1995 E320 Climate Control

[300CE]

Earlier this year I purchased a very nice well care for low 80k mileage - 1995 C124 from southern California. During my PPI I noticed there were some erratic heating issues and I’m now at a point where I can tackle the last item on my to do list, the unreliable heat issues.

The A/C works very well as it gets very cold. When turned to max cold the blower fan cycles to very fast and then the blower speed steps down when the temp wheel is adjusted. This is the same in AC and EC modes. It seems not to be calling for / or missing hot water.

My test of the heat, sometimes when the temp wheel is near max heat I don’t get any heat. If I turn the control unit off and then on in the defrost mode I’ll get plenty of hot air from the defrost and out of the side vents. When I place the temp in the middle, 72 degrees, I get warm air out the side vents for a while and cooler out the center.

This is what I’ve tested thus far:

I’ve checked for trouble flash codes, none indicated.

Aux heat pump, it turns off and on with ignition switch, it measures 3 amps and even hot temps on hose connections from the right hand feel test.

Mono valve; I get heat when I unplug it, measures 13.2 ohms ( in range 11-19) Replaced Heater Mono valve and aux heat pump.

Interior Temp Sensor; revealed expected changes in ohms from 3 to 24 when changing temps from 100 to 32 degrees in range.

Sampler Blower, no suction at inlet will not hold tissue. Replaced sampler pump, No leaks on suction tube to blower, pump runs very little suction at inlet to blower but will hold tissue. No dust / dirt blockage!

I need help and guidance of what to do next.