Cruise control issue. (1 Viewer)

[Charlie Farley]

I Have noticed what appears to be a fault with the cruise control, when on a long slight incline the comformatic box doesn’t change down to maintain speed, it simply drops out completely. All other motors I’ve had a still own with conventional auto boxes change down without issue.
Has anyone else experienced this?

 

[EuroTrotters]

Hi

If the engine and powertrain cannot cope with the load, it may kick out.

Examples:

Toyota 2.4 DOHC 138BHP, kicks out at full payload on hills.
Mercedes 5.0 V8, 356HP, never kicks out at any load/hill
Mercedes Sprinter 2001 Model year 416CDi 4600kG rarely drops cruise
Mercedes Sprinter 2013 Model year 528CDI 5000KG Often drops out of cruise.

Common reasons:

Final Drive
Gearbox Type
Power
Load
Steep Climbs

Could be faulty mind

TM

 

[Charlie Farley]

Thanks for the info TM, my brother has an AT with the same 3l engine and transmission and his changes down with the cruise set then up again when on the level.
My guess is a software issue.

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[Steve N Tracy]

Our 2017 150 bhp Comfortmatic changes up and down on long inclines while using cruise mind you it changes down later then I would if driving a manual.

 

[Jo662]

Our comfortmatic cruise control drops out when going up steep hills as well. I was told it’s best not to use on hills.

 

[peterc10]

I Have noticed what appears to be a fault with the cruise control, when on a long slight incline the comformatic box doesn’t change down to maintain speed, it simply drops out completely. All other motors I’ve had a still own with conventional auto boxes change down without issue.
Has anyone else experienced this?

I have the same issue. My Fiat Pro dealer tells me that they have come across this before and reported it to Fiat who told them that is how it works and there is nothing they can do about it. You can make it work by just putting your foot down on the accelerator which will allow it to drop down a gear and when you get to the top just let off and the cruise kicks back in. TBH it is a bit annoying but that is just what I do, or I just go slower up the hill to save some diesel.

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[joka250]

I would suggest trying the UP feature when on an upward incline. For the first 2years of ownership I never used it now I do. Don't know all details but vehicle in auto and cruise performs more consistently and predictably. Button is just forward of gear select.

 

[Cavs]

mind you it changes down later then I would if driving a manual.

I agree with you. All three of my Comfortmatics would change down when in cruise and climbing, but IMO left it too late, so needing a bootful in the lower gear to get back up to speed. Now, if I feel that it should have changed down but hasn't, I nudge the gear lever to change down, which makes for a smoother (and I suspect more economical) drive.

 

[peterc10]

Now, if I feel that it should have changed down but hasn't, I nudge the gear lever to change down, which makes for a smoother (and I suspect more economical) drive.

Interesting idea. But does that knock it out of cruise?

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[Cavs]

Interesting idea. But does that knock it out of cruise?

No. You can use it fully manual without causing the cruise to disengage if you wish.

 

[peterc10]

I would suggest trying the UP feature when on an upward incline. For the first 2years of ownership I never used it now I do. Don't know all details but vehicle in auto and cruise performs more consistently and predictably. Button is just forward of gear select.

I have "up" on permanently on the recommendation of Andy @Techno who says it saves wear on the clutch.

 

[Techno]

The up function was designed for steep hills or heavy loads. A motorhome isn't an empty white van, it is heavy all the time.

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[Mr Colpot]

I havent noticed mine dropping out on an incline but it hasnt dropped out as far as I can remember so possibly not! It does change down if I up the speed to pass traffic though. I also run mine in Up mode all the time as I did some tests without and it is a tad more economical in up (it may be 3 mpg but every little helps)

 

[Techno]

I never accelerate in 6th unless extremely slowly. Always knock into 5 or 4 if you intend a fast overtake.
I don’t wait for the computer to make that decision as it will try first which is the culprit in clutch wear IMHO

 

[tonyidle]

Whether it happens or not will depend on the interaction between the cruise control & Comfortmatic design settings. Cruise controls drop out when they cannot maintain the set speed. The drop in speed allowed before this happens is normally set by the manufacturer. The gearbox changes down dependant on load, accelerator position, and engine speed. If the down-change doesn't occur before the cruise controls drop-out speed then the cruise control will disengage.

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[Charlie Farley]

Thank you all for the advice and guidance. I have now had the opportunity to test the “Up” function and indeed the cruise works and performs as id expect. I will now be using the “up” function permanently as the box hangs onto to the gears slightly longer and gives a smoother change.

 

[filopastry]

Fiat Ducato 2.8jtd with fully auto box and she does the same, not all the time, sometimes she changes down and just occasionally it trips out ... don't know why but now I keep the right foot over the accelerator ready to push down should she "drop out". Glad I'm not the only one, gearbox was changed just before we bought it so only done 3000kms. Ours is not a factory fit but after sales fit

 

[buttons]

Using the throttle on steep inclines to get it to change down before it starts to labor should keep cruise engaged.

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