why are the GPs on separate wires?
why are the GPs on separate wires?
why aren't the GPs just wired in parallel on one big rail? would something bad happen if i replaced those 5 wires with one big one?
english red rat rod 1977 240D, OM617.952 burning B99.9, iron 4-speed & 2.88 diff, 195/60/R14 on alloys, 5mph bumpers, battery in the trunk, 25mm swaybar, 4x ECE H4 lamps, double brake lamps, deleted sunroof, export zoll & california blue plates
i have an '85 GP relay with 5 outputs and 5 wires leading to the 5 glow plugs.
why aren't the GPs just wired in parallel on one big rail? would something bad happen if i replaced those 5 wires with one big one?
english red rat rod 1977 240D, OM617.952 burning B99.9, iron 4-speed & 2.88 diff, 195/60/R14 on alloys, 5mph bumpers, battery in the trunk, 25mm swaybar, 4x ECE H4 lamps, double brake lamps, deleted sunroof, export zoll & california blue plates
DiseaselWeasel
03-17-2017, 04:02 PM #2Depending on which plug fails, all following fail too... With separate wires you have only one failing and starting is still fairly easy. Up until ~'80 (IIRC), plugs were actually wired in series...
The connector wires would get very hot, and IIRC when one glowplug failed none would work.
With the 5 individual connections, you still get adedquate glow (most of the time), even with one glowplug burnt out.
Old syle loop glowplugs were wired in series, but there is too much of a voltage drop when wired in series.
The connector wires would get very hot, and IIRC when one glowplug failed none would work.
With the 5 individual connections, you still get adedquate glow (most of the time), even with one glowplug burnt out.
Series plugs have nothing to do with an '85 car and should've stopped production 30 years ago....
1978 300D, 373,000km... OM617.912 with a Holset HX30W, 7.5mm IP, 711.113 5 speed (project car, 7 years off the road and counting ;/)
1977 250 270,000km (parts car)
1977 300D (ex 280) 500,000km
1981 240D 498,000
1975 HJ45 ???,000
2001 2.8TD Rodeo 4x2 - 456,000 - DD
There is no reason not to wire the plugs off one connection, MB made individual wires to detect if a GP had burnt out with a clever GP relay.
Series plugs have nothing to do with an '85 car and should've stopped production 30 years ago....
1978 300D, 373,000km... OM617.912 with a Holset HX30W, 7.5mm IP, 711.113 5 speed (project car, 7 years off the road and counting ;/)
1977 250 270,000km (parts car)
1977 300D (ex 280) 500,000km
1981 240D 498,000
1975 HJ45 ???,000
2001 2.8TD Rodeo 4x2 - 456,000 - DD
what are the more common failure modes of GPs in fact?
english red rat rod 1977 240D, OM617.952 burning B99.9, iron 4-speed & 2.88 diff, 195/60/R14 on alloys, 5mph bumpers, battery in the trunk, 25mm swaybar, 4x ECE H4 lamps, double brake lamps, deleted sunroof, export zoll & california blue plates
series is just a bad idea all around. in parallel, like NZScott said, one advantage is in independent treatment of the power lines. i'm not sure if plugs ever ever fail closed but a breaker for each would let one line go out and leave the rest working. if failing open is the only problem then the one failed plug will fall out on its own accord, unlike the series circuit.
what are the more common failure modes of GPs in fact?
english red rat rod 1977 240D, OM617.952 burning B99.9, iron 4-speed & 2.88 diff, 195/60/R14 on alloys, 5mph bumpers, battery in the trunk, 25mm swaybar, 4x ECE H4 lamps, double brake lamps, deleted sunroof, export zoll & california blue plates
what are the more common failure modes of GPs in fact?
english red rat rod 1977 240D, OM617.952 burning B99.9, iron 4-speed & 2.88 diff, 195/60/R14 on alloys, 5mph bumpers, battery in the trunk, 25mm swaybar, 4x ECE H4 lamps, double brake lamps, deleted sunroof, export zoll & california blue plates
series is just a bad idea all around. in parallel, like NZScott said, one advantage is in independent treatment of the power lines. i'm not sure if plugs ever ever fail closed but a breaker for each would let one line go out and leave the rest working. if failing open is the only problem then the one failed plug will fall out on its own accord, unlike the series circuit.
what are the more common failure modes of GPs in fact?
english red rat rod 1977 240D, OM617.952 burning B99.9, iron 4-speed & 2.88 diff, 195/60/R14 on alloys, 5mph bumpers, battery in the trunk, 25mm swaybar, 4x ECE H4 lamps, double brake lamps, deleted sunroof, export zoll & california blue plates
You will need to figure out some way to balance the current to the individual GPs. That will be a challenge if you wire to one, then from there to the next one. Series solves that problem, but then a single burned out GP kills the entire string. Parallel with individual wires gets close to equal distribution, even if the wires are not exactly the same length.
1978 300D, 373,000km... OM617.912 with a Holset HX30W, 7.5mm IP, 711.113 5 speed (project car, 7 years off the road and counting ;/)
1977 250 270,000km (parts car)
1977 300D (ex 280) 500,000km
1981 240D 498,000
1975 HJ45 ???,000
2001 2.8TD Rodeo 4x2 - 456,000 - DD
Forget series!!! Dead technology. Just put the main wire to the rear cylinder and 'daisy chain' to the rest, /thread
1978 300D, 373,000km... OM617.912 with a Holset HX30W, 7.5mm IP, 711.113 5 speed (project car, 7 years off the road and counting ;/)
1977 250 270,000km (parts car)
1977 300D (ex 280) 500,000km
1981 240D 498,000
1975 HJ45 ???,000
2001 2.8TD Rodeo 4x2 - 456,000 - DD
Baldur Gislason
The reason they're separate is because the glow relay monitors the current to each plug for diagnostics. A handy side effect of that is you can unplug the glow harness and measure each glow plug at the harness connector without having to remove the inlet manifold.
Baldur Gislason
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