Help! Windows and radio issue.
04-21-2021, 01:59 AM
#1
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Help! Windows and radio issue. 99 Z28 is the car.
When I push the driver or passenger side button to roll down the window it kills the radio, then a few moments later the radio comes back on. Window will not roll down. Any other time the radio is fine and all just don't touch the button.
Any help on this?
If it is the bcm. where is it located?
When I push the driver or passenger side button to roll down the window it kills the radio, then a few moments later the radio comes back on. Window will not roll down. Any other time the radio is fine and all just don't touch the button.
Any help on this?
If it is the bcm. where is it located?
04-21-2021, 09:26 AM
#2
Everyone seems to want to blame the BCM for everything but in this case it is actually possible - although I doubt it. The only thing the windows and radio have in common is the Retained Accessory Power (RAP) circuit which powers them. That circuit is controlled by the BCM which provides power to them while the ignition is on and after it is switched off for a specified time or until a door is opened.
That common power source could lead one to conclude that the draw from the windows is more than the circuit can handle so the radio shuts off. The problem with that conclusion is that the power for the RAP circuit comes from a simple relay inside the BCM which switches from ignition/accy power from the ignition switch to battery power directly from a fusible link at the under hood junction box. There are no other components involved - it's a simple switch between two power sources so there is no restriction to current flow. The only possible way that the BCM is the problem is if that internal relay has worn or corroded contacts... something I've never seen.
That makes me think that there is some other cause of the problem. There are a number of things you could test if you have the necessary equipment - test light and/or multimeter at a minimum - and the time/interest to dig into it. Let us know if you have the equipment and want to try diagnosing it yourself and I'll post some steps for testing various components in a logical order.
That common power source could lead one to conclude that the draw from the windows is more than the circuit can handle so the radio shuts off. The problem with that conclusion is that the power for the RAP circuit comes from a simple relay inside the BCM which switches from ignition/accy power from the ignition switch to battery power directly from a fusible link at the under hood junction box. There are no other components involved - it's a simple switch between two power sources so there is no restriction to current flow. The only possible way that the BCM is the problem is if that internal relay has worn or corroded contacts... something I've never seen.
That makes me think that there is some other cause of the problem. There are a number of things you could test if you have the necessary equipment - test light and/or multimeter at a minimum - and the time/interest to dig into it. Let us know if you have the equipment and want to try diagnosing it yourself and I'll post some steps for testing various components in a logical order.
04-21-2021, 03:52 PM
#4
Okay, well the first thing I would suspect is the Windows circuit breaker in the fuse panel. Get yourself a 30A ATO blade fuse (a green plastic fuse the same size as the others in your fuse panel) and use it to replace the circuit breaker - it will plug right in. Those circuit breakers are known to cause all kinds of weird problems when they get old, including causing large current draws.
I'll post some more detailed troubleshooting steps when I have a chance to check my schematics after work.
I'll post some more detailed troubleshooting steps when I have a chance to check my schematics after work.
04-22-2021, 08:33 AM
#7
Okay, now that we know from your post in another thread that the windows have never worked since you got the car, I think we can eliminate the BCM as the cause. I suspect the window motors. I recommend removing the door trim panels and testing the window motors by directly applying power and ground to the two terminals on the motor, then reverse them to move the motor the other direction. I suspect you will find that the window will not move or that it will move only slowly and/or intermittently. That would be a clear indication that the motor needs to be replaced. These window motors are notorious for failing, especially when they're over 20 years old. Fortunately, they are quite inexpensive to replace if you do the work yourself (they range from $20 - $35 depending on brand). In fact, If you're going to be digging into the doors anyway, I'd probably just go ahead and replace them.
I'm never one to suggest throwing parts at a problem without doing diagnostic tests first but in this case I'm pretty sure it will solve your problem and, even if it doesn't, you're going to need to replace them in the not too distant future anyway.
I'm never one to suggest throwing parts at a problem without doing diagnostic tests first but in this case I'm pretty sure it will solve your problem and, even if it doesn't, you're going to need to replace them in the not too distant future anyway.