Using the heat when it's cold... mpg drain?

[orange4boy]

Try throwing an insulating blanket over the window over night. Try it with a regular blanket if you don't have the bubble wrap with foil type. To reduce condensation you have to either reduce the moisture in your car or warm up the glass a bit so the moisture does not condensate at all. Think of it like double glazing only the insulating layer is a blanket not another layer of glass. This also works to keep off frost. I had good success with keeping off frost with just a foil blanket held on with some rare earth magnets.

[micondie]

I think many cars use resistors in the blower circuit to reduce the speed of the blower. If this is the case then the blower will use the same amount of electricity on all settings. On the slower speeds you will just have electric heat. The resistors are usually in the heater duct.

[PaleMelanesian]

I've measured my blower, and the power draw is proportional to the speed setting - low speed uses less than high speed. Sitting with the engine off, reading battery voltage, and each higher setting drops the voltage another 0.1. Back to a lower setting and that 0.1 comes back. I'm not sure about the why or how, though.

Volts - Fan setting
12.2 - Off
12.1 - 1
12.0 - 2
11.9 - 3
11.8 - 4

[micondie]

Originally Posted by PaleMelanesian

I've measured my blower, and the power draw is proportional to the speed setting - low speed uses less than high speed. Sitting with the engine off, reading battery voltage, and each higher setting drops the voltage another 0.1. Back to a lower setting and that 0.1 comes back. I'm not sure about the why or how, though.

If you are just reading voltage then you haven't measured the power used. You have to measure amperage too. Amps X Volts = Watts (power)

[PaleMelanesian]

To be technical, yes. However, when you draw more current from a lead-acid battery, it's voltage drops. This is an indirect and easy way to compare one setting against another. I don't know how much current it's drawing. I do know that the fan on setting 3 draws more than on setting 2. That's my point, that there is a difference.

[Daox]

Pale is correct. Darin tested this a while ago.

Watts . Item
30 heater fan low speed (1)
49 heater fan 2
66 heater fan 3
81 heater fan high (4)

From: Tested: power draw of Geo Metro accessories & systems (volts, current/amps, watts)


Since I run with my alternator disabled, and now that it is fairly cold in the morning, I'm still very careful about using the fan. As Darin found out, his fan can consume more power than his car requires to run the engine! That, plus the addition of using headlights is a large drain to the battery. If I can avoid it, I don't use it.

[jamesqf]

Originally Posted by micondie

I think many cars use resistors in the blower circuit to reduce the speed of the blower. If this is the case then the blower will use the same amount of electricity on all settings.

Resistors don't work that way. They're not "burning up" the extra electricity, they're more like valves that just let a certain amount through.

[micondie]

The resistors used in heater circuits are coils of resistance wire which are placed in the heater duct to dissipate the heat they generate and eliminate the possibility of melting/burning something. (like fingers)

[Frank Lee]

What?

[greasemonkee]

Since current is constant through the entire series circuit, the resistors are in fact "burning up" wattage, they're burning up voltage to be specific.

A resistor is not a transistor.