MFD touch screen works - Buttons Do Not (Climate, Info, Display, Audio)

Before you do anything drastic, be SURE that one of those 4 buttons is not sticking in the operated position sometimes.

 

I don't know. But I have had 3 Prii with sticky climate control buttons.

 

Well you can pretty easily tell that the buttons are moving IN when you push them......but it is much harder to tell if they are coming back OUT an appropriate amount.

In my case, I'm pretty sure that problem was caused by a stray drop of something like Coke, so the "fix" was wiping with a damp cloth followed by a blast of air and a tiny squirt of silicone spray lube (which dries DRY).

 

The combo meter isn't related. Sounds like you might actually be fortunate. Lots of people, including me, have had to replace the MFD lately because it just ceases to start up at all, but it sounds like yours might just have a bad connection. To check it, you'll have to remove all 4 vents, the panel above and below the steering wheel, and the two screws on the sides of the MFD, pull it out, and make sure the long thin connector on a smaller taped cable is solidly seated. I would suspect a loose connection before I would suspect a failure in the MFD in this case just because that's not a common failure mode.

 

The plastic gets cooked by years of sunlight exposure and do get fragile, esp at the top. I use 2 "trim removal tools" at once. These are plastic lever tools molded in different shapes and thicknesses to pry on things without scratching- typically sold in a set. So one tool goes under the edge of the vent mid way up the side that you can access while the other tool goes at the top edge. Do most of the prying at the center but gently "follow" each bit of movement with some at the top.

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Assuming the Prius MFD is designed like most such things those 4 buttons ether go to a dedicated 5 connector jack or to 5 pins on a larger jack. They probably share a single ground and the other pins pull the respective circuit down to that voltage when the switch closes. Sometimes the common pin is +V instead, but it is the same concept. When the common pin connection gets flaky, for whatever reason, the "all buttons fail at once" symptom is observed. So if I had to guess, there is a bad connection on that common pin, probably at the MFD, but possibly at the other end, wherever that is, of the cable. Variants on this theme include an intermittent short or open in the common line.

For starters I would figure out which connector is involved, pull it at the MFD end, and spray both the jack and the plug with contact cleaner. Be sure the windows and/or doors are all open and put a cotton towel underneath to catch the drips. Most of those cleaners seem to be xylene based and some plastics do not take well to that solvent. (But in my experience, those are never used on electrical connections.)

 

I had no trouble with the vents being particularly fragile, although my car spent its whole life in Iowa, so YMMV. I just popped the bottom out and then the top.

In regards to the type of connector and where it goes, all the button cables join together into one taped cable with a long flat probably 10-pin connector which connects to the back of the MFD board. That connection is what I would suspect to be the issue, although the cable itself is another possibility. I wouldn't expect a failure of the board at all because as I said that's not a failure mode that's been seen before.

 

Switches do sometimes fail in the closed position. So although the external button still goes up and down it does not mean that the switch beneath it is necessarily changing state the same way. If you can figure out which pins are involved you may find one ground to switch pair is always shorted together.

By coincidence, our clothes dryer "start button" failed in exactly this way yesterday. Now as soon as we twist the timer away from stop it immediately starts the heater and drum, without having to push that button. This mode of failure is a bit more common in high voltage devices, where the contact spark may weld the conductors in the switch together.

 

Well, if they all share the same wire to ground (or less likely, +V) and it has a bad connection or intermittent open that would take them all out together. That's the simplest explanation.

 

My rear left sided indicator bulb was burn out. Until I replaced the bulb my right side steering wheel buttons did not work, or only work intermittently as you described.
Check under the radio for a large plastic magnet (like the one stack on the fridge) this caused my display to fail, and was a “gift”from the dealer. My display is still faulty.



iPad ?

 

Despite the fantastical claim that there is a relationship between the rear left-side indicator bulb and the right-side steering wheel buttons, it is more likely to be the steering wheel spiral cable that is damaged and needs to be replaced. Buy the more expensive OEM cable (shop online for a competitive price) as the cheap knock-offs don't seem to last. Unless your idea of fun is replacing the spiral cable annualy.

To fix the bezel buttons on the MFD might require that you find a working second-hand unit and replace the MFD. Get the part number off the back of the MFD and buy this exact model when you buy the replacement.

 

I think the button bezel may be separately replaceable. I bought a Gen 2 from a rebuilder once and on the day I picked it up, it had a nav unit under the seat but a non-nav MFD, and when I asked about that it went back in the bay for a few minutes and came out with the right MFD model but a funky button bezel, and then got a different bezel popped in. The process kind of reminded me of the Vendaface.