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Cruise/idle not working


redcrzr

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I have searched the forum for answers to no avail. My 99 Volvo w/Volvo D12 has a non functioning cruise control and therefore the high idle is also non existent. I have inspected wires, looked for a fuse (which I did not locate). Any ideas as to where I should look? Is this a problem for a "real" mechanic. I should add that the cruise has worked in the past although at times it hasn't. I don't remember the high idle not working.

Thanks,

Todd E.

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My cruise control will not engage at times unless i hit the brake. There are times when I leave somewhere and never really have to stop before getting up to cruise speed. Try pushing firmly on the brake. My truck is a 2001 with a D12 also.

 

Rod

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Brake and/or clutch disengage switch might be inop or out of adjustment. Remove trim panel from under driver dash area including the panel under the steering wheel to access the switches. On a gen 2 truck the switch is a small micro switch with a "spring" arm that "touches" the brake or clutch pedal to activate the switch when you apply the brake or clutch pedal. Some times the "clip" that holds the switch to its bracket will break and allow the switch to move out of position. They have since changed the "clip" to little mounting screws. As I said this a gen 2 style truck so gen 1 might be different but the concept may be similar.

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Scott may be on the right track. I had the same problem with mine. Before pulling anything apart, try lifting/pushing the brake pedal (truck not running) and listen for the switch to click. If the click happens above where the pedal normally rests, that's your problem.

 

Unlike a lot of cars, the brake lights and cruise control use 2 separate switches--the brake lights have an air pressure switch, and the cruise control is connected to the pedal.

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Thanks for the 3 replies. I will get to it on Thursday, it's getting pretty close to "happy hour" here. I will repost when I can.

I was messing under the dash a couple of weeks ago with water leak issues, I may very well have knocked up against such a switch.

Todd E.

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My cruise control will not engage at times unless i hit the brake. There are times when I leave somewhere and never really have to stop before getting up to cruise speed. Try pushing firmly on the brake. My truck is a 2001 with a D12 also.

 

Rod

On my truck as the manual states, the system has to see a "brake functional safety test" each key cycle. It means the brakes have to be applied for 4 seconds after the truck is started or the cruise will not engage. On mine there is a switch on the clutch but not one on the brake pedal, it reads the brake signal from the air switch brake light circuit.

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I would first look for any error codes. That could be a bigger clue to what's going on. Even intermittent errors can break the cruise control lock. For instance, an intermittent problem with the throttle position sensor can cause this. It might be intermittent enough to not be noticeable in operation but all it takes it one glitch of it to lock out the cruise control and the Jake brake.

 

If that is the original TPS then it could easily be getting noisy (like an old time volume control on a radio or TV). I struggled with mine, opened and cleaned it and it improved for awhile but ultimately had to replace it. Once I did, no more cruise control or Jake drop outs.

 

Just a thought.

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All your suggestions & comments are appreciated and extremely helpful. I have a fair amount of play in the brake pedal & I could hear the switch operating as suggested above within that range of play. I was able to adjust the switch enough to have the high idle engage again & I suspect that will also clear up the issue with the non-functioning cruise control. My '99 has a bolt adjustment.

The comment about Mark's schematics-I did take a look there & couldn't see anything that made sense to a guy with my abilities. Now that it appears to be fixed, I may take another look & see if I can make some sense out of the diagrams.

YOU GUYS ROCK

Thanks for saving me some money. Safe travels,

Todd E.

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Depending on you truck build date, check out these two links:

 

D12 Engine build 2.99 http://www.dmbruss.com/images/Schematics/V4_PV776_370_98184_1_EngineBrakeCC_VolvoD12B_VN_B2_98.pdf

D12 engine build 5.99 http://www.dmbruss.com/images/Schematics/V5_PV776_370_98184_2_EngineBrakeCC_Volvo_D12_VN_B5_99.pdf

 

SHow you the Engine brake and CC wiring--at leat you can see how the switches are connected and stuff!

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