There are 2 voltage supply relays in the "hydraulic" unit, under the black plastic cover. The silver one is a common failed part 001-542-65-19, list is $37.
Glow system problem related to GLOW PLUG failure!
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)