Hi fans. I've ridden in to save the day!
I'm not familiar with this radio model, but I can offer some suggestions. Since all radios now are full of computer controls, they are very susceptible to voltage spikes. It is possible for a circuit in a microprocessor to lock up and stop working. One of those driver circuits is for the brightness of the display, which varies as the dash lights are varied. (We used to do that with a simple and reliable dash rheostat). Another driver circuit runs the back-lighting for the buttons.
When the radio is unplugged, or has no voltage to it, the millions of transistors in the many integrated circuits turn on or off in random states when power is reapplied. Every one of those ICs has a "reset" circuit that sets all of those transistors to their starting points within the first few milliseconds, then its job is done until the radio loses power again, often months or years later. Since those reset circuits operate so infrequently and for such a short amount of time, failures are very rare.
My reason for sharing that wondrous information is to explain what could have happened here. If a voltage spike, or some other glitch, caused a circuit or part of an IC to lock up, it may be necessary for its reset circuit to put everything back to its starting point. In only a few cases that is accomplished by turning off the ignition switch or the radio's power switch. Most of the time those circuits are still powered up by the radio's memory 12 volt circuit. That is the circuit that maintains the station presets and clock memory when the ignition switch is off.
Removing and unplugging the radio, then reconnecting it will cause the reset circuits to do their thing. That will restore the dead function, until the cause of the failure occurs again. Keep in mind there could also simply be a bad solder connection inside the radio, but there wouldn't be much excitement in describing that.
All vehicles generate some voltage spikes, some much worse than others. It is the battery's job to dampen and absorb them, but as they age and the lead flakes off the plates, they lose their ability to do that. If you continue to have this problem, and the battery is fairly old, replace it before looking for more elusive, and possibly non-existent causes.
If voltage spikes is the issue here, there's two things to consider. The first is eliminating the cause of the spikes and the second is to address what is susceptible to them. If the radio has been identified as having common problems associated with voltage spikes, the engineers at Ford will have developed a modification. Every radio returned for repair will have that modification installed. You will receive a replacement that has that modification in it. If the problem can only be solved by some other modification in the vehicle, a service bulletin will be issued to the dealers. Those are very different than a recall notice. Service bulletins simply provide information to mechanics about problems with elusive solutions, so each mechanic doesn't have to go through all the time and trouble finding the cause.
To add another dimension to this sad story, Chrysler had a problem with their '92 Caravans. That was the first year they added a Body Computer to the dash gauges, power windows, and power locks, where a computer was never needed before. About every 5,000 miles those three systems went dead. The van could still be driven, but many owners figured out they could restore the functions by disconnecting the battery for a few seconds. When it was reconnected, the reset circuits in the Body Computer restarted everything working, but that wasn't a real or permanent fix. The fix outlined in the service manual included replacing all of up to a dozen relays with a specific part number. They were built by the supplier without the normal voltage spike suppression diode. Some of those relays were used in the power lock and power window circuits. When turned off, they developed abnormal voltage spikes, AND the Body Computers didn't have sufficient protection built in to ignore those spikes. The second part of the service bulletin specified also replacing the Body Computer. Recalls cover things related to safety or emissions, and once in a while, customer satisfaction. While this wasn't a recall, the manufacturer still usually supplied the parts for that customer satisfaction, and because it was a known design issue. The new relays addressed the cause, and the new Body Computer addressed the susceptibility.
So the bottom line is we don't know what caused the problem with your radio. If this happens again, remove the two radio fuses, then reinstall them, and see if the problem clears up. There is usually one fuse for the radio's power, and a second one for its memory. The memory circuit is always tied into some other circuit that is always live, and is rarely labelled as "radio memory". Most commonly it is tied in with the interior lights, but the horn, cigarette lighter, and even the brake light circuits have been used.
To add to the misery, many radios now have only the memory 12 volts. The radio is turned on by a digital signal from another computer when the ignition switch is turned on. If you can't find an appropriate fuse to remove, you may need to disconnect the battery for a minute. I hate to suggest that because a lot of cars today have computers that are designed to lock up and require a trip to the dealer to be unlocked. A lot of owners get stung by that when simply replacing an old battery. If you do this and you aren't sure what will happen, consider disconnecting the battery while sitting in the dealer's parking lot. That way a tow truck won't be needed. I haven't heard of this problem yet on Ford products, but it's worth mentioning.
The reason pulling fuses is better is if there is a bad solder connection inside the radio, it can be disturbed to the point of working again from the handling of removing it from the dash. Knowing what makes it start working can help in diagnosing the cause of the problem.
Friday, July 24th, 2020 AT 10:36 AM
(Merged)
