My 98 Century A/C quit working, blew a radiator hose and now has low coolant false alarms. (only 57k miles)

[n0rd5]

Last fall I bought a 1998 Buick Century with only 57,000 miles from an old relative who rarely drove. The A/C and everything else worked perfectly last fall. But this spring I used the A/C and it wasn't blowing cold. I drove 10 miles home with the AC "on", and the second I get home and put it in park the radiator hose blew off soaking everything with coolant. I'm guessing the small pressure ripple caused the clamp to jump a tooth or something dumb) Nothing was broken, the top radiator hose simply popped off the engine barb. I refilled it and used the same hose, which was in perfect shape.

While trying to diagnose my A/C issues, I confirmed the fans DO turn on when I disconnect the coolant temp probe connector (ECU demands fans when it can't read the probe I've found out by testing). I jumpered the A/C clutch relay and it DOES engage the A/C compressor. The refrigerant has proper pressure (so not a leaked refrigerant issue). I cannot figure out why the ECU will not let the A/C system run. I even installed a new coolant temp sensor into the engine, no change.

The cooling fans never want to come on when the temp gauge goes over 50% (but temp never goes more than say 55% to red, (and evidently they don't come on until it is REALLY hot?), but the fans both work fine when the ECU demands them.

So I've been without A/C all summer. One time we accidentally left the A/C knob on "norm" for 20 minutes which heated up the antifreeze enough to cause a "low coolant" light to flash on the dash. I confirmed there was enough coolant, so I drained half, pulled the antifreeze level sensor, scrubbed the sensor prong itself (just a metal post) and reinstalled and refilled my coolant, burped it, went for a drive, and the low coolant light is ack on even though its full.

Another annoying quirk with this car is no trunk release, ONLY the keyfob button (never experienced that in any car, not even a glove box button). Also, when I push the door's LOCK switch, i have to hit it TWICE, it beeps once as if I have headlights on or something (I don't) and its warning me it doesn't want to lock on the first press... Is this normal behavior for this car?


I do NOT want to pay dealership prices to have this diagnosed, and am hoping someone here has more knowledge than I do, and have some input on my issues here relating to no A/C and heating up the coolant / false low level warnings. I thought I had scored a great condition car, but everything is spiraling down all of a sudden.

 

[chem_man]

Diagnosing an HVAC system can be tricky. First, it requires the use of an HVAC manifold gauge set so you can read both the high side and low side pressures. Just because it has "enough" pressure on the low side does not mean that there is enough refrigerant in the system. Secondly, you need a Digital Multi-Meter (DMM) in order to measure voltages and perform resistance/continuity checks to make sure there are no broken wires, defective sensors, etc. Third, you will need electrical schematics for troubleshooting the electrical parts of the HVAC system. Finally, you will need a vacuum pump in order to pump down the system if you find that you have a leak or need to add refrigerant.

R134a systems are charged by weight of refrigerant and not by the pressures measured by the gauge set. The only accurate way to do that is to first evacuate the system, pull a vacuum for a certain period of time in order to ensure their are no leaks, and then recharge it by weight.

If you do not have a set of HVAC gauges, you can "rent" them from most any O'Reilly, AutoZone or Advance/Carquest auto parts store using their loaner specialty tool program. A decent DMM will cost you about $30. The schematics can be obtained for free from Free Car Service Manuals from LEMON Manuals. The vacuum pump can also be obtained for "free" from the various auto part stores.

You could have a bad relay, a bad pressure sensor, etc. Also helpful will be a diagnostic chart which can also be found in the service manuals from Free Car Service Manuals from LEMON Manuals.

Good Luck!