Galant rear screen and wing mirror demisters issue

[Big Al]

My Galant VR4 2001 rear screen and wing mirror demisters are very slow to heat up (work). They have voltage to them, and they test as having continuity. They just take ages to work if at all. Try 20-30 minutes???. I've had the car for about a year, and has been like that since I've had it. Does anyone have any idea how I can improve them?

 

[GLen20]

Sounds to me like you have a high resistance in the element or, if it is common to both rear windscreen and wing mirrors - dry joint somewhere in the cabling/switch/circuit that is causing the voltage to fall away when you turn them on and current is demanded.
What voltage is appearing at the element terminals when they are all connected up and switched on

 

[naughtika]

check the fuse visually then go from there..

 

[Big Al]

Thanks guys. Fuses are fine. Tested that. I have 12v at the screen, and the earth on the other side is good. demister wires tested continuous. I wondered if there was a history of the demister resistance wire degrading or changing resistance on these model cars. If not, and assuming the demisters worked fine from new, I guess I will start looking for a bad connection.I was hoping it wouldn't be a bad connection inside the fuse box itself. I'll have another look in the weekend. Cheers.

 

[GLen20]

The demister element must have some resistance. With the wires disconnected, I'd measure what the ohms are at the element terminals.
Then reconnect the wires, pull the fuse and measure the ohms at the fuse terminals (to earth) with the switch on. (you get what I mean).
Will be able to test entire circuit then and see if it is complete