1985 300 Sd...
 

My glow plug light on dash is not always lighting up when I try to start. When this happens, it takes me longer to start her up.

When it does light up prior to starting there are no problems.

IS this the cars way of telling me the relay is bad? If so, where is it located?

Thanks for the help.

I believe the relay is mounted on the front left fender. There is an 80 amp fuse there also that is screwed into the relay. Be sure to check it carefully before replacing the expensive relay. Those fuses develop an intermittant problem with cracks and poor contections. Might be just as easy to pick one up and replace it now. Most of us carry an extra glow plug fuse in the trunk.