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1970 Mark III AC Concerns

Hi so I was led to your website through the question made by Chris, where his blower motor would not turn on. His relay was getting power and only one set of wires was getting power on the resistor. Well I’m having the exact same issue and it only works if I jump 12v from the relay to the resistor but I don’t think it’s working right. I couldn’t remember the whole thing so I had to make a list as I tested the settings so that I could get the whole thing down. I’m pretty sure it has tons to do with vacuum leaks and being ancient but here it is

On high at 85 it doesn’t seem to blow that hard also no air comes out of any vents, when placed at 65 the speed picks up and the vent hole thing on the passenger kick panel opens up, still no air appearing to blow anywhere.

Low will blow on 85 only if I blow warm air on the temperature device in the dash. If I place it at 60 it’ll blow. Still won’t push air through any vents.

If you place it on defog you can kinda feel air come through the defrost vents but it isn’t even enough to defrost the windshield. Also defog doesn’t blow warm on 65 or 85

De ice blows warm on on 65 and 85 and still doesn’t blow hard enough to do the job.

Lots of air comes out of the hole where the resistor is supposed to be inside and right around the middle of the firewall kind of from the air vents that suck air in which I find odd. Thanks.

Gavin –

Hi Gavin –

The Automatic Climate  Control on your Mark III is an excellent system. It is complicated though and requires the correct shop manual to diagnose and repair. From your description, your issues sound like you may have more than one problem however. If you do not have the correct  shop manuals we do have them available for you here at Lincoln Land.

Most of the problems on these systems have proven to be located inside the ATC box and or the servo unit. We can test and repair these units here at Lincoln Land if the are suspected or diagnosed as faulty. Another issue arises if a previous technician has unknowingly modified some parts of the wiring or vacuum circuits and has actually caused further problems. To accurately diagnose your issues without guessing, your Mark should be diagnosed by someone on sight with the use of the correct shop manuals.

Let us know if we can be of further help.



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