’t test in the car until I get a 10’ wire extension.

This is looking into the throttle plug:
2008%20gem%20throttle

Almost there. The Saturn uses the same pin-out. That’s a plus.
A simple internal modification sets it to the correct .25v to 4v range.
No idea on linearity.

Saturn uses some type of resistance change for switch. I should be able to use that to make a solid state
start switch.

Now I have a solution for a problem that I don’t have. :slight_smile:

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Hi
it look like they use resistance change for switch on new type pedal on 2013 Gem cars

how looks Saturn diagram,same as this picture ?
but with other connector

4

this is from 2013 manual

Can you find that information for other cars, or dorman throttle pedals? Make my quest much easier.
The Saturn pedal may not be the best choice. The pin-out and socket is correct. Mechanically good, use the Gem lever on the Saturn pot box.
I doubt that the internal mods will be a diy project.

Function wise that is correct for my Saturn pedal. However there are many resistors that set the range and linearity to exact specs that are not compatible with Gem. The voltage swing is confined to a small part of 0-5v.
Switch is straight forward on-off for Gem. All I need is an open collector switch that will pull pin 3 to 0v when pedal is off-idle.

Not sure what to do with it if it works. Might be best to use it myself in case it needs fine tuning.

I paid too much.
Rock Auto price.

After bolting on the Gem pedal.
image

Extension cord for testing. M-F

Or just buy this one.

Success, seems to work perfectly.
If someone wants to build these, I can share what I learned.
New Gem throttle for < $100 in parts, and a few hours work. Next one, I may find a short cut. First one is always pita.
The harness is pretty handy for testing. Might be something for service guys.

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Yes glad to hear you have a proof of concept with the saturn accelerator module! Would love to know more, did you end up using the open collector switch? As well how did you modify the voltage range?

Yes, not for the faint of heart. Next one will go better.

Switching transistor shown in upper right. EBC connected as shown.

Right hand pad is zero ohm contact to wiper.
Adjacent pad is about 800 ohms.

Next 2 pads are 2nd pot. Remove enough material so as wiper runs off pad to make a switch.

Extreme left square pad is 160 ohm from +5v. It limits “top” voltage to 3v on main pot.
It also limits current to base from switch.

Jumpers connects from +5 resistor to both ends 2nd pot/switch.

I messed around with a lot of things to get proper range of <.5v to ~3v
I have a feeling it was not needed. If it is, it’s quite easy to manipulate with some of the built in resistances.

Someone please copy this method before I buy a dozen Saturn throttles and start another business! :slight_smile:

Part numbers to make extension lead.

Wanted 2 of each, but messed up and only ordered 1 male end.
I am short weather seals. Not needed.

More information to follow.

Nice Inwo
do you think i can do same with my Dorman 699-100 ?

Mine is 699-138.
Look close electrically. Don’t know what the dots are on your pot traces.
Who knows, may work better than mine.
I’ll take you through it if you want to try. Else send it to me and I’ll see what I can do.
Will you test voltage range of a stock gem, to verify my findings?
Maybe I’ll start a new business if no one else wants to. :slight_smile:

1 Like