High Speed Idle

[budbud7]

Guys I need some help. Just got back from a trip from Mississippi yesterday and heading out to Galveston today. My high speed idle does not work any more. I only use it when I'm stopped for a while with the a/c on and interior lights.
1. where is this solenoid or relay located?
2. Is there any harm just letting the bus idle normally with the a/c on and lights?
3. Could there be another problem to make the high speed idle not work.

I will check back with this forum when I get to some location with wi fi. My bus is 1999 Thomas RE, 5.9 Cummins, 24v. Thanks

[Brad_SwiftFur]

Originally Posted by budbud7

Guys I need some help. Just got back from a trip from Mississippi yesterday and heading out to Galveston today. My high speed idle does not work any more. I only use it when I'm stopped for a while with the a/c on and interior lights.
1. where is this solenoid or relay located?
2. Is there any harm just letting the bus idle normally with the a/c on and lights?
3. Could there be another problem to make the high speed idle not work.

I will check back with this forum when I get to some location with wi fi. My bus is 1999 Thomas RE, 5.9 Cummins, 24v. Thanks

Check brake lights. Often the high idle is a function of the cruise control and will disengage when the brake is pushed (or, more specifically, when the brake lights are activated). You could have a failed or out-of-adjustment brake light switch. If it has hydraulic brakes, the switch is usually right above and behind the pedal (it's not uncommon for the switch to wear at the contact point, eventually leading to brake lights staying on); if it has air brakes, it has an air pressure sensor not far from the brake valve.
If it's a manual transmission (or for anyone who has one), the same usually holds true for pushing the clutch. If it's an automatic, it could be sensing (or failing to sense) the transmission is in neutral; check the neutral safety switch (unlikely, but you never know ...) And finally, there may be a fuse/breaker for the cruise control circuit itself.

[budbud7]

Thanks for all of the good info. I think the problem was my fault. Prior to getting on the road, I couldn't start the bus. After about 20 minutes of looking and trying, I found the bus to be in DRIVE, therefore the start switch was locked out. After I got on my way I figured that being in DRIVE, prevented me from engaging the high speed idle. My brakes were set so I didn't think of DRIVE. At the next stop I tried to engage the High speed idle and it worked!!

There is a lot that I'm going have to learn diesel eng., trans., and the whole bus thing to be a good RV'er. Thanks again.