david85
Full Access Member
They may have failed from a bad controller. The system for 1986 and older uses a thermal switch assembly that the reads into the head at the rear Driver's side corner of the engine. That will then control the glow plug relay, which is mounted on the Passenger side inner wheel well (among the mess of wires behind the battery).
The thermal switch might as well be 1930s technology because it's little more than a bimetal switch set up like a timer. They can fail in various ways, and they fail often. Mine failed in such a way that it would not switch off. Instant set of glow plugs burned out in one shot! Another way they can fail is simply not coming on at all. Or they can start cycling while driving down the road. Or they can sometimes glow for only a few seconds instead of the full 10 seconds. 1987 and up uses a solid state controller that calculates glow time based on a simple ohm's law calculation in the integrated circuit (glow plug resistance increases with temperature). Much more reliable.
Oddly enough, I replaced mine with a set of Bosch before I realized the controller was the problem all along. The tips ruptured but none of them broke off. The failure appearance was very similar to Beru when they burned out (from excess heating).
I still have the 1986 style system, but also run a three position OFF/AUTO/ON switch, with ON being momentary.
Hehe, that's how my saga started too. Although that was a separate incident with dual coil wellman glow plugs. Thinking back, it sure took a while for me to learn
The thermal switch might as well be 1930s technology because it's little more than a bimetal switch set up like a timer. They can fail in various ways, and they fail often. Mine failed in such a way that it would not switch off. Instant set of glow plugs burned out in one shot! Another way they can fail is simply not coming on at all. Or they can start cycling while driving down the road. Or they can sometimes glow for only a few seconds instead of the full 10 seconds. 1987 and up uses a solid state controller that calculates glow time based on a simple ohm's law calculation in the integrated circuit (glow plug resistance increases with temperature). Much more reliable.
Oddly enough, I replaced mine with a set of Bosch before I realized the controller was the problem all along. The tips ruptured but none of them broke off. The failure appearance was very similar to Beru when they burned out (from excess heating).
I still have the 1986 style system, but also run a three position OFF/AUTO/ON switch, with ON being momentary.
Figure if im gonna turbo it down the road ill pull the whole block and do the bottem end too
Hehe, that's how my saga started too. Although that was a separate incident with dual coil wellman glow plugs. Thinking back, it sure took a while for me to learn