Gas and Oil Home Heating Furnaces - Help on Miller furnace/ air conditioner

When we moved in here in oct we had alot of problems with our furance. We had someone come out and put a new thermostat. When he did for some reason when we turn on the a/c it doesnt automatically kick on like the heat does. So we have to manually turn the fan on "ON" Instead of auto on the furance. Today it was close to 90 outside and the coolest it got in here was 82, it was set for 70. We also dont have a filter on the furance, but im not sure where exactly to put it. I dont have a manual for the furance or a/c. the furance is Miller. The A/C is "High Efficiency (10 SEER) - 208V/230V/60Hz". Any help would be appreicated.

Just so I know if we are talking about a package or split system A/C, is the outdoor unit about two feet square or about five feet long, 2-2½ feet deep & 1½ feet high?

I think its a split..

Model numbers on both the furnace & outdoor units might help me help you.

Since this post originated in mobile homes I assume it is one. I think MH units are slightly different than conventional home. I have a rental trailer with a heat pump and it has no real air return with filter. I had to rig up a way to hold a filter in the louvered furnace door. Although it isn't a great fit it beats no filter at all. I can't help you with the operational problems but I'm sure these heat & air boys can with enough info. :)

Sorry guys im not too great at this, lets see what i can help you with..On the A/C all it says is nordyne and Miller..On the furance it says model number MGHA-075ABFC-01 serial number MGHP105-03748..If you could give me some direction as to where the serial and model number would be on the a/c i could venture out there and look. Thank you once again!!

The info on the outside unit is usually located at or near where the electrical hook up is.

Okay, i see where its suspost to be, but theres nothing there. It doesnt even look like it was ever printed on there. Im sorry im like no help over here.

If you contact a local Miller or Intertherm dealer they can get an air filter kit for you. With no filter in the furnace, the indoor coil of the A/C is likely quite dirty. This could have a major influence on the cooling ability. You can get to the coil by opening the compartment below the furnace. I have found a toilet brush to work well in cleaning the coil.
As to why the fan won't come on automaticly, I suspect a bad thermostat or improper wiring. When you manually turn the fan on, is that at the thermostat or at the furnace itself?