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Okay, this is the radio in my '85 MR2 not my Chevelle, but if it wasn't for the MR2 I'd have to drive my Chevelle in the winter salt!

Anyway, this radio has been acting up for well over a year. The volume knob is also the on/off button. You push the knob to turn it on or off. Over a year ago it began turning itself off randomly. Most of the time I could simply turn it back on and I'd be fine. It would have erased all the station presets so it was doing more than turning itself off. Eventually I was not able to turn it back on, it would click on briefly but would not stay on. I took it to a local repair shop. They said due to the brand (OEM Toyota, I think it was Panasonic or Toshiba) they could only send it to the factory for repairs.

The bill was $185. I could have bought something new for that! Anyway, it was the original equipment unit, fit in the dash and worked and sounded great when it worked so I'd just be happy if it worked. Well, it lasted about 3 days and the same problems cropped up now and then. It no longer turned off while in use but did so overnight almost every night and every night it wiped the presets. Irritating to be true, but at least I could still listen to the news on the way to and from work.

Fast forward to this summer. Now it is beginning to turn off while in use and won't come back on for days at a time. I found out I got a 1 year warranty on the work from the so-called repairs the factory did. I took it back in, they shipped it to the factory and the factory sent it back claiming they could find no problems. I reinstalled the unit and it failed before I left the parking lot.

The local shop could only offer that it must then be an issue in the wiring in the car. That is total BS because when the radio won't work, won't even come on, the cassette player will still work. There is only one power wire for the unit as a whole. The lights on the unit work at any time. Power to the unit itself is not an issue. They said a short circuit in some of the speaker wires could cause such a problem, but then wouldn't it also occur when playing a cassette? The cassette player turns on when a cassette is inserted and works independently of the on/off switch. I think that in itself proves it is the on/off switch in the radio itself.

I paid money to have this thing repaired. It has not been repaired. Whether they can recognize the problem when they have it does not mean it does not have a problem. How can I convince them? Why didn't they just replace the power switch in the event I was right? I can demonstrate the unit's failure to the local shop but that does nothing to convince the factory who supposedly did the evaluation.

Solutions to prove my point:

-could I run an independent power line with a switch and a fuse directly from the battery to see if the issue still exists? Would that prove anything?

-could I disconnect the speaker connections and the antenna connections to see if the power will at least come on and stay on?

Since I honestly don't believe it has anything to do with the power supply to the unit I hesitate to even bother, but is there anything I can do to improve the power connection? The spade connector looks like new.
 

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If there is only one power lead, into the unit, then the deck must be wired up to an “always hot” lead. That is, the radio will work with the key off.
That being the case, power comes into the unit and goes to 3 basic places.
1, The memory circuit that maintains the presets.
2, The switch that runs the radio.
3, The switch that turns on the cassette.
As you stated you never loose power to cassette switch. I assume it plays so the motor and the internal amplifier circuits are getting power. The amplifier(s) will be the same amplifier as the radio uses so I agree that the speakers aren’t an issue.
Without looking at a schematic, I’m going to assume that the memory circuit has it’s own power supply.
If I was troubleshooting this, I wouldn’t blame the switch. I would look at the internal wiring that feeds the above 3 items and see why 1 & 2 are loosing power. Maybe there’s some common point with a poor solder joint.
 

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Discussion Starter #3
The unit is switched at the ignition switch, in other words it turns off when I turn off the key. Well, the radio/cassette turns off but it would have to have some remaining power to maintain the presets wouldn't it? Perhaps the power supply internal to the unit is computerized? Or perhaps a secondary power supply is entering via the multi-plug which includes the speaker leads. I assumed all the wires on that plug are speaker leads, perhaps they are not. The wiring schematics in the shop manual do not show details when it comes to the radio for some reason but I'll look them over again.

The circuit boards are so jam packed with tiny circuits I wouldn't even know where to look for a poor solder joint. I have looked but I've no idea WHERE to look. I'll have to trace where the power supply unit feeds power to the rest of the unit and see if I see any obvious problems. You'd think even a factory technician could do the same thing........
 

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Well, that changes a couple of things. If the radio does turn off with the key then it has to have a separate line that maintains the radio presets. It doesn’t use an internal battery as back-up power. It uses another wire tied to a terminal that always has 12 volts. That’s the normal way they work.
Now you have 2 problems.
1, The presets get cleared.
2, The radio goes out..
How intermittent is the preset problem? Does it go out once a week or sooner? I hate intermittent problems. They are the worst to chase.
 

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If you just want to troubleshoot to see if the power is cutting out before or after it gets to the radio, you can just rig a wire up to the "spade connector" you speak of and run it to a cheap little radio shack LED or bulb.

This should at least tell you if you have a short in the wiring harness or in the radio.

If its the radio, I would vote for getting a cheap aftermarket radio and installation kit from best buy (or equiv.) rather than waste any more time getting the stock fixed.

I had a thunderbird a few years ago and once the radio went out and I started sending the radio in to be "fixed" it would continue to fail regularly (usually right about the time the warranty was up).
 

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Discussion Starter #6
Originally posted by John_Muha:

How intermittent is the preset problem? Does it go out once a week or sooner? I hate intermittent problems. They are the worst to chase.
When it is working as good as it ever does lately it loses the presets every single night. Right now, the radio won't even turn on in the first place. The cassette still plays of course. At lunch today it turned on and lasted about 5 minutes. Since then it wouldn't turn on. At some point it will come back and work for a while. Each time it dies I takes the presets with it. It has been quite some time since the presets lasted overnight.
 

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Charles’ idea is a great way to monitor the line if you are driving in the car. I’d use the LED here because they don’t get hot. Almost need to put the LED up in an area where you can see it while you are driving without looking down.
*Thought s of suggesting to Rich about hanging purple ones on his window squirters.*
Also you could try your original idea of another fused power line to the unit. I’d find the constant power line for the presets and tie that to known constant 12 volts. Might be worth a try.
Again without a schematic, I just pull ideas out of my ear. In the cassette mode the unit doesn’t use the tuner/receiver section. Maybe that section uses the same power supply that feeds the memory. If it’s as intermittent as you described the bench techs should have seen it.
 

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The repair shop that sent it in and has had to listen to me whine on about the problems encountered hooked me up with another company they do business with to do installs. I made an appointment for tomorrow so we'll see what comes of that.
 

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It's these type of problems that make me glad I've been out of the consumer repair business for the last 15 years. At least $75,000 cameras are meant to be repaired. ;) My hair is grey enough!
 

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Discussion Starter #12
Of course it was working beautifully when I visited the installs guy today. At least he helped me determine which power feed runs the radio and presets part of the unit. Apparently it has a separate power source for the cassette which would explain why the cassette continues to work when the radio fails. Perhaps it IS the wiring in the car. Next time it fails I'll check that power lead with my multimeter and that will tell the real story.
 
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