1972 - Thermal limiter fuse

[Jerome P.]

I continue to blow the thermal limiter fuse that is associated with the A/C compressor. Has anybody had any experiences similar to this with there A/C car? The Thermal limiter fuse is on, I believe, must c-3's to at least 1973. The system has a full charge of refrigerant.

[Edward J.]

Re: 1972 - Thermal limiter fuse

Jerome, you'll need the just by- pass the limiter and test the a/c pressures with gages, if the low side pressure is dropping below the normal spec. This will cause the limiter to to heat up and blow,

Note: the normal pressure all depends on the out side temp. generally about 26-32 PSI is the norm, The hotter it gets the higher the colder the lower the psi.If you have a shop manuel its spelled out in there.

A bad POA valve could be the cause. if the pressures are higher or lower tahn normal.

[Jack H.]

Re: 1972 - Thermal limiter fuse

1972 was the debut of an 'improved' A6 compressor that featured an integral superheat switch. The system was intended to automatically turn OFF the compressor (drop power to the electric clutch) in the event the compressor lost pressure, dumped refigerant along with its oil, and the A6 compressor began to heat toward a melt down.

I've encountered some cars from this era where 'Bubba', not understanding the function of the superheat switch and the wiring differences that supported it, made cleaver underhood modifications to force system functionality...

I'd start by reading the theory of operation section pertaining to the A/C system in your copy of the 1972 Chassis Service Manual and seeing if they offer special words of advice regarding troubleshooting the system from a superheat switch viewpoint.