Problem with fiat comfort-matic gearbox and cruise control (1 Viewer)

[peterc10]

I have a new A class with 3litre Fiat engine, comfort-matic gearbox and factory fitted cruise control.

The cruise control works great on the flat and slight hills, cruising along in 6th with no problem. However as the hill gets steeper it slows down and eventually if the hill gets too steep it just gives up and switches cruise off. It appears that the problem is that the auto box will not drop down to 5th in order to maintain the set speed.

Is this usual or do I have a problem that needs fixing. I have had similar semi auto boxes before and they always changed down in these circumstances.

 

[pappajohn]

My thoughts are cruise control management module fault.
Possibly getting no engine load input from the ECU.

 

[DBK]

When you say new do you mean brand new or new to you? In either case get back to the dealer and have it fixed under warranty. If a private purchase then you are going to have to pay yourself to have it fixed as there is definitely a problem. You could see if the seller will contribute, worth asking.

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[peterc10]

New as in new last November. Wanted to know if it was a characteristic of the gearbox or a problem. If a problem I will take it to my local Fiat Pro dealer, who is a lot closer than the dealer I bought it from.

 

[dave newell]

I don't know how the comfortmatic is set up to work with cruise control but I would have expected under the conditions you describe for the cruise to apply more throttle to maintain speed, all the way to 100% if required. Ordinarily I would expect this to cause the box to change down a gear. It would appear to me from your description that there is an issue with the gearbox ECU not changing down. If you drive it manually (i.e not on cruise control but gearbox in auto mode) at the same cruising speed and hit a hill so apply more throttle to maintain speed does the box not downshift? Worth a try to establish if its the cruise system is not applying enough throttle or the gearbox is not making a downshift when it should.

D.

 

[DBK]

I think the above would be a very good test. But you do have the 'box set to auto, with the A appearing on the dashboard? It will change down in manual mode but not before the engine revs have dropped right down.

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[Sheddy]

Mine does the same, the cruise control gives up on relatively medium hills when in 6th gear with the CC set at 90 kmh, I think it is a speed issue, as the speed drops off on the hill because the vehicle cannot maintain the selected speed, even if the robotic box changed down it would not maintain the selected CC speed, in the last 2 days crossing central France which is very up and down it has happened regularly, now I anticipate it and switch off CC and auto when the revs drop below 1800 ish, this also helps stop the gearbox trying to change up and down unnecessary with slight changes in incline, and it allows me to drive without excessive wear on the clutch. The system is fine on the flat and works well however on hills it does struggle.
Cheers
Ed

 

[Techno]

If mine is in AUTO mode with cruise it will change gear BUT it over reacts to inclines that you would go over in 6th if you were in control. So I never use the cruise but if I did I would use it in manual mode so it cannot change gear unless I want it to.

 

[Techno]

I would add that I find the accelerator pedal effortless and well balanced for cruising unlike earlier vehicles

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[TheCaller]

However as the hill gets steeper it slows down and eventually if the hill gets too steep it just gives up and switches cruise off.

So what happens at this point? Does the cruise switch off & the revs die away because you don't have your foot on the throttle? If you then accelerate does the box now change down & pull away in normal auto mode?

I don't normally have the cruise control on if I'm on a hill steep enough to require a gear change, but from what I remember from being in a motorway roadworks 50 limit (when it's hardly made it into 6th even on the flat), it changed down & then up again as required when we got to a hilly bit.

Mine is the 2.3l 150bhp engine, rather than your 3lt.