In this particular case the vehicle is a 98 S90 but I know the ECC came on the 960's and probably some 940's as well so I'll post this question here.

2 issues :

- To get 72F inside the car with the floor (heat) setting on the ECC I have to raise the temp control knob up to 78. This has slowing been getting worse over time. As in, I used to have to set it to 74, then 76, now 78.

- With a cold engine and cold cabin, with the ECC controls in Auto (Fan Speed), Auto (Position Setting), 72F (Temp Knob), the HVAC fan comes on low immediately when the engine is started. According to the HVAC Green books, the HVAC fan is not supposed to come on until the engine temp is at least 95F and the cabin temp is 64 or less so that cold air is not blowing on you until there is heat in engine.

After reading the Green Books :

- I cleaned out (and checked the resistance of) the Cabin Temp Sensor in the Cabin Dome Light. Then I wound up changing it out. That didn't help

- I then checked, then finally replaced the HVAC plenum temp sensor in the passenger's side of the unit. That didn't help.

- I also then checked, then replaced the Heater Core temp sensor on the driver's side of the unit. That didn't help.

Has anyone experienced either of these 2 issues and solved it?

I'm about at my wits end on trying to figure this out.

Thanks, DEWFPO
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1998 S90 088,900 and 1995 964 154,100

Take of the solenid distribtion block two scews its located under the glove box you will see the colored vacuum lines goint to it.You will have to work the lines off. On the back of it there is a circuit board look over the solder joints and look for dry joints cracks if so re heat the solder. This peice can cause all sorts of problems.

Thanks for your reply.

I've checked the heater control valve and it works the way it should and only when it should. It also holds vacuum well and doesn't leak.

I can replace the solenoid valve bank (I have a spare that I replaced in a 1995 960 years ago) but I don't see how that could be the issue since it only opens and closes the doors for the positioning of the vents, and allows the heater control valve to open/close. It doesn't blend or mix air. I've checked the air coming out of the the different positions and the solenoid valve bank and vacuum bellows seem to be working and holding vacuum.

This really has me stumped and I've checked or replaced the parts that should be affecting this (as per the green book).

I've heard some of the B6304 engines have two engine coolant temp sensors (one for the dash gauge and one for the ECM) but I think this 98 S90 only has one. The dash gauge reads fine, the engine runs perfectly. But I'll throw a scanner on the OBDII ports and check to see what the ECM is actually seeing.

On this model the ECM supposed controls some of the functions of the ECC system.

Thanks for your thoughts.

DEWFPO
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1998 S90 088,900 and 1995 964 154,100