97 w210 no glow plug light
 

I have a 97 w210 e300d. the battery has been tested to be good and is charged. car turns over but no glow plug light on the dash. I have opened the glow plug relay and it looks like all the fuses are intact. I do not hear a click of the relay and it doesn't get warm to the touch. I have been searching forums but haven't found any one that has resolved this issue.

Check your wiring connections at the relay. There is a 2 pin connector, with small wires, under the relay. One wire is a serial data link to the ECU that tells the glow plug relay to turn on and also passes health data on the glow plugs back to the ECU. The other wire is the starter signal input to the relay.

I think a forum member on here a while back had trouble with that 2 wire harness making good contact with the relay and that may be why you don’t hear it engaging.

No glow plug = no go on these engines.

Are you getting any OBDII codes?

for some reason I never saw your reply to my post. I have checked the two wires with a volt meter and there is 7 volts when I turn the key to the glow plug position.

That won’t tell you anything. One wire is purple and will be circuit 50 the start command.
The other wire is a bidirectional serial data link to the ECU. The relay is commanded on and off by data exchanges with the ECU over this wire.

Search for a thread from tjts1 he had this problem with that connector falling out which renders the relay inoperative.

found his post. before I could troubleshoot anything else I came home and my dad had started to take the glow plugs out. we took them out and reamed out the holes. we touched the glow plugs to the battery terminal and ground and they started smoking so we know they are good. we put the car back together and went to start it. glow plug light came on but the damn battery was dead. went to charge the battery and after the light wouldn't come on. I saw something somewhere about disconnecting the battery and clearing the fault on the computer and trying again. crazy as that sounds it worked. I disconnected the battery for 30 min or so and tried again and the glow plug light came on and we got the car started.

Reviving old thread that was helpful. I've been deep leaning my 1997 E300 in prep for sale. So, I've been around a lot of wiring, cleaning behind the trunk liners, cleaning under back seat back & bottom, cleaning under driver's dash, cleaning behind or under the climate, radio, ash tray, and center console. Leaving the doors open so much the last few days, the battery ran down as expected. Charged it last night with my 10A charger, but car would not start today because glow plugs would not engage. No glow plug light when trying to start. Also, infrared (un)locking doors did not work, but I got my other key and that worked. Final weird thing was that my OBD II reader kept saying No Link with the ignition on. I found this thread, disconnected the battery, and now the glow plugs work and the car starts & idles fine. (Still on ramps, stands as I have things to do below.) But, I get a "Check Engine Electronics" and my OBD II reader, which works after battery disconnect, gives me a P0600. I was getting this dash message previously this spring/summer, but I had not read the code until today. I looked up P0600 and there's a lot of mentions about the K40 relay. I'll research that and reply to the appropriate thread(s) on that issue. I just wanted to share my experience on how this thread helped me out.