So, for starters, I'm going to assume everything on your truck is stock and unmolested.
There were at least two types of glow systems (fixed glow and superglow) used, depending on market. I can't say for certain which your truck has, but if it's a superglow system, there are two relays and a glow timer. Here's a schematic of the superglow system:
The primary glow relay looks something like this:
And the secondary (afterglow) relay looks like this:
Last but not least, the Toyota glow timer unit will look similar to this:
Now, if your truck only has one glow relay, that tells me you probably have a fixed glow system that only uses one relay... but it still has a glow timer unit under the dash. Here's the schematic of that:
Both glow systems operate in basically the same way - the glow timer determines the amount of time to "glow" the plugs. On the fixed system, the glow timer operates as a fixed timer. In the superglow system, the glow timer takes an input from a water temp sensor that tells the timer how long to glow the plugs. It also uses a second relay to continue to "after glow" the plugs (through a resistor to reduce the current) for a period of time after the engine has been started to ease the cold start warm up.
Hope this helps!
