tim1

I put my GPS in the Vette the other day and while waiting for it to aquire sattelites the radio and GPS both shut off. I checked the fuses and found the radio fuse blew, so I unplugged the GPS changed it out as soon a I turned the key on it blew the radio fuse again. I am thinking there is a dead shorted wire between the radio wire and the cigaette lither wires. Anyone have any other ideas? Or have a wiring diagram for these underdash wires so I can try to locate the problem? Thanks for all your help.

WVZR-1

It might help if you mentioned THE YEAR - in most OE applications the radio/lighter aren't related. Factory radio?

tim1

Sorry, its a 93 and the factory radio is installed.

tim1

Lets see if the weekend crew can help me out here.

tim1

Well I hate to bring up a very old post but I still have not gotten this fixed. Today I started taking things apart, unhooked the cigerette lighter and removed the fuze for it. I then put in a new 5 amp fuse for the radio, turned on the key and the radio came on for about 5 seconds and blew the radio fuze. I suspect it is the main ground for the radio system. Can anyone point me to the grounding location for the radio system so I can check to see if it is actually grounding? Or anyone have something else I might need to check?

Bandit's C4

Am looking up those details for you... here are a few diagrams to look over.

Cruisinfanatic

does it blow with radio off? I've had a couple over the years that did this

tim1

I have not tried it with the radio off but I can tomorrow. Looking at the ground diagrams I may have a lot of checking, but the radio has not worked for over a year now so what do I have to loose.

tim1

I removed the stereo today and nobody in this town can hook it up to check the radio. So I put in a new fuse with no radio installed and turn on the ignition, the fuse did not blow which leads me to believe that the radio has given up the ghost. Time to try and find another factory Bose radio I guess.

csthews

Just curious if you ever tried it with the radio installed, but turned off as suggested. Could be the radio, or it was wired up incorrectly which would blow the fuse the moment you turned the key to accessory.

tim1

Yes I tried with the radio off, and it did not blow the fuse. The radio and all the wiring is from the factory install it has never been removed or rewired.

csthews

Ok,

So I'm approaching this from the standpoint of a 95 with Bose Stereo, but I think it also applies to the 93 based on the above pics. First, the radio is divided into 2 units, a control unit and a receiver. Which fuse keeps blowing on you, the radio ignition fuse or the radio battery fuse? If it is the ignition fuse, the issue is more than likely not in the control/head unit that you removed, but rather in the receiver, receiver wiring, speaker amps (if bose), power antenna, etc. From the above diagram, the ingition fuse only feeds the receiver. The reciever power circuit is closed in via a relay which is controlled by the head unit (i.e. turn on the head unit, the contacts on the relay close and complete the circuit.). So, if you turn on the ignition switch with the control unit either off or removed, no power will be fed into the receiver. This only verifies the wiring from the ignition block to the reciever.

With that said, if you dont have a good troubleshooting guide (i.e. fsm) then you can try to locate the issue by process of elimination. You can disconnect the power antenna, and especially if you have a bose system, power to the speakers. Be careful to not leave any connectors exposed of course. And see if the fuse blows again.

tim1

Yes it has a control head and receiver. The fuse that keeps blowing is the 5 amp batt fuse. So you are saying to reinstall the head unit, and start by disconecting the antenna, and see if it blows the fuse. If it does blow then disconnect one speaker at a time and turn the ignition on and see if it blows the fuse. Continue to do this until I find which speaker or amp is the culprit. I hope I got that correct, hope you get a chance to post early this morning so I can get after the probelm today. Thanks for your insight.

HlhnEast

I think that the antennae motor may be bad as well. It would be a more likely culprit seems like. That would be another reason why when the radio is off, the fuse doesnt blow.

csthews

I would bet on the antenna, but since it is the battery fuse that keeps blowing, I would:
1. reconnect everything, pull the radio ignition fuse, then power up the head unit. If the fuse doesn't blow, it kinda rules out the head unit and vice versa.

2. pull power from everything powered by the reciever which would be the antenna motor and, if you have bose, the speakers. Power the system up again to rule out the reciever.

3. reconnect the individual components starting with the power antenna until something blows the fuse. I know you know this, but as a disclaimer if have to say, power off the system and turn off the ignition before disconnecting/reconnecting anything.

4. you could just skip steps 1 & 2 and just pull power to the antenna only. If the fuse doesn't blow, you got it. If it does, then go back to step 1.

Good luck

csthews

I tend to get tunnel vision when diagnosing issues, so I re-read your OP and realized that I might be leading you on a wild goose chase. It appears that the fuse was ok until you plugged the GPS into the cigarette lighter. And with the GPS still plugged in, the fuse blew immediately when you turned on the ignition switch. Before you waste your time doing all of this, let me go back to your original request and see if there is anything in common between the cigarette lighter and the radio.

I don't see anything in common between the cigarette lighter and the radio. Different fuses and different grounds. So, did you check the cigarette lighter fuse as well? I can't see how blowing the radio fuse will kill power to the cigarette lighter.

VikingTrad3r

just going to chime in fwiw. i had an issue with my 87 (i know yours is late model) where when i plugged anything in it would blow fuse. the pressure of my charger in the socket caused the cig lighter to short out, allowing the full 12v to flow baby and blew the fuse. the cylinder that makes up the cig lighter unit was turned enough so that when something was inserted, it shorted. tough to explain but maybe your issue as well.

my cig lighter and radio is on same fuse.

good luck with your gremlin!!

tim1

Can anyone tell me how to test the CDM? I think that is the culprit.

csthews

What is a CDM?

tim1

Itis the am/fm tuner located behind the passenger seat.