1994 Sierra Radio won’t power on

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MNorton

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I recently purchased a 1994 GMC Sierra C1500 Stepside. Really liking the truck and working on it.
my question is about the radio. I have the three part system that includes the casette equalizer. I think possibly the CDM may be bad. Will a defective CDM like bad capacitors keep the system from even powering on? I see reconditioned CDM for sale just hate to purchase if it may be the display head that is bad.
 
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DerekTheGreat

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After you verify the fuse for the radio is OK, I'd suspect the brainbox/CDM/Whatever. If only the display was bad, you'd be able to see life on the equalizer if there was any. 1994 is a unicorn year for those though, as it boasts better/larger heatsinks and slightly higher power output than the previous generation, so you'll want to make sure you replace it with another '94 brainbox. The updated units tolerate aftermarket speakers with their lower impedance better, which means much less flickering of the display lights.
 

MNorton

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Thanks for the information. I replaced the CDM with a reconditioned unit and have the same issue , nothing powers up! I checked and have switched 12 volts and constant 12 for memory just like the schematic says. I guess I’ll look for a display unit now, I just wanted to keep stock radio.
 

GoToGuy

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You might try " mnrelectronics.com " , M & R Electronics, Saginaw, Mich. They work a lot factory radios. It's an idea.
Good luck.
 

DerekTheGreat

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Thanks for the information. I replaced the CDM with a reconditioned unit and have the same issue , nothing powers up! I checked and have switched 12 volts and constant 12 for memory just like the schematic says. I guess I’ll look for a display unit now, I just wanted to keep stock radio.

That's a bummer. I am very skeptical of anything "reconditioned" or "rebuilt," are you sure that unit is any good and compatible with the equalizer? I'm fond of the stock radio too, went through pretty decent lengths to put one back in my truck. Are you sure all cables are present & plugged in? I forget now, but I want to say there is one which goes from the head unit to the equalizer. I could be wrong, but I'd suspect that if the display was dead in your head unit, the equalizer's display would still work as would all the other buttons. When I had issues with the first CDM I put in my truck, the display froze and none of the buttons were responsive. Replaced the CDM and it's been working fine ever since..
 
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