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May 29, 2005 1:57 PM

I have a POS, 1990 Mitsubishi Galant. The air conditioner doesn't work.

It's a hand me down from my grandmother, so it's only got about 83,000 miles on it. During the winter months, the car would not heat up - often the temperature gague would stay down near the coldest indication. Turning the heat up full blast would produce only cold air blowing from the vents. Now that summer is almost here, the air conditioner doesn't work either. Setting it at the coldest temperature produces a steady flow of hot air. The temperature indicator on the display panel shows it going to the middle range, so the engine is not overheating. I got the car in June of last year, and last summer the air conditioner worked just fine. Any suggestions?

posted by LilBucner to travel & transportation (9 comments total)

leave the windows unrolled?
posted by delmoi at 2:14 PM on May 29, 2005

Sounds like the AC is not helping (duh), but if you pay someone to refill the Halon (or whatever), it usually turns out the rubber gaskets, etc., are jacked. Sometimes worse and more expensive problems. The gaskets will crap out if someone doesn't use the AC once in a while to keep them moist.
I hate to say it, but you probably need someone who knows to look at it.
Being that the heat doesn't work well either, maybe the dampers are frozen? I'm in over my head here, but someone else should know for sure.
posted by unrepentanthippie at 2:28 PM on May 29, 2005

Disclaimer: I am not specifically familiar with Mitsubishis or Gallants. There may be a Chiltons or a Haines manual for 90's Gallants that would explain all this better and with pictures.

The heat is more important than the AC, fix the heat first.
When you turn on the heat you do get moving air. This means the switches and fuses and blower motor work and the ducts inside the dash are OK.

Can you find the radiator for the heater and touch or look at it? Usually they are buried in the dash on the passenger side. It would have lots of metal fins running along its side and be housed in a plastic container roughly the size of a big shoe box that connects to all the air ducts in the dash. It is sometimes just over the front passengers feet.

If it heats up, but the air comes out cold, then something is interfering with the heat exchange. I would look for leaves or something plastered against one side of it, (the side that is hard to see of course) preventing air from flowing through.

If it does not heat up you should look up in the engine compartment. There should be two hoses that lead from the engine to the heater. Hot water is supposed to come from the engine through one hose, have heat removed by the little radiator in the dash, and have the now cooler water come back out to the engine through the other hose.

Is one of the hoses kinked or blocked or missing or collapsed? Is it possible that the radiator fluid is very low in your engine and it's not really making it up to the heater?

If you feel ambitious you can disconnect the lines that lead from the motor to the radiator (when you disconnect them radiator fluid will want to spill out, so be ready to plug them.) and take a garden hose and see if water sent in through one pipe comes out the other. It should go through fairly easily. If water won't go through or only goes through in a miserly little trickle then the radiator is plugged and probably should be replaced.
posted by Ken McE at 2:33 PM on May 29, 2005

The fact that you couldn't get any heat in winter suggests that you are simply low on coolant. Ken McE has alluded to this, but it bears stressing.

Check to make sure there is coolant in the overflow bottle. If there isn't, add it. I feel fairly positive that this will fix it. If not, your thermostat may be going. But I'm betting low coolant.
posted by Mayor Curley at 3:38 PM on May 29, 2005

If the engine doesn't heat up at all I would strongly suspect your thermostat is stuck open. If there was a problem with the radiator itself the car would overheat - not the reverse. If the heater matrix has gone it usually manifests itself with water dripping into the footwell - unless this is happening I'd check the thermostat first - on some cars matrixs can be bloody hard to get at. A bit of googling vrings up these instructions which may help. As for the A/C I have no idea - in these frosted climes we have no need for them...
posted by prentiz at 5:14 PM on May 29, 2005

I agree with prentiz. If your temp gauge stayed low, even in winter, the thermostat isn't closing. It's supposed to restrict coolant flow when the engine is cold, to maintain proper operating temperature. If it sticks closed, the engine overheats. If it sticks open, the engine stays too cold, and you get no heat. (That wastes fuel, too.)

The AC is probably a separate problem, because it's a separate system (except for the air moving parts).
posted by Kirth Gerson at 6:06 PM on May 29, 2005

Removing the thermostat used to be a "quick-fix" for overheating problems but has the down-side of not allowing the engine to heat up in cold weather. There is little doubt in my mind that this is why you have no heat.

For the airconditioner, the news is not so good. You could get it re-gassed but, unless this has been done in the last few years, you will also need to get a new receiver-dryer at least, because of the change to the new CFC-free gas. You may also find that, even after spending the money to get this done, the aircon works for two weeks and then fades away, because you need to turn the aircon on regularly to keep the seals lubricated. The gas has molecules so small that they can work their way out through rubber hose, so it doesn't take much of a hole for all the gas to escape.

Generally, once the aircon on a car that age starts to go, you have to think seriously about whether it is worth throwing money at, because you can spend a lot of money and still not end up fixing the problem.
posted by dg at 9:52 PM on May 29, 2005

I don't know the Mitsubishi, but my car has a mono valve that determines whether the heater or air conditioner should operate. When it is defective, they both operate at once. The chances are slim, but in this case your air conditioner could be fine.
posted by weapons-grade pandemonium at 12:00 AM on May 30, 2005

Greetings fellow heapy car owner!

A/C: Worked last year, not this year, add freon. You can ramp up and do all the other stuff, new dryer and all that, or you can go to auto parts and get what you need - which is pretty much a can with a hose. Get the kind with a gage on the hose and you can see if you'll need another can. If you think it's leaking (if it needs another can two weeks later) get the dye-check stuff and add that with the freon. It'll give you an idea what it'll take to fix everything when you find the leak. (Small leak = small money, big leak = big money).

Hope it's R124 which uses and air-hose like quick disconnect. Most cars have been updated to that by now. The old R-12 Freon systems you now need a special license for the freon, and in the end it'd be cheaper to have the thing converted - that's a take-it-to-a-shop job. (I'm told the hot tip (pun!) these days is R-12a, but am not familiar with it.)

R-12 will be screw-on servicing.

Heater: If your engine gage is showing about the right temp, then the flapper valve that opens the port by the heater core (a small radiator on your firewall) allowing the heated air into the cabin isn't opening. Usually that's to do with a broken vacuum hose. The easiest way to find it is to, with the engine running, look over the hoses (the heater one will be little bitty) and spray some WD40 around (carb cleaner will work as well). The engine will run different when it sucks in some WD40. Don't be a slob, a little dab will do ya' on this test.

Your cars at about the age when this happens. In production they use little plastic hoses which get old, brittle, and break. When you find it just go to auto parts and get a rubber hose the right size and slip it on there.

Sometimes, however, it's a valve on th firewall, the valve that directs the vac signal to the flapper. If that's the case they're usually easy to get to and cheap at a junkyard.

A '90 Gallant w/ <90K miles should have a lot of life left in it. Keep the oil changed and the rest serviced and it'll go 200K miles no problem. Start letting stuff go, however, and it's a downhill ride.
posted by Elvis at 4:05 PM on May 30, 2005