My glowplug light stays on. I just bought the car a couple weeks ago and was informed by the owner that it needed a new glow plug relay, which I bought (used) and replaced today. The first time I started it it turned off after a few seconds just like it was supposed to. But on the way to school today I look down and the glow plug lights stuck on. So I'm back to opening the hood, plugging the relay in, starting the car, and unplugging the relay any time the engines cool. Could it just be the temp sensor keeping the light on? and is there anyway to tell without a multimeter? Can't really hear anything..

 

The Glow Plug light will also stay if enough of the Glow plugs are not working.

If you live in the US Harbor Freight Stores sell Multimeters for $5 or less when they are on sale.