Team-BHP - Does heater consume engine power?

:OT Is it true that windshield will crack if we use defog when AC is on.

My friend use to warn me not to use defog when the AC is running. Reason being - due to the temperature difference in the cabin and the windshield surface.

Has anyone experienced this problem...?

this problem was reported by a dude from jallandhar(Punjab).
He drove his Indigo from the showroom and switched on defrost. The rear glass shattered.
Got replaced under warranty. Again this things happened. the workshop replaced the glass again under warranty and did some checking with the system which was found to be faulty. the problem did not come again.
though he was happy with Tata service, he wrote to autocar about this problem. Looks like the problem was due to defective defrosting system.

As for the temp difference argument. On a cold foggy winter morning, the outside temp would be something like 3-4 degrees, and inside the car it would be 10 degrees or so. Its in such conditions when rear defogging is used, the rear windshield temp would rise.

With AC on the inside temp would be something like 10 degrees too as below that ACs cut off. So that does not bite. Unless you have a defective defrosting system which changes the glass temp too rapidly, your laminated glass should not crack.

Quote:

Originally Posted by Shan2nu

I don't think so. Infact, you don't need the AC compressor to produce heat. My guess is that the heat produced by the engine is used to warm up the cabin.

I've seen race vids where drivers switch on the heater if they feel that the engine temp is risen beyond normal.

To confirm my theory, try switching on the heater when you start the car for the first time in the morn. You maynot get hot air instantly. The engine will have to warm up before this happens.

Shan2nu

agree: 100%,thats the same theory as mine.

Quote:

Originally Posted by tsk1979

well with tata cars everything is possible,they are so superbly misengineered.lol:

Quote:

Originally Posted by Rehaan

Well if this is true, theres a slight possibility that the extra current drawn by the electric blower is causing this. (the same would happen if you turned the fan on in AC mode without the compressor on (ie AC switch off))

cya
R

I agree with Rehaan. If you feel a drop in power, it is probably because of the power drawn by the fans. Try switching the fans off and see what happens.

Quote:

Originally Posted by cnu

There is absolutely no harm in using the heater when the AC is ON. In fact there is nothing like switching ON the heater except for switching on the fan and the adjusting the air control knob. You have two vents for the air flow into the cabin - one for the cool air and the other for the hot air. The air control knob controls the opening of these two vents and hence based on the position of the knob you get a mix of cold and hot air.

Agree with you
you can infact use heater knob to manually adjust cabin temprature with AC ON