Different speeds using cruise control or HST pedal with auto throttle advance engaged

[rogerius]

Hello,
I'm close to 50 hours on my L3940HST and here is my dilemma: using the tractor at a same RPM and same speed range, I've got different speeds if I use my cruise control or I use the HST pedal with Auto Throttle Advance engaged. Can somebody confirm if this is okay?
Thx

[94BULLITT]

I'm not sure I completely understand, So at the same rpm with hydro pedal at the same place your tractor does not go the same speed a the using the pedal with the auto throttle?

Maybe stall guard was kicking in?
Maybe you were in a different range with dual speed hydro? If you advance the cruise at too low of a rpm it will automatically down shift.

[JOHNTHOMAS]

I had a L3240 with the auto throttle and I believe yours is working properly. I believe the auto throttle takes control over all other settings when you push the pedal. Not sure what your saying about the cruise control which should maintain near the same speed if your NOT touching the foot pedal.

[TripleR]

I don't remember who, but someone posted on adjusting the auto throttle to suit them, so it appears it can be changed from factory settings.

[PHILIP8N]

Hello,
I'm close to 50 hours on my L3940HST and here is my dilemma: using the tractor at a same RPM and same speed range, I've got different speeds if I use my cruise control or I use the HST pedal with Auto Throttle Advance engaged. Can somebody confirm if this is okay?
Thx

What operation are you performing with your tractor? Are you mowing? Turn the auto-throttle off if you have pto engaged, I do not like auto-throttle and pto on at same time, do not think was intention of design. Set cruise at your mowing speed. If you are below max speed in that range using cruise control, you can override to higher speed with hst pedal.

Philip.

[TimP]

I have a B2150 with the "Cruise Control" and it acts the same way.

Using the Cruise Control is always a little slower or less RPMs, than if I use the Hydro pedal.

[crazyal]

I'm not understanding the question. The auto throttle is just a cable that bumps up the engine RPM when you push the HST pedal. When you engage the lever it connects the cable to the HST pedal. You can adjust the cable to change the engine RPM, it's pretty easy. But the Auto throttle has nothing to do with the cruise control. The cruise control lever is variable, just like the HST pedal. The further you move it forward the faster you will go. If it's out of adjustment you may not go as fast when it's all the way forward (it's not hard to adjust) than the HST pedal but that's not anything to worry about.

[PhilY]

I've got the L3540...with Auto-Throttle-Adv (ATA), the tractor does not move quite as fast as it does with ATA off. This is normal and gives you a little more power in the low end. Reason being is that the engine rpms are near idle when using ATA. You might bump up the hand throttle a little to help with FEL hydraulics if you're wanting to dump or something when the tractor is not moving as your foot is off the pedal. Due to this I think they let you get the engine rpms a little higher in ATA so you have the power you need when operating at slower speeds. You can adjust this though. There are 2 throttle cables going up to the engine. The upper one I believe hand throttle, the lower is foot throttle. If you let it out, I think it was, then the HST speed sensor in the foot pedal when engage sooner and therefore the tractor will move a little quicker across the foot throttle spectrum. Cruise control just is a secondary foot pedal HST sensor. From my experience, when in HST mode, I can't notice a difference in speed between the cruise lever and foot pedal. Haven't tried using cruise in ATA.

[rogerius]

PhilY, thanks for explanation.

I tried some experiments this weekend to give you real data (no PTO used, no stall guard engaged, flat road).
1. if I have Auto Throttle Advance ON and I use just the HST pedal, at 1900RPM I can reach 5.1mph
2. if I adjust the manual throttle at 1900rpm and I use just the cruise control I can reach 10mph
So I hope now is clear what I ask. I don't understand how the cruise control is working as if the throttle is constant, what the cruise control is doing? doesn't have the same role as the HST pedal?
Thanks for your patience.

[kuboman]

The cruise works independent from the pedal. All hst functions are controlled electronically. The auto throttle is connected to the hst pedal and will only operate if the pedal is used.