Sometimes no heat, If I squeeze the heater lines going to the core sometimes I get heat. If I unplug the Mono Valve I seem to get heat. I am not sure if it may be the CCU or the mono valve. I am not sure if this car has an aux pump. Can't seem to find it unless it is in behind the firewall somewhere. If that seizes I believe it will take out the CCU so I need to make sure of them all. I have a w124 donor car.

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1987 300 TDT
1990 300 SEL