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1969 Mark III Fuel Pump Update And Auto Climate Control Issues

Bill –
Thanks to Lincoln Land for the correct fuel pump. After months of fuel
issues the Mark III is running beautifully. That problem is solved !
Now a new quirk has developed. The ACC had always worked perfectly. I
now can not get heat out of the heater vents. When I turn the ACC on and
set the temp at 85 with the ambient temp outside at 50 degrees air flow
comes out the a/c vents that is not heated. I also hear the a/c compressor
engage. I do not have heat out of the floor vents. I have good heat on
defog and defrost with proper airflow out the defrost vents (a/c
compressor engages on defog/frost). I turn it back to low or high and
set the temp lever on 85 I get unheated airflow out of the a/c vents. I
hear the air blend door doing it’s little dance while the temp lever is at
85. I turn it down to 65 and the temp of the air out of the dash vents
seems to cool down ( it’s a little hard to say because it is winter ) but
I don’t hear the blend door adjusting itself as much.
Sincerely –
Patrick –
Glad to hear we could help with your fuel problem….
The compressor will be on in all positions except OFF or if the ambient temperature is below approximately 35 degrees. When the control lever is in the DEFROST position the system will drive to the full heat position (no temp regulation as the sensors are shorted to make the blend door remain at full heat setting) with maximum blower speed. In DEFOG the system will have three high automatic higher blower speeds and will regulate the air outlet temp. according to the setting of the control 65-85 degrees. The air outlet will be locked in approximately 90 percent DEFROST and 10 percent FLOOR position. Do you in fact have heat in the DEFOG position with the control at 85 degrees? In the HIGH or LOW position the system will adjust between FLOOR or the A/C VENTS as necessary to maintain the temperature that you have the lever adjusted to. The system will not drive the blend door to the full Heat position if the temperature inside the car is warm or in the vicinity of the temperature setting that you have chosen even if it is set at 85 degrees in some cases. If you hear the blend door doing its “little dance” as you describe this tells me the the blend door is not in the full heat setting. If you feel that your system is not operating as designed it will need to be diagnosed as per the Shop Manual only. We at Lincoln Land are able to repair all parts of this intricate control system including the annoying “little dance” chatter from the blend door servo. Accurate on scene diagnosis at your location of course is critical to avoid unnecessary labor and parts replacement. Before diagnosing you need to remember if the problem began after another area of the car was serviced previously and consider the possibility that some component related to the Automatic Climate Control was disconnected or unplugged etc. The main ATC box located above the carpet on the passenger side has a small inset dial on the bottom which is factory adjusted to a position near the center of its travel. If someone unfamiliar with these controls has adjusted it to the full Cold position the system will act as you are describing and will not be able to move the blend door to the full Heat position except in the De-ICE setting. I would advise you to check this dial setting before replacing parts. We hope that the above helps. Please let us know what you find.

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