98 Grand Caravan A/C control head

[ggrieves]

Recently purchased this 98 Grand Caravan. The A/C would only cool part of the time, usually just a little right after the engine was started. The seller said he had a mech check it out, (did not run any actual diagnostics) The A/C button would not stay pushed in or light up on the controls so he suggested that the control head might need replaced. I had a buyers check done and the mechanic who checked it out said the same thing; possible bad control head. I purchased a used control head and it lights up, actually four of the selections flash on and off. I found a repair guide in the van that said when replacing the A/C control it would need calibrated. My question is, can anyone tell me how to calibrate/reset the control head? I had a can of freon put in the unit in case the a/c was only cooling part of the time because it was low on freon and that mech said the compressor was staying on all the time. There was a language barrier, he did not speak much english, but I think he said that it could use more freon. I will need to check that out again but right now I need to get the control working. Any help would be greatly appreciated.