Good evening, I have a 2007 Prius and recently changed the MDF electric unit from a donor car. The new unit worked perfectly until today. As it was raining during the day, I had to turn on my headlights. The moment I turned on the headlights I noticed that the MDF screen went black. When I turned the headlights off the MDF screen turned on again. I also noticed that if I had the headlights on and turned the dash dimmer all the way to the on position (where it clicks) the MDF screen reactivated. Brief research indicated that this may be a glitch and gave some methods to reset the screen including disconnecting the 12v battery for 5 minutes and another method where I would turn the headlights on and off in a series. Another person indicated it may be how the unit is connected and suggested unplugging the unit and plugging it in again. Finally, another person indicated it is something in the internal electronics of the MDF unit. Any thoughts on this subject would be appreciated.
Dimmer dial questions were my first thought... Glad you addressed that... And MFD has same number of buttons? What year Prius was donor car? Also have you disconnected the 12v for a few minutes to go back to factory settings?
Thank you for taking the time to respond to my post. The MDF from the donor car had the same number of buttons that I had in my Prius. Also, the serial numbers were the same. The only difference is my car is a 2007 and the donor car was a 2008. I also have to note that the unit from the donor car had a junkyard name on the electronic part of the MDF so I know it was not original to that 2008 donor car. Regarding the battery, I have not done that test yet. I will do this tomorrow morning. Regarding the connections, I am waiting for replacement AC dash vents so I will check those connections and clean them when I do that work unless the factory reset (disconnect 12v battery) you mentioned works. Thank you again. I will post tomorrow and advised you what happens regarding the battery disconnect factory reset.
If donor car really did have its MFD replaced, my best guess is used MFD you got was installed in a car that had bad circuitry that damaged its original MFD and also damage replacement MFD that you acquired, but I've no legit basis to reference to make that claim. However if you have a friend or family member who has same vehicle with same MFD that would be the least expensive way to test. Perhaps @ChapmanF who has more experience than me on here has seen similar symptoms?
I'm still thinking illumination dimming. The MFD is built to change to a "night mode" display, dark background instead of light, whenever the taillights are turned on. It's not supposed to disappear! But it is supposed to go to a noticeably darker mode. That's related to the dimming of the other dash lights, but I don't think the dimmer control knob affects it. It's just a different display mode programmed into the MFD. The MFD's brightness and contrast adjustments might make a difference.
Good day, Well, I disconnected the 12v battery for 5 minutes and then reattached the battery. I turned on the headlights and the problem had disappeared. I thought.... great! Well, I drove the car about 5 miles and while at a stop light I decided to turn on the headlights again to insure the problem with the MDF was solved. Unfortunately, the issue reappeared. With the headlights on and the dash dimmer in the dimming mode, the MDF is totally black. When I push the dash dimmer to on, the MDF turns on again. I plan on putting in new ac vents and when I do that I will disconnect the MDF electrical connections and use an electronic connection spray cleaner to see if that helps.
Good afternoon, Thanks for the post! What happens is if I adjust the dimmer switch to on with the lights on, the MDF goes dark. When I slide the switch to the on position, the MDF turns on. Frankly I am unable to see the MDF at all when it turns dark. I will try looking at the MDF tonight to see what happens. The original MDF did not do this. The reason I got a replacement was because it had become so dark I could not see any of the controls anymore.
Right, the dimmer knob should have a click at the very top of its range, where all the dash lights should be as bright as possible and the MFD should stay in its 'day' mode. Any dimmer position below the click should let you adjust the brightness of most of the dash lights when the taillights are on, but the MFD just switches to its 'night' mode. Of course if you have replaced your Multi-Function Display with Medium-Density Fiberboard, that could also contribute to its being hard to see at night. The DISPlay button on the MFD should get you to a screen with brightness and contrast adjustments, I think.
