climate control simple test
Thread Starter
Joined: Feb 2006
Posts: 7
climate control simple test
I use a real simple test to make sure my climate control is up to snuff from time to time.
My car is a 1983 300D with gobs of miles on it.
I use this test anytime the car is in a heat or AC mode, and I'm driving along.
If I'm drinking a soft drink, I can place the cup on top of the small dashboard sensor grill for less than 30 seconds. The sensor draws the cold air generated by the bottom of the cold cup to the thermostat, and will respond by increasing the blower motor speed, and will re-direct the heat by shifting to the correct nozzles. In other words, it thinks the cabin is cold, and cranks up the heat.
If I'm drinking a coffee, I can do the same to shutoff the heat entirely, or to turn on the A/C system if in the "non economy" mode. Now the climate control thinks it's hot in the car interior, and wants to drastically cool it down.
After removing the cup, the climate control will go back to "normal" after a short time delay.
This doesn't work well with a paper cup with an indented base on the cup, or doesn't work at all with an insulated cup. Try it with a plastic cup with a smooth base.
You can perform this test in any season, or in any outdoor temp situation. Remember to wait until the engine is warm enough to generate heat, and also remember the A/C compressor will take a few minutes to really crank out cold air. Merely leave the cup on the sensor long enough to do the test to your satisfaction.
Have fun testing!
My car is a 1983 300D with gobs of miles on it.
I use this test anytime the car is in a heat or AC mode, and I'm driving along.
If I'm drinking a soft drink, I can place the cup on top of the small dashboard sensor grill for less than 30 seconds. The sensor draws the cold air generated by the bottom of the cold cup to the thermostat, and will respond by increasing the blower motor speed, and will re-direct the heat by shifting to the correct nozzles. In other words, it thinks the cabin is cold, and cranks up the heat.
If I'm drinking a coffee, I can do the same to shutoff the heat entirely, or to turn on the A/C system if in the "non economy" mode. Now the climate control thinks it's hot in the car interior, and wants to drastically cool it down.
After removing the cup, the climate control will go back to "normal" after a short time delay.
This doesn't work well with a paper cup with an indented base on the cup, or doesn't work at all with an insulated cup. Try it with a plastic cup with a smooth base.
You can perform this test in any season, or in any outdoor temp situation. Remember to wait until the engine is warm enough to generate heat, and also remember the A/C compressor will take a few minutes to really crank out cold air. Merely leave the cup on the sensor long enough to do the test to your satisfaction.
Have fun testing!
Senior Member
Joined: May 2004
Posts: 1,582
From: CHICOPEE
RE: climate control simple test
I just got the heat and AC working on my 79 450SLC, I bought the car last October. between vacuum leaks, a bad amp and servo, and $$$ it is working. I am going to try your test, as I get heat, but have to keep the temp dial at 85 in the cold, cold weather. I am thinking of bleeding the sytem again, as I see the anti freez is down so it it flowing thru the heater core and all that stuff. But is the ambient sensor you speak of is not working correctly the whole chain is messed up. There is another test. Take a paper tissue and hold it over the sensor, if it is working properly, the sensor will act like a vacuum cleaner and pull at the tissue.
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