: electrical problem on a 79 coupe



79coupedevile
07-27-13, 10:18 PM
I have a 1979 coupe deville, while the cars on and im listening to the radio if I turn the interior lights on or open the door the radio goes out the clock resets and so do the radio stations, ive owned the car for the last 5 years and is completely 100 percent stock the electrical issue just happened out of nowhere about a year ago I need some help I cant figure out what is causing this to happen

cadillac kevin
07-27-13, 11:46 PM
I have a 1979 coupe deville, while the cars on and im listening to the radio if I turn the interior lights on or open the door the radio goes out the clock resets and so do the radio stations, ive owned the car for the last 5 years and is completely 100 percent stock the electrical issue just happened out of nowhere about a year ago I need some help I cant figure out what is causing this to happen

My guess is it is somehow cutting off power to the radios constant power (memory). Maybe someone installed then removed an aftermarket radio at one point and messed up the wiring harness. I'd remove the radio bezel and put a mulitmeter or test light on the memory wire and see if it loses power when you turn on the interior lights. If no, I'd guess a fault in the radio electronics. It is a weird issue.

lacville78
07-27-13, 11:49 PM
I had these symptoms when my alternator was going out, although the generator light was on too.

1980coupe
07-28-13, 01:57 AM
So the radio is stock?

The Ape Man
07-28-13, 12:20 PM
The body feed fuse that feeds the interior lamps also feeds the radio keep alive memory. That is a clue. If you can't figure it out a diode in series with the radio's keep alive feed cathode end toward radio with a fresh electrolytic cap across the radio side would fill the void. 1N5408 diode, 2200 Uf @ 25 VOLT CAP.

79coupedevile
07-28-13, 02:41 PM
the body feed fuse would be where in the car? and the car has the stock radio

The Ape Man
07-28-13, 06:33 PM
the body feed fuse would be where in the car? and the car has the stock radio

Main fuse panel forward of emergency brake. Should say BODY near fuse. The owner's manual has info too for another check.

1980coupe
07-29-13, 12:28 AM
I know there is another fuse, but I could be wrong since I don't have with me the diagram of fuses. Check at radio for any possible interference
with the main wires to the radio, orange is constant 12v and yellow is switched 12v..

carnut
07-29-13, 03:45 PM
I will bet the BODY fuse is blown. Usually caused by loose cell phone chargers sparking as they are inserted or removed or tin foil, dimes etc in a lighter socket.

79coupedevile
08-07-13, 08:02 PM
the body fuse is fine, there was a after market radio installed but it started happening with it installed 2 to 3 years later...

The Ape Man
08-07-13, 08:25 PM
Another possibility would be a marginal ground connection to the radio. If the chassis of the radio floats too high above ground voltage wise it can dump the presets. Some folks only have the ground provided by the antenna lead which can be marginal.

nyshark
08-11-13, 01:48 PM
I think it has something to do with the dimmer system , The low voltage feeding the radio when you turn interior lighting on forces the low voltage trip out to engage in some after market radios . I just ran a direct feed from positive battery terminal with an inline fuse it has been okay since doing this .