86 300 SDL, 1st MB and luvin it !
Prior to replacing light bulbs in dash the fuel guage worked as did the Temp. guage. After the fuel guage goes to full at all times and the temp. guage goes to top temp when the thermostat opens?

I have intermitant problems with the heater deciding not to work. How can I easily test for the monovalve?

Thanks for your help

John

Welcome to the forum.

Can you explain the above statement in a bit more detail. I'm not grasping the full extent of the issue.

Thanks Brian, When I start the car the fuel guage goes to full and stays there, the temp guage goes to the high temp but only when the thermostat opens (3-4 minutes of running). This started only after lightbulbs were replaced in the dash, prior to that both guages worked fine. My guess is that maybe a ground was dislodged but ? After this I also replaced all fuses, some were very old so I replaced the lot.

Problem 2 is intermitant, the heater controls will sometimes not work, whether I use any of the control buttons none will work, yet minutes later they will fully function.
Thanks for your help
John

With regard to the gauges, it's almost a certainty that one of the plugs to the cluster is dislodged and the gauges are not getting a proper ground signal.

With regard to the heater controls, it's normal for the vehicle to prevent blower operation when the coolant temperature is below about 50C. This prevents cold air from blasting the driver. However, if you must have that cold air, press the defrost button (all the way on the left). If the system is working properly, you'll get full defrost air (albeit cold) to the windshield.

Much Thanks Brian

John