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My recently-purchased 1979 528i appears to have a non-functioning lighter and rear defrost. The pull switch for the defrost illuminates, but nothing appears to happen. Fuses for both the lighter and defrost look fine. What to do next on either? I love this car- it's already the best car I've ever bought!

Check for voltage back there with the switch on, but my guess is the grid is gone. Since it's surface mounted, it can only take so much cleaning and condensation before the resistance goes sky high. New I think they're 1-2 ohms. Up to 5 ohms they'll still work ok, but they can go up to near infinity, megohms in which case they won't work. E28 rear windows will interchange but even they are old now and getting rare, just not as rare. And I have bought and changed the rear glass before to get the defrost to work.

OEM rear glass shows still available, $435 on RealOEM

If you have a multimeter, it should be easy to check the voltage on the rear window, there is a spade connector on each side of the window.
You can also measure the voltage in the lighter. I believe I had an issue once with the ground cable falling off of it.

Thanks for the tips! Using a meter, sure enough, voltage gets to the grid but not through the grid. A rear windshield looks like the fix... There isn't voltage getting to the lighter. What's the easiest way to get to it to check wiring, do I pop out the ashtray underneath it?

Peter,

Don't have it in front of me for pics but when I removed my non-working lighter the assembly was cracked and falling apart. I found a used assembly and it works fine.

If removing the center console, be careful to find and remove the screws into the trans tunnel, they're behind the ashtray and the toughest to access.

I didn't know operating cigarette lighters were still legal.

T.Hanson wrote:I didn't know operating cigarette lighters were still legal.

The lighters aren't but the outputs are used for cell phone charging.

Of course you can light a cigarette with the car lighter (in US) but who does that? The receptacle is to keep your cell phone charged so you can text, Duh!