I have a 1993 Dodge Dynasty, which was somewhat jerry-rigged when I got it. The previous owner had modified the A/C clutch motor wiring and had wired it into a toggle switch on the dash. The audio headunit (just stock) does not work at all. I got an audio connector pinout from the net, and did some testing. There is no power from the 12v ignition pin but there is 12v from the 12v memory pin. These are the only two pins relavent. The 12v memory on the pinout sheet is labelled 12v CONSTANT and the 12v ignition is labelled SWITCHED. What does that mean. Now if you were wondering why I mentioned the A/C I was told the guy that was messing around with it cut a wrong wire somewhere that caused the audio to stop working. Any ideas where that would be? All the fuses are ok. Is there any way to get car wiring schematics. Even something close so that I could locate possible sources of the problem.

Thanks for your help

 

The lead marked as 12V CONSTANT simply means that this lead is connected direct to a fused battery source, without passing through any switches. It is used for supplying the memory circuits -- tuner presets, tone, balance, etc. -- and the clock. The lead marked 12V SWITCHED is just that -- it is another +12V souce that first passes through the keyswitch. This lead should go high when the keyswitch is placed in either the IGN (ON) or ACC (ACCESSORY) positions.

You have answered two of your own questions with a single statement -- "There is no power from the 12v ignition pin..." -- that is why the system is not working, and it is also most likely the wire that was cut!

As to sources for vehicle schematics -- of course the factory service manuals will have them, but that is a fairly expensive way to go. However, for under $20.00 at most any parts store, you can get a Hayne's or Chilton's manual for that vehicle. Either of them will have the vehicle wiring diagrams.

 

There are many problems associated with this. there are acouple pressure switches on the air conditioning unit that wont let the compressor turn on b/c the pressure is either too high or too low. The connection from the A/C controls went bad in my friend's Silverado, so he has a switch rigged up too. I would try to use it as little as possible, or have it looked over by a professional.


It just means that when the key is in the off position there is no voltage on that wire, when you turn the key to the run or acc. position there will be voltage on that wire.

Check for voltage at the radio fuse (be sure to turn the key to the run or accesory position), that wire he cut could have been before the fuse. So you dont have any voltage. if it is that wire he cut, try to find it and splice it back together. As for the schematics, many repair manuals will have them. They're sold at your local auto store.

__________________
Jeff
To the optimist, the glass is half full.
To the pessimist, the glass is half empty.
To the engineer, the glass is twice as big as it needs to be.

 

I finally found time to do some testing and I found that the head unit is getting power. The fuses are all good. I was talking to a car guy I know and he said the units in some cars have some kind of protection thing. If the unit doesn't get power for a long time a code has to be entered to "reactivate" the unit. I've never heard of anything like this, but do you guys know how this works? Thanks

 

There are factory and aftermarket radios that do have a security feature like this. When they are first installed you enter a 3 or 4 digit number using the preset station buttons, and this becomes the security code for the radio. If the power is removed for more than a short period of time, they will not operate unitl this code is re-entered. It is to help prevent theft, since the radio will not work without the code, and if it is stolen, the power will be disconnected. Most times the only way to reset the code is either at the cars dealership, or place of purchase with proof of ownership.

There are aftermarket amplifiers like this also, same function, but the code is entered by way of a type of "morse-code" using a small connector, or there is a 1/8" headphone jack or similar that conects to a small device with a 2-wire serial EEPROM in it. The EEPROM stores a serial number for the equipment, and it is checked on power up, if its not there, the amp won't turn on. This small device is mounted somewhere very inaccessable in the car, hard to find.

If your car uses this security feature in the radio, a dealership is likely the only way to get the code reset.

 

My factory radio had this feature. It had markings about the antitheft feature written on the front of it so you could clearly see it had a theftlock feature. It would also tell you that it was in security mode and that you needed to enter the code.

Is it possible that the radio is bad?

__________________
Jeff
To the optimist, the glass is half full.
To the pessimist, the glass is half empty.
To the engineer, the glass is twice as big as it needs to be.

 

I am starting to think that the radio is bad. I don't know how to find out w/o taking it to a dealer. There is no marking indicating the theftlock feature and no "code prompt" screen is displayed so I doubt it has this feature.