On the earlier w124, say 1991, does the GP relay cycle on clod days, like the grid heaters on a Cummins?

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

GP Relay = ????

What do you mean by cycle? The way it works, as I understand it, is that it keeps the glow plugs on after the engine has started for 30-35 seconds or so. You can hear the relay click off if you don't start the engine.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 154k miles
06 E320 CDI "Rutherford", Black on Tan, 172k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 142k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Yeah, on my Cummins the heat grids cycle on and off until the intake temp reaches 60 degrees.

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

The heat grid is a different setup to glow plugs. Glow plugs heat the prechamber in the cylinder directly. Heat grids heat the air entering the intake plenum.

The glow plugs turn on when you turn the key, after a few seconds the idiot light goes out and you start the car. On earlier cars (up through 87?) that was it, the plugs shut off when the starter engages. On later cars the plugs will continue to run in "afterglow" for up to 90 seconds depending on water jacket temperature, then shut off. If the water jacket is warm enough, the afterglow doesn't take place at all.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

W124 GP relay measures water jacket temperature and adjusts the length of time of glow based on that. Below a certain WJ temperature it may call for an after glow to reduce smoke and help with ignition. I thought the after glow was 90 seconds at a slightly reduced voltage.

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92 e300d2.5t
01 e320
05 cdi
85 chev c10

Ok, I get it now. I knew glow plugs were different than grids. It was below freezing today after work, and noticed the windshield wiper was moving slower.

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K