72 Cutlass Supreme, factory AC car.

AC has been working great for the last two years. Yesterday I tried to turn it on and didn't have any response.

Compressor didn't start and no blower motor on any speeds.

Replaced the Heater A/C 20a fuse with no luck.

Where should I look next?

 

Was the old fuse blown? Have you verified power on both sides of that fuse?

 

I might be incorrect, but I believe there is a step-by-step troubleshooting dichotomous diagram in the AC section of the CSM.

 

Went back out to double check and it turns out neither of the spare 20A fuses I tried had continuity.

Installed a good 25A and all is well.

Appreciate your assistance.

 

The OEM fuse is a 20A. Did the replacement 20A blow as soon as you installed it? If so, using a 25A is a good way to start a fire.

 

As Joe already correctly pointed out the OEM fuse is 20A. That fuse needs to remain a 20A fuse to protect that circuit. Wires along that circuit are rated to carry a certain amperage and the fuse size is designed/sized to protect that circuit. If you allow more amperage to traverse that circuit (e.g. 25A) than the wires can accommodate, heat builds up in wires, crimps, solder, insulation, etc. and it could become a far more serious issue. Melted wiring/insulation, etc. can invoke bad things. I know you had some electrical issues (asking for assistance) on other threads in the forum. Please ensure you're following good electrical practices & don't short-cut the appropriately designed electrical wiring diagrams. The 1972 color wiring diagram is located in the 1972 Chassis Service Manual (CSM) which should be in your personal library. In case it is not, the wiring diagram can be found (below) at this URL link. Additionally, I'll post the OEM fuse panel for your 1972. Be careful with any existing wiring from a PO and be careful with upgrades you make which draw more amperage than OEM specifications. If you have questions always ask. If you're blowing the 20A fuse on this circuit, you most likely have an issue with the heater &/or AC which requires further attention.

1972 olds cutlass wiring diagram

 

Note that the wiring diagram linked by Norm is for the base equipment heater-only configuration. The A/C wiring diagram is in the A/C section of the Chassis Service Manual.

 

Exactly, thanks for pointing that out, Joe.

 

Thanks guys, got a 20A in there.