A few heating/cooling/gear shift issues

[AHarris3719]

So, this usually happens in the winter more but I have a 95 Corolla DX which has difficulty warming up during the winter. (The heat meter won't ever go past the line at C. When I'm on the highway, the pointer goes back down to about a half inch below the line.

I think this is connected to my second issue. When I'm driving and get up to the 55-60 range, the car won't shift into the next gear. You can hear the high humming and although I can get it to 70+, it doesn't seem to shift UNTIL after I have been driving for awhile where the engine somewhat warms up back near the line or when I drive around first until the car is warmed up more. Then, you can feel the shift if you're going 60+ or it just naturally goes.

Last, during the summer my car is heated very well. Today was 75 degrees in Dallas and my gauge was up to 3/4 of the way to half. The issue however is when I turn on my a/c it blows semi warm air. The lower I have the air blow, the "cooler" it is. (In winter it is the same way for the heat...semi-cool especially when I'm driving on highway and warms up when I'm either at a complete stop or driving slower. slower=warmer)

What do you think the issues seem to be? Thanks. Hah

[Sine Deviance]

The problem with your engine temps not staying high enough can be credited to the thermostat. Modern thermostats are designed to stick open when they fail, and yours has failed and is stuck open The thermostat never closes, so cool coolant is always flowing through the engine. This is especially relevant on the interstate because the radiator cools the coolant much more effectively from the extra amount of cool air blowing in at higher speeds. Replace the thermostat to fix.

The specific problem with your transmission eludes me. I guess it's MAYBE possible (this is a big maybe) that the engine not getting up to full operating temp is affecting the temp of the transmission fluid and causing weird shifting. However, your transmission is electronically controlled and the engine temp technically shouldn't have any effect on it. If it was one of the older style centrifugal-force automatics, the temp might have some effect. In this case, if swapping out your thermostat doesn't magically fix it, ask someone qualified to give you a proper answer. I'd call a Toyota dealership service department and ask them. They might want you to bring it in, but on the other hand they might tell you what's causing the problem. You might try consulting a Hayne's or Chilton's manual for your car, too. If all else fails and no external reason can be found... it's time for a transmission rebuild.

Did the A/C blow cold last year? If so, the problem with your A/C can be attributed to two possibilities:

1. Low refrigerant due to a leak. Replace seals or leaking lines and recharge the system to fix. This is the cheapest possibility and should be tried first.
2. Dying A/C compressor. Replace A/C compressor to fix. If you recharge the system and there are no leaks it's definitely the compressor.

Good luck

[AHarris3719]

It's never been even close to cool. I tried refilling the refrigerant..used the can and it didn't lower the air temp even the slightest.

Would I have to replace the entire thermostat or just the sensor? Also, what is it called exactly? Thermostat Gauge?

[iToaster]

The transmission won't shift into 4th because there is a lockout until the engine warms up sufficiently, but because the thermostat is stuck open it never warms up enough to let it shift past 3rd. Changing the thermostat will fix that issue. It's called a thermostat, that's all that needs replacing.

[Sine Deviance]

Originally Posted by AHarris3719

It's never been even close to cool. I tried refilling the refrigerant..used the can and it didn't lower the air temp even the slightest.

Would I have to replace the entire thermostat or just the sensor? Also, what is it called exactly? Thermostat Gauge?

I think you're getting the thermostat confused with the temp gauge. The thermostat is a temperature-activated valve in the cooling line. The thermostat housing is on the front of the engine, on most cars it's where the upper radiator hose connects to the engine. I'm not sure about Corolla's because I haven't even looked yet Anyways, the thermostat is inside the housing. They are very cheap and very easy to replace yourself. Buy a Hayne's manual (~$15) and follow the instructions, it will be in the Cooling section.

If you tried refilling the refrigerant and you have no change, chances are you have a leak somewhere or your compressor is dying. Buy some UV refrigerant (it has dye in it so you can see leaks) and a leak detection kit (the kit comes with special glasses and a UV flashlight.) Put the UV refrigerant in the system while wearing the glasses and checking the lines with the flashlight. If you have a leak, you will see it. If no leaks can be found I'd check into compressors.

Originally Posted by iToaster

The transmission won't shift into 4th because there is a lockout until the engine warms up sufficiently, but because the thermostat is stuck open it never warms up enough to let it shift past 3rd. Changing the thermostat will fix that issue. It's called a thermostat, that's all that needs replacing.

Ah, I didn't know about the lockout. My thermostat is actually stuck open right now and mine shifts into 4th just fine, so I didn't think there was a connection.