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Diagnosing Speed Control


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If it appears on my door step, I won’t turn it down :nabble_smiley_teeth:

Truly though, I sincerely appreciate the offer.

I'll slip an amplifier in the box with the servo. If you have a good cable you should be able to make it work with some combo of those parts. :nabble_smiley_good:

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I'll slip an amplifier in the box with the servo. If you have a good cable you should be able to make it work with some combo of those parts. :nabble_smiley_good:

Chris - This is going out today:

  • Servo: I can't test this one as I don't have a way to do so, but it does pull in with vacuum and doesn't appear to leak. And you can see how the cable goes on, with the bullet on the end of the cable going into that clip in the middle.

  • Amplifier: I know this one works as it has the hole I drilled in the case, circled in red, in order to get to the potentiometer to adjust it. That pot determines how close to the current speed the set point will be when you hit Set. I have one that I've written on that says "Jumps 6 MPH", which means it works but is no fun. This one was adjusted to pick up ~1 MPH on Big Blue, but it may be different on your truck so you may want to adjust it.

  • Pickup: This one is from Dad's truck so I know it worked as I used it a bunch. (Don't worry as I'm going with one of the tranny-mounted units when I build Dad's truck.)

  • Relay: I thought about not sending a relay, but having re-read this post where I tried a standard Bosch relay and found that the speed control didn't work I decided you might need this. It is also from Dad's truck so I know it works. But I couldn't find another one, although I should have one, so don't let it get away if you don't need it.

More_Speed_Control_For_Chris_-_II.jpg.448586a4055478a29aefbeb66d66feaa.jpg

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Chris - This is going out today:

  • Servo: I can't test this one as I don't have a way to do so, but it does pull in with vacuum and doesn't appear to leak. And you can see how the cable goes on, with the bullet on the end of the cable going into that clip in the middle.

  • Amplifier: I know this one works as it has the hole I drilled in the case, circled in red, in order to get to the potentiometer to adjust it. That pot determines how close to the current speed the set point will be when you hit Set. I have one that I've written on that says "Jumps 6 MPH", which means it works but is no fun. This one was adjusted to pick up ~1 MPH on Big Blue, but it may be different on your truck so you may want to adjust it.

  • Pickup: This one is from Dad's truck so I know it worked as I used it a bunch. (Don't worry as I'm going with one of the tranny-mounted units when I build Dad's truck.)

  • Relay: I thought about not sending a relay, but having re-read this post where I tried a standard Bosch relay and found that the speed control didn't work I decided you might need this. It is also from Dad's truck so I know it works. But I couldn't find another one, although I should have one, so don't let it get away if you don't need it.

Thank you Gary! I'm looking forward to having some goodies when I come home from this work trip, although my wife and/or kids will ask "What truck parts did you order now?" :nabble_laughing-25-x-25_orig:

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Thank you Gary! I'm looking forward to having some goodies when I come home from this work trip, although my wife and/or kids will ask "What truck parts did you order now?" :nabble_laughing-25-x-25_orig:

I'm hoping it'll be there when you get there, Chris. Enjoy!

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I'm hoping it'll be there when you get there, Chris. Enjoy!

So I have made some progress (which is good!)

I went to swap out the amplifier in the cab - and while under there, noticed there is nothing to actuate the vacuum dump valve! I think it may be called a "brake pedal adapter" but can't find much yet in the parts catalog (I still have a hard time finding stuff there). It looks like something was mounted to the pedal at one time but was broken off????

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So I have made some progress (which is good!)

I went to swap out the amplifier in the cab - and while under there, noticed there is nothing to actuate the vacuum dump valve! I think it may be called a "brake pedal adapter" but can't find much yet in the parts catalog (I still have a hard time finding stuff there). It looks like something was mounted to the pedal at one time but was broken off????

Your assumption is correct. The pad that pushes the little white plunger is missing/ has been removed. I’ll send photos when my devices synch

 

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Your assumption is correct. The pad that pushes the little white plunger is missing/ has been removed. I’ll send photos when my devices synch

Yep. I may have an extra one of those, but you can at least get the thing working w/o it. So maybe get a bit farther and see if there's anything else we missed and in the interim I'll see if I have one.

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Yep. I may have an extra one of those, but you can at least get the thing working w/o it. So maybe get a bit farther and see if there's anything else we missed and in the interim I'll see if I have one.

Yep, agreed! It was just a surprise to see it completely missing!

The PO told me several things when I bought it back:

A/C didn't work... (worked when I sold it)

Cruise Control didn't work... (worked when I sold it)

I think he got amnesia about all the things that broke while he had it, or tried to fix... :nabble_smiley_uh:

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Yep, agreed! It was just a surprise to see it completely missing!

The PO told me several things when I bought it back:

A/C didn't work... (worked when I sold it)

Cruise Control didn't work... (worked when I sold it)

I think he got amnesia about all the things that broke while he had it, or tried to fix... :nabble_smiley_uh:

Well I hooked everything up, and did a road test. It didn't hold speed, or accelerate. I'll start running more tests, hopefully tomorrow.

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Well I hooked everything up, and did a road test. It didn't hold speed, or accelerate. I'll start running more tests, hopefully tomorrow.

Make sure that vacuum line going to the valve on the brake pedal isn't open. That's a dump valve and needs to be sealed for the system to work.

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