If I wait until the dash indicator gets red hot it seems to take quite a while and it is very hard to see in bright daylight so I was trying to improve my waiting time (this from a person driving a 240d auto) and give the system a break.
This car has unknown miles and seems to start a little slower than I like so I am guessing the compression is lower than it should be so keeping a good battery, good starter, and good glow plugs will help alot.
I am guessing the first gp in the series is the one next to the firewall so I can just check voltage starting with that one and I should have some voltage to the grounding strap.

I seem to remember a post from a year or two ago that mentioned switching this type of glow plug system to a newer type, anybody familiar with this?

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Ncnetman
1978 300cd fresh paint
1965 Mustang
1968 Torino GT fastback
2015 VW Passat TDI
1969 Ranchero- project
1974 240d 4-speed -for sale
1976 240d - for sale
1990 6.2 Suburban 194k-getting a 6.5 turbo
2008 Duramax Silverado-totaled
1959 Chev 3100 Fleetside - sold