1993 W124 300D After-glow

[i-osprey]

My problem is this:

I have installed new glow plugs and injectors but I am still having problems on cold starts.

The engine starts just fine and runs fine for about 10-15 seconds.

Then it gets rough and plumes of white smoke come out the exhaust.

This morning it was about 50F when I fired it up.

According to the charts I have seen I should have about 30-40 seconds of afterglow at this temp.

I don't think I'm getting that.

From what I can gather from all the posts I've read on the subject, it could be my GP relay or my temperature sensor.

I am getting glow at first and it starts fine so I doubt it's my relay.

Could all of this be caused by a bad temp sensor to the GP relay?

If so, what exactly is this temp sensor called?

I have searched in parts but I haven't found what I am looking for.

The sensor is located between the water pump housing and the thermostat housing.

The wire runs from there to the GP relay.

I have noticed that one of the clips holding the wire onto the sensor is missing but it is still firmly attached to the sensor.

Is this the only temp sensor on the engine?

Is there a way to test it?
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I don't want to confuse the situation too much at this point but I am also having an ongoing problem with my HVAC.

When the A/C is on and I floor it to pass somebody the A/C will stop cooling and immediately start HEATING the cabin.

I have to turn it all off, wait a few seconds and then turn it back on in order for it to start cooling again.

Could this be the same temp sensor or is it another problem entirely?