Need help diagnosing potential radio/sunroof relay problem

[idealcheese]

The aftermarket Sony stereo cassette in my 1984 stopped working (no sound, tape stopped spinning, but clock still worked) and I assumed it had just bit the dust. I sourced a new old stock similar model on eBay and after connecting the power and antenna wires, plugged it in to the new radio. The clock comes on, but the antenna doesn't lift and the tape player doesn't spin. Same problem! Apparently it's probably the radio/sunroof relay (I verified it's not a fuse). I've tested that the sunroof works correctly (tilts up when the key is turned, retracts arms when they key is in off position). Now I need to verify that just the radio pin of the relay has failed (or whatever the terminology is). How do I do this? I have a multimeter but don't have a 12V power supply that isn't a car battery. Thanks in advance for any help!

[dr bob]

Your symptom says you are missing the "always on" power source.

The detail:
There are typically two power connections for these aftermarket radios. One is 'always hot', fused from battery positive circuit 30 then again in the fused power lead at the radio itself. . The other gets a 'trigger' from accessory on the ignition switch (via a separate inline fuse), and turns on the display clock and such. There's a potential (sorry...) for several fuses to be involved, when you consider the places where power was tapped from the car, and again in the fused power wires supplied with the radio itself. Most of these single-DIN radios slide in and out of a sleeve in the dash. While it's certainly possible to test for voltage and ground in that plug inside, the best option may be to remove that sleeve and test the fuses plus power to that socket.

[idealcheese]

Thanks, Dr Bob! I have identified the 2 wires for the always hot and switched power to the radio (yellow and red). Can I test directly from these without having to take anything else apart? When you say "remove that sleeve and test the fuses plus power to that socket" I'm afraid I need more 'splaining. (Relative noob here.) The radio is currently out, and so far only the 2 power wires are connected to the new harness. Can you outline the next steps? I appreciate your help so much, thank you!
-Alison

[944er]

Your symptom says you are missing the "always on" power source.

No, he has the always on power, that is why his clock works. He is missing the switched power through fuse 7 and the radio/sunroof relay to his head unit.

[idealcheese]

Thanks 944er (I'm a she actually). You are correct, the always on power works, it's the switched power that isn't working. I checked the fuses on the wires from the harness and they are good. I checked from fuse panel to ground at fuses 7 and 8, and both are showing 12V. So it seems likely to be the relay that has partially failed (the sunroof still works). Unfortunately they are no longer available!