77 NYB rear defroster doesn't stay on

[Great_White]

Hey y'all,

I had to use my rear defroster this morning for the first time. I moved the switch up and the light turned on, but as soon as I released the switch it returned to the center and the light turned off. Is there a relay that should hold it on, or a physical latch that will hold the switch in the up position? It was early in the morning and I wasn't fully caffeinated, so if I'm an idiot and missed something obvious that's my alibi.

 

[FURYGT]

Formals are outside of knowledge base. However, I would think that either the switch is bad or a relay or the timer that keeps the rear window defogger grid on for a specified period of time is bad. Suggest you obtain or download a Chrysler Factory Parts Manual and a Chrysler Factory Service Manual for your car and see how the system is wired and what parts are involved to determine what you should be testing. I would check the wiring to make sure that there are no loose wires or unplugged connectors.

 

[thethee]

Is this the electrically heated rear window?

 

[Great_White]

Is this the electrically heated rear window?

Yep, it's got the wire grid on the glass.

 

[thethee]

For the electric defrost the switch is supposed to return to the centre position. If the light turns on, although briefly, leads me to suspect the heated window works but the timer inside the relay has failed.

Not familiar with a 77 NYB but on my 75 the relay is mounted inside the lower dash panel. If you remove the glove box you can access it.

 

[Great_White]

For the electric defrost the switch is supposed to return to the centre position. If the light turns on, although briefly, leads me to suspect the heated window works but the timer inside the relay has failed.

Not familiar with a 77 NYB but on my 75 the relay is mounted inside the lower dash panel. If you remove the glove box you can access it.

Excellent info, many thanks!