Temp gauge "ticking/pulsing" upward help?!
 

Hi all I have a problem on my new 1985 300D when I let the car run for 2-3 min yesterday temp was around 35ish (outside or ambient temp) so kinda cold, the temp gauge inside the car started to "pulse up" it was sort of like a clock work movement just "ticked" its way up to the red line and then beyond but thats impossible its that warm, So any ideas as to whats causing it? I am thinking a short or maybe the temperature sending unit. I kept on feeling the radiator and the hoses coolant is flowing and the heat is the perfect temperature. Any help would be great thanks.

Assuming your system doesn't have any leaks and there's still coolant in the head(Can you feel antifreeze in the upper hose coming out of the head?) Not enough coolant to pump would result in a cool radiator and hot head.

Electrically, pull the temp sensor plug, clean it, and put on a little dielectric grease(or vaseline). On the dash end of things, dancing needles usually means a grounding or other connection problem.

Also, the FSM will tell you how you can test the temp sender. There is a table telling what resistance is should show at different temperatures.

Thanks, I did feel the upper hose and coolant was flowing also felt the top of the radiator no cold spots, also saw the coolant level in the tank drop a little when the thermostat opened up. So all indications are that coolant is flowing through the engine.

I had the same problem I assume. I could tap the cluster and the needle would drop to where it should. Pulled the temp plug, etc. cleaned everything. Functions normally now. The sender can get pretty gunked up. Plus I had to replace the sending wire as the insulation had cracked and was shorting on the block.

Thanks guys!! :D next week will have my new toy on the road will post pics soon

Change the VDO sensor and also check the ground of the vehicle.