Radio has no power
 

I am honored to now be a part of the Corvette faithful, having just purchased my first Vette, a 1993 Torch Red on red auto. There are a multitude of gremlins but I'll start with the radio doesn't power on. Yes I have checked the fuses, all were good. Any ideas? Also the ECC only blows "defrost". Any relation to some sort of issue behind the center stack?

Bose?

Sorry, yes it has the Bose cd and cassette stereo.

I assume it's a Bose gold system.
Does the LCD display on the radio light up at all? If it does I assume there's no sound.
If you push the volume control knob with the radio turned off, does it display the time?
Fuses to check: # 4 & #40

OK so this is kind of a stupid question, look in the compartment behind the passenger seat. Remove the plastic pull out box and look to the left. Do you see a (silver) box tied down with a cable on it. I just want to make sure it's there.

Do you have a manual or automatic A/C system?
Check the 3 hose check valve under the plastic cover on the right side of the engine above the fuel injectors. The cover just pulls up and off (gently and slowly). Look at the check valve for any cracks and breaks.

There are no lights,nor time displayed on radio. Volume up or down does nothing. I have checked all the fuses on the passenger side and all were good. Are there different types of Bose systems? The ac is auto but seems to only have 1 fan speed, and one direction..defrost. Not sure if compressor is coming on or not. By right side I assume you mean the passengers side of engine?

all interior lights work?

When you turn on the radio, does the antenna come up or make any noise at all?

You need to find out if there is any voltage on fuse 40 (5Amp) by removing the fuse and testing each side and verify one terminal has voltage with the key on. Also check the fuse with an ohm meter, don’t just look at it. I would suggest to try a tape or CD but you may have a problem getting it out so you may want to steer clear of that for the moment. Depending on your voltage check results will determine to look forward or back.

Did you verify that there is a CDM chassis in the compartment behind the passenger?

A/C - I interpreted the problem as a vent problem where the buttons worked and there might be a vacuum issue. But after your last information says the buttons don’t change setting as you depress on then as so the fan speed also. Sounds like bad contacts on the buttons in the control head. The control head can be disassembled easily and contacts for the buttons cleaned. There are lots of threads on how to do this as well as videos if that's your problem.

I verified every fuse in the car with a multimeter, all checked out. Hopefully this weekend I can check for the voltage on that fuse. The antenna does nothing as well, be it noise or movement. I don't think a cd or tape would do anything being as how there is no power; wouldn't draw either in.

Maxi fuse #1 in fuse block 1 under the hood feeds several fuses in the fuse box that is in the car.

Fuse 40 also feeds the PKE system and the PKE light on the dash (lower left) that would flash when key is turned to ON. So if you can verify the PKE has any form of life, then fuse 40 is working and has power to it.

In addition, the 12 volt bus from maxi fuse 1 feeds (fuse 38) the courtesy lamps, chime box and lights on the instrument cluster. If these things are working then maxi fuse #1 is OK.

Ok, so I have finally purchased my 93 and can now fully troubleshoot. There is indeed a silver box in the passenger compartment. I retested the hvac controls. All buttons light up as applicable but air is only diverted to defrost. Fan speed changes accordingly. Radio knob being turned or pushed does nothing, as does the antenna. Fuse #40 is good. Haven't checked for voltage on the pins yet. Won't stop raining. What type of fuses are those in the passenger fuse panel? I bought minis, too small, and then normal size too big.

No Matter what I think at this point you will be pulling the dash apart. Since all the fuses seem to check out I think it's time to delve deeper. I would double check that Box in the compartment behind the passenger seat. Make sure all the connections are seated. When I pulled that box out it killed my Radio completely... Nothing...

This site is invaluable for help with the stereo Systems:
http://www.carstereohelp.com/corvette.htm

However, the bulk of your information will come from a link on that site to this page:
http://www.carstereoremoval.com/htm/...ette90_96P.htm

Soak up all the info because it will confirm what you may want to do as a next step. (i.e. 3rd party system replacement vs repair)

My 95 actually had a non-bose system that was starting to sound a bit funky... (Speaker degradation and rheostats getting old) Thus I decided to box up the old system and get a Newer Pioneer system with Bluetooth and replace all four speakers.

As far as your stuck on defrost. If memory serves I think if the controller unit goes bad it's supposed to have a fail safe and go only to defrost for safety purposes. Basically GM assumes you might live in a wintery climate and need defrost to un-fog the windows. It could be as simple as cleaning up the control unit.

Check out this video for getting to the unit and full service:

Good Luck! Let us know how it goes...

Check out the 3 hose check valve on the right side of the engine on top under the plastic cover for breaks and cracks. If you lose vacuum, you can't control the vents as vent doors are actually vacuum activated. A defective check valve is common problem. Lack of vacuum might also affect the cruise. Also any vacuum line to the cruise or anywhere with a big enough leak will give similar symptoms.

If the vacuum is all good, then the programmer could be the problem which is not common. Hopefully we don’t have to go there, a real pain to work on with the vacuum relays electrically controlled.

Turns out that I am missing that 3 way check valve. Picking one up today. That should fix the vent control issue. The control center seems to be working just fine: all buttons light up in their respective position. As for the radio, I checked the voltage behind fuse 40, and am getting 10.8 volts. I am guessing there is an issue then, with the CDM?

Considering you just go the car and there are various issues including the check valve missing. Who knows what was done to the car by the previous owner "Joe butcher".

Don’t know is something is missing, disconnected or cut. There is more that can be checked before you throw money at it. There is interaction of voltages between CDM and control head.

The control head signals the CDM to turn on. Then the CDM feeds additional voltages back to the control head. The control head and CDM has its own independent constant voltage (12v) feed. The CDM has also a switchable voltage from turning the key to the ON position.

By pushing the volume control it should show the time, a basic function which does not work. A pain but I would pull out the radio head and make sure it's connected and wires look OK. Inspect the wires and connector pins at the CDM. Having a basic FSM schematic to take voltages would be a great help.

If all fails I would consider then sending the CDM out for repair.

Thanks pcolt94 for the help. I installed the check valve and now the climate control is working as it should, minus a low freon charge. I have both a Haynes and Chilton manual coming today which should help.

Those manuals are light weight information and non specific as it covers a range of years. Every C4 is different with electrical, vacuum, control circuits and many other things. Yes some years are more similar than others like 92-96 are similar but still have many differences from year to year.

If you are going to be serious about supporting and working on the car and looking for a specific point to measure or a part, the FSM is the only way to go. It also explains much of theory of operation of systems, troubleshooting flow charts, what causes error codes and much more specific and general information about the car.

where can I get a Field Service Manual?

Here is a place you could get the FSM. I purchased mine through the parts for sale section on this site for a bit less than that.

If you truly are getting 10.8 volts on the fuse it could be related to your issue. I am not sure about the CDM or the head unit, but the Bose amplifiers I have tested don't seem to come on until 11.0 or 11.1 volts. What voltage do you have at the battery?

12.4 off, 13.9 when running

:iagree:
I checked with Helm the maker of the books. They do not carry the 93 anymore new, don’t know why, they have older and newer years, go figure.. I paid $116 10 years ago so you can figure what a good price would be today. Used books are fine and for $139 I would grab it, not many around. But the info in the books are priceless.