Hi I have a 87-88 300D W124 with the 603 donk the tac is intermitaant and it takes the AC out.

I have tested the tac sender as another contributer kindly told me to. its ok

Read your thread and thought great way to test the instrument.
if the sender and instrument are sweet it should be the relay or another sender to it.

My relay ERL PN 004 545 3632. has blanked pin 5 and now wires of the same coluor but my D-Klima PN 001545 80 50 does.

Any one know what i've got wrong or is it just because we drive different rides?

Any one know the if then equation and pin outs for my ride?

thanks for your time and contibutions

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Peace and Blessings to you and yours
Steve

1987 /88 300D 178K & Very tidy
WVO RUG Diesel Blend OEM fuel heater thermostat by passed
1991 Nissan Patrol TD42 350k & very rough
WVO RUG Blend return line to cav 296 filter