it looks like a starter relay and its on the passager side valve cover area (powerstroke57) He is correct but be sure that you don't mistake the intake heater relay for the GP relay they are the same relay and are right next to each other. The Glow plug relay will have a orange and black wire to it that goes to the starter relay.
wire diagram for 1999 Ford F250 diesel glow plug relay
the glow plugs are located under the valvecovers should be 8 of them
on top of engine on passenger side behind warm air relay they look the same but the glow plug relay is the shorter one
On the engine compartment side immediately next to the battery
Mounted to the passenger side frt valve cover
glow plugs, glow plug relay, poor compression on engine are some things that will give problems
how locate glow plug relay on 2008 Volvo diesel 2.0D
no glow plugs
it controls the time the glow plugs are on up to 120 seconds depending on temp and other information recived from the pcm
The 1991 Dodge diesel truck glow plug relay is located in the fuse box. The fuse box is located behind the battery box. The glow plug relay will be in the right upper corner of the box.
Unless your ford focus is a diesel your car does not have glow plugs.
Inside cab, to the left of the steering column under the dash is the relay / fuse panel. On that panel is the glow plug relay.