# heater resistor

Discussion in 'General Electronics Chat' started by Webby, Jul 31, 2008.

1. ### Webby Thread Starter Active Member

Jun 15, 2008
66
0
Hi all, got a query with a heater resistor from a motor vehicle which is used to drop the voltage at the heater motor to give you 4 different speeds.

The heater resistor has 3 resistors in series how can I calculate the individual resistor values dont know if they are all the same or a different value. I suspect they are all the same resistors.

Do I just take the total resistace and divide by 3?

Here are some attachments of the heater resistor and tests carried out.

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• ###### 1.5ohms.jpg
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Last edited: Aug 10, 2008
2. ### scubasteve_911 Senior Member

Dec 27, 2007
1,202
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Resistance adds in series, and divides (when equal) when in parallel.

So, if four 10 ohm resistors in series, then 40 ohms total. If four 10 ohm resistors in parallel, then 2.5 ohms.

Steve

3. ### Webby Thread Starter Active Member

Jun 15, 2008
66
0
Thanks for that, thats what i thought in series just add all the resistors together to get the total. Ive added some pictures where i have used my meter to find out the individual resistor values. Being as i think there wired in series surly i can measure the total resistor value some how? Without having to measure individual component values.

4. ### cumesoftware Senior Member

Apr 27, 2007
1,330
11
For that, you just need to wire them in series or in parallel (as you wish) and measure the resistance of the resistor association with the multimeter the same way as you would measure any other resistor.

5. ### Webby Thread Starter Active Member

Jun 15, 2008
66
0
Hi, what I mean apporantly the heater resistor is designed with the resistors wired in series. When I measure I cant seem to find where I can measure the total resistance all I have managed to do is measure individual resistor values am I doing something wrong or is this not possible?

I would of thought this was capable of doing i.e from the picture I took we have a 1ohm,2ohm and 1.5ohm resistors =4.5ohms surly I should be able to measure this some how?