Radio issue

[pasvorto1]

I have an Alpine radio in my 78. It has a power antenna. I tore the console apart to fix the reverse lockout. I got that fixed and got everything back together again. Now I have a radio problem. It is eating 3A fuses like M&Ms.

There is a red wire that comes from the power source to a 3A in-line fuse and on to the radio. Another wire comes from the back of the radio to a 3A in-line fuse and off to a unit under back of the emergency brake. From this unit come the wires that go to the antenna motor. So, the radio wires go into the top connector and the motor wires come out the bottom connector.

I have checked all the wires for bare spots. None found. I thought that maybe the neutral and reverse lights were getting caught on the shifter mechanism (it is an automatic). So I tore it all apart again and ran the wires under the shifter plate, out of the way. That probably needed to be done, but that wasn't it.

If I have a fuse in both places, when I turn on the radio, one of the 2 fuses immediately blows. I put a 10A fuse in the antenna unit, as a test. The antenna went about 3/4 of the way up before blowing the 3A to the radio. So, I know all the antenna stuff works, it is just drawing somewhere between 3 and 10 amps. Why? It never used to.

I have 2 ideas. One is that there is STILL a bare spot somewhere and I just haven't located it, or the other is that the unit between the antenna fuse and the antenna motor just happened to go bad at this inopportune time.

Is that unit a transformer or a relay? I have no idea. However, when I turn the radio off, it makes a popping sound. There is nothing in my 1978 Corvette Assembly Manual that even makes reference to a power antenna.

Each time I go into AutoZone, I cause a laugh and they head right for the fuses. How embarrasing. Help a guy out.

 

[wishuwerehere82]

Pasvorto1,

Either you have a short in the wire between the fusebox and the motor, or you have a short in the motor itself.

First, unplug the harness for the electric motor that connects behind the driver's side rear speaker. Then read the voltage between the yellow wire and the black wire and the voltage between the green wire and the black wire. As you turn on the radio one of them should read +12V and the other should read 0V. When you turn the radio off the voltages should flip between the green and yellow wires. One is to put the antenna up, and one is to pull it down.
If the fuse still blows with the motor disconnected, you have a short to ground somewhere in the harness before the motor.

Now if all that checks out and no fuses blow, then the problem is in the motor itself. My roommate back in the 70's was the electrician on the power antenna line at Delco so I know a lot about what kind of problems they had geting the things to work when they were new!

The motors are 12V DC motors and when they wear the commutators smear the copper from the commutator contacts until the gap between them shorts out and causes a direct connection between the brushes. That will blow your fuses for sure.
The motors are riveted together so you will have to drill out the rivets to get the case apart to check it out.
Once the rivets are removed the case comes apart with the removal of about 6 metal clips that hold the case together.
The motor housing is in two halves that fit together.
Once the case is separated, you will see the motor with two spring loaded carbon brushes on either side of the commutator. Pull the brushes back into the sleeves they come out of and tie them back with a piece of dental floss so that they don't spring out when you remove the motor shaft.
If the commutator is shorted the copper will be burnt and lots of spots between the commutators will show signs of arcing. You can clean the surface up with a fine grit sandpaper(800-1000 grit) and separate the commutator shorts with a razor blade in the gaps between them.
Put it all back together and replace the rivets with screws and nuts.

The box you are referring to is a relay that switches the voltage between the two wires until the antenna is up or down. Not likely that it is shorted.

 

[pasvorto]

Just to make things weirder... The boss decided that the beast has been torn apart long enough. We can live without an antenna for a while. So, I took the 3A fuse out of the antenna connection. That should kill that circuit. We went out for supper. The radio worked fine. We came out from eating. I turned on the radio. Nothing. The fuse must have blown. So, I can only assume it must not be in the antenna circuit because that was disabled and yet the radio fuse blew. Arghhhhh....

I think I am going to have to pull the radio out and see if any wires got damaged when I took the console top plate off. That's all I can think of. Wires up behind the radio, where I can't see them are bad, or the radio itself is bad.

I hate electronics.... :-(

Still open to suggestions. I certainly don't want to take it to AudioDesigns and pay them a king's ransom to find the problem.

 

[jdp6000]

Sounds like an aftermarket wire hook up. From your post is appears you can see all the new wiring and there are no bare spots. If your car had a power antenna from the factor there should be another wire in the harness for it. It sounds like the factory wire may have been bypassed. There should be a larger harness under your console. maybe you disturbed a cut wire within it that once feed the power antenna. Keep in mind I have an 82 and am assuming there are similarities.

the other possibility is the ground wire that comes off the actual antenna and attaches to the frame above the rear driverside exhaust.

Jim

 

[pasvorto1]

Well, the fact that it happened after I had the console moved out of my way, makes me think I must have disturbed something. I may take the radio out and see if I caused a problem in the rear of the radio, that I can't see with it installed.

 

[pasvorto]

Another weird time with the radio. I went for a drive yesterday. I truned ont he radio (force of habit) and it worked just fine. No antenna (I have the fuse removed). I stopped at a local cruising spot for a few hours. Left. Radio still working fine. I got home and turned off the car. No courtesy light!! Arghhh


And I thought my old MG Midget had screwy electronics!

 

[jdp6000]

Someone has spliced into your harness. Its the only thing that makes sense. Check for wireing that looks to be added on. Remove them and return the car to stock. It sounds like the source of your problems may be the radio. Where does it draw its power from?

Re the courtesy lights...was it just the fuse???

Jim

 

[pasvorto]

I may very well have blown the courtesy light fuse when I was eating fuses testing the antenna. I will check later. it was dark then.

The radio is aftermarket. Has always worked. Power comes froma red wire (I assume going to the fuse panel). I think I need to pull the radio and make sure I have not strectched any wires when I removed the console. That's the only explanation I can come up with. I can't see any "open" spots in the console, but I can't see what is behind the radio.

 

[pasvorto1]

Just keeps getting more interesting....

The in-line fuse is missing for the antenna. I removed it. I did find that the fuse for the courtesy light was blown. I replaced it. Guess what? The radio and the antenna work just fine now, even though the 3A in-line fuse is still out...

:W

 

[jdp6000]

Your going to have to pull the radio. Power is usually supplied by the harness for all these things. Speakers are through the harness as well. Since its after market they have probably not used the harness plug(s) and spliced wires in. You probably moved something. I don't know what kind of radio you have so I can say if it will simply pull out. You will have to figure this out.

What you can do is remove the center cluster along with the radio still mounted. One way or the other you'll need to get to the harness behind the radio to determine whats wrong.

Jim