AC Won't Turn Off

[TromboneAl]

Hi from St. Louis.

Trip still going great; I'll add some more to the blog in the next hour or two.

Noticed yesterday that the AC is on in our 02 Echo, even though switched off (with light off). This happened a few years ago, and it fixed itself after a short period.

Any suggestions on things to try? Locations to apply percussive maintenance?

If I can't fix it, I think that for the trip, I'll just pull out the AC fuse when I don't want it on.

Also, let's say I have the AC on but turn the temp dial up to a warmer temperature. Is it going to be using less energy?

Thanks,

Al

[jambo101]

Might be the clutch on the compessor is not disengaging percussive applications might prove fruitful.
I dont have air on my Echo but on my new Yaris the air comes on automatically if the vent selection knob is in the defrost position.

[REWahoo]

I'm enjoying your blog, Al. Keep up the good work.

No idea on why your A/C won't shut off - Midwestern culture shock maybe?

I don't believe you'll use less energy by turning up the temp on your car A/C. Unlike a home system which cycles the compressor on and off to regulate temp, an auto A/C accomplishes this by blending air from your heating system.

[Rambler]

If the clutch is not disengaging, I doubt that pulling the fuse will help. It would likely stay engaged.

Pretty much all Japanese cars with AC will engage the AC in defrost mode (as Jambo mentioned). Might want to check if the mode actually changed back to heat or vent when you twisted the knob to change it. I had a car that stuck in defrost mode once.

So very light percussion on the clutch when the car is off, or a few firm raps on the dash if you still have air coming from the defrost registers even after switching to heat or vent (try twisting the knob back and forth first).

I 2nd REWahoo on your blog...its great!

R

[Moemg]

I'm also enjoying the blog . I'm shocked you even have air in your car . What kind of spendthrift are you ? Plus this answers the DD car question .Give her the Echo and get a new car so your wife will not have to sleep in that tiny tent .

[travelover]

Quote:

Originally Posted by REWahoo ......................I don't believe you'll use less energy by turning up the temp on your car A/C. Unlike a home system which cycles the compressor on and off to regulate temp, an auto A/C accomplishes this by blending air from your heating system.

Not true on most cars, the AC does cycle on and off as needed to maintain pressure in the system.

On cars with an automatic temperature control, the AC cycles on and off to maintain pressure and the blend door dumps in heat from the heater core as needed. This is wasteful.

[TromboneAl]

Quote:

on my new Yaris the air comes on automatically if the vent selection knob is in the defrost position.

Wow, I bet that's it! I'll let you know, thanks!

Quote:

I'm shocked you even have air in your car .

A common refrain as we drive through the desert is DW saying "I'm glad I insisted that we get AC." I'm glad, too -- it's essential. I thought we wouldn't need it because at home the temperature rarely goes above 60. This trip would have been torture without AC.

[REWahoo]

Quote:

Originally Posted by travelover Not true on most cars, the AC does cycle on and off as needed to maintain pressure in the system.

I agree - the compressor in a car cycles on and off to maintain pressure, but I'm not aware that it cycled to regulate temperature. I think regulating temperature is done by adding or taking away heat into the airflow.

Quote:

Originally Posted by travelover On cars with an automatic temperature control, the AC cycles on and off to maintain pressure and the blend door dumps in heat from the heater core as needed.

I believe the same holds true of cars without automatic temperature control. When you turn the AC to a warmer setting on a manual system, you are opening the mix door to allow in more heat.

But hey, I'm an investment expert, not an auto mechanic...

[travelover]

Quote:

Originally Posted by REWahoo I agree - the compressor in a car cycles on and off to maintain pressure, but I'm not aware that it cycled to regulate temperature. I think regulating temperature is done by adding or taking away heat into the airflow. I believe the same holds true of cars without automatic temperature control. When you turn the AC to a warmer setting on a manual system, you are opening the mix door to allow in more heat. But hey, I'm an investment expert, not an auto mechanic...

Right, we're down to semantics now. What you described is correct.

[HFWR]

The switch probably activates a relay, which may be sticking. Or not...

[NW-Bound]

Quote:

Originally Posted by TromboneAl C is on in our 02 Echo, even though switched off (with light off). This happened a few years ago, and it fixed itself after a short period. Any suggestions on things to try? Locations to apply percussive maintenance? Al

Quote:

Originally Posted by HFWR The switch probably activates a relay, which may be sticking. Or not...

The same thing happened in my car some time ago. Under the hood was a relay rack. Knocking on the square relay can that controlled the AC compressor clutch and the condenser fan did the trick, using the handle of a screwdriver. Has not happened since. It appeared that the relay contacts fused together and needed a bit of persuasion to let go of each other.

[TromboneAl]

Quote:

the air comes on automatically if the vent selection knob is in the defrost position.

That was indeed it. I turned it away from defrost, and the AC went off. I've just never run defrost without the heat all the way up before.

Many thanks, Jambo!

[Sue J]

My husband had the same situation in his 2001 Corolla. I asked about it at the Toyota dealer. It's not a defect, it's a feature!

[travelover]

Quote:

Originally Posted by Sue J My husband had the same situation in his 2001 Corolla. I asked about it at the Toyota dealer. It's not a defect, it's a feature!

As far as I know, this is true for all cars. Generally the failure mode (vacuum failure, for instance) for the climate control system is to go to defrost mode, as a safety feature.

[Martha]

When we come down the hill to the big lake in the summer our windows often fog due to the temperature change. We run the defroster to dry out the windshield. On all of our vehicles the air comes on with the defroster. I think the purpose is to remove the humidity.