Hi: I have an '87 300DT with the 124 chassis. Has been running fine. The problem: the gauges for the coolant, oil pressure, and fuel all dropped to zero. The combination relay (part 201 821 00 47) is vibrating and making noise. Replaced the relay with the identical part with no improvement. Fuses are all good. I am about to test the sender units for the above guages. Any ideas?
Thanks much,
Pat