92 PAU rear defroster

I have a 1992 Park Avenue Ultra with the rear defroster tripping out prior to normal 10 min switch time-out.
Wiring, relays and switches have been checked.
Does anyone have an Ohm value for the grid in the rear glass?

What is a grid ohm? I used an ohm meter to check my lines. My defrost was cutting off also, I couldn't figure it out till I removed the rear side covers that pop on and off by the rear window, I then found the wire leading to the window had worn the insulation off and was contacting the metal lip. The cover looked to be putting pressure on the wire against the metal lip. Don't know if this is your problem but it wouldn't hurt to check. I repaired the wire and problem solved. This is for a 92 also.

What is a grid ohm? I used an ohm meter to check my lines. My defrost was cutting off also, I couldn't figure it out till I removed the rear side covers that pop on and off by the rear window, I then found the wire leading to the window had worn the insulation off and was contacting the metal lip. The cover looked to be putting pressure on the wire against the metal lip. Don't know if this is your problem but it wouldn't hurt to check. I repaired the wire and problem solved. This is for a 92 also.

I was refering to the wires printed on the inside of the glass surface, sometimes referred to as a "wire grid".
I was hoping someone would have the correct Ohm value (resistance) between one side and the other. I have checked the wire connections you describe. They seem OK.