96 lumina issues

I have some few issues with my 96 lumina (3.1 base model). It has had a full list of repairs but it has 172,000 miles and still is in good condition (for the most part)

My A/C went out this summer, how would I go about figuring out if it just needs a recharge or if the a/c compressor has a short or is seized?

My other issue is I was wondering if it was possible to mount a external tach and hooking it up, it doesn't come with one stock btu was wondering if there was a way to easily hook it up.

The other thing thats been confusing me is at abotu 169,000 miles my tranny went *poof* i had nothing but 1st gear. (kinda) so I had the tranny rebuilt and parts replaced. MY confusion is here. My 2 other cars with automatic trannys shift very smooth always everytime, my lumna on the other hand shifts sluggishly (usually when its warm, when its cold it shifts quite smoothly). Went it shifts it jerks forward but not too bad to where its grinding or missing.

And now my latest problem is little to no heat. I have checked the antifreee fulid and it is up to the proper level. However sometimes driving I will see my temp gadge climb and climb (one of the fans kick on, should both of them kick on?) Then out of the blue from about 205 degrees it goes all the way to 120 ina flash. Something isn't right, I have little to no heat comign from the blower and when the temp reads 205 the engine is cold to the touch. Is it a bad thermostat?

Car is getting old, I just need it too last me another 28,000 miles.

Concerning the tach issue, you can grab a used cluster off ebay and simply drop it in; connectors are the same. If you want an external tach, there's a white wire coming off the ICM that is the tach reference signal.

As far as the heat, the motor on the door that controls where the airflow comes from (heater core or AC) is probably shot, or the switch is fried.

The AC problem could be low charge, bad AC clutch, or might be a bad wire/switch.

I find the dash thermostat is wildly inaccurate. When its halfway, it should be 160° but the ECT reports about 205° halfway. I've worked on a couple of Luminas where this was the case, though it could be that all the ECT/PCM/dash clusters were screwed up. Fan 1 should kick on at 210°, 2 should kick on at 225° (approximate), however 2 should always be on if the AC is on.

As far as the heat goes sounds like there alsomight be air in the coolant system that can be bled out using the bleeder valves at the front of the motor(one on the thermostat housing and one on the far left side of the front of the motor)