Ok my plugs are only staying on for about 3 seconds when before they would be on for a good 7 or 8 seconds. Is there a temp sensor in there that tells the plugs how long they need to stay on (summer=less, winter= longer) or should it always be the same time. And if there isnt a sensor is there any way to adjust the length of the glow?

there is a temp sensor for the glow system... its on the head. drivers side.. closest to the nose of the car.. so ive been told.. id show a pic but i dont have one

The plugs don't turn "off" with the light. For about 15 seconds after the light extinguishes, the plugs continue to heat up. Some have found the car starts better starting it 15-30 sec after the light goes off because more heating has taken place.

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.

I agree, the light is just an indicator that is based on temperature, but the actual plugs stay on for about 40 seconds. If you turn on the dome light, you will see it get brighter when they click off.

I noted that a NEW glowplug connected to the battery takes about seven seconds to reach peak temperture (Bright orange / white hot)

That is why I glow for seven seconds then start, see sig



Steve

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Silver 1984 300SD, Manual glow plug timer, push the button and count!
1997 GEO tracker
1986 Olds cutlass supreme, soon to have fuel injection
Various dodge trucks hope to use the bits to make a good one......oneday.
1951 Ferguson TO30 tractor.

That's about what I've seen when I've "bench tested" them. Don't forget that it takes some additional time for the GPs to heat the air in the pre-chamber. My light goes off in about that time in the summer. If it's very cold, I usually let them glow about 15-20 seconds. I don't see much advantage to a manual system, you can accomplish the same thing by just waiting a little longer after the light goes out, and relays are cheap.