Cavalier defogger troubleshooting?

With this 99 Cavalier, I've got a rear window defogger which just stopped working.
No voltage at the two terminals that clip on the glass. Resistance in the
heater, it's not open.
The 30 amp fuse is good, there's voltage on one side to ground.
When the fuse is pulled the push-button that turns on the heater will not light up, but when the fuse is installed the yellow lamp comes on but no action at the defogger.
Before I pull the cable bundles apart, is there any other place I should look? Maybe a relay? where?
TIA
Dave
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Dave L. wrote:

On mine (GM, but not Cavalier) - there's a relay on the firewall...
Ken
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Check each connector at the window to ground for 12 volts. If there is 12 volts the ground to the heater is open somewhere. I am looking at the 96 wiring diagram and the light is attached to the line out of the control assembly to the rear window, only connectors and wire between them The relay/timing circuit is part of the HVAC-A/C and rear defogger control assby behind the center dash. Don't know if the 99 is the same...

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