6 to 12v conversion

[arcturus]

No info on that.I thought that some one might know that's why I posted photo of part number. My google search came to nothing.

[Ron Kwas]

Arcturus;

Simplest is to measure the current at 12V, then run the calculations at (https://www.sw-em.com/Vintage_Volvo_...ping_Resistors) for the R value, and use that value.

Bill M. also reports there he used a 0.6Ohm DR when he did his conversion.

Cheers

[Laird Scooby]

Originally Posted by arcturus

No info on that.I thought that some one might know that's why I posted photo of part number. My google search came to nothing.

Have you got an accurate ammeter at all? I don't mean the one in a multimeter, usually the range on them is too low.

If not there are other ways and means of working out the current, i just wanted the easy route first!

[arcturus]

Found this from Ron
nother more realistic example (I am told, that the single speed, PV444 6V wiper motor draws 5 Amps).

...more Kung-Fu:

Resistance = R = V / I = 6 / 5 = 1.2 Ω (Ohms)

Power = P = V X I = 6 X 5 = 30 Watts (a significant amount of heat!)
Just need to source a suitable resistor. Can you advise?

[Laird Scooby]

A 1.2 Ohm 50W (you always want the wattage to exceed the expected power by some margin) or 5x 6 Ohm 10W resistors in parallel. or 10 x 12 Ohm 5W resistors in parallel.

The neatest and as far as i can see, most cost effective way is this :

https://www.ebay.co.uk/itm/50W-0-1-8...s/183758297337

Select 1.2 Ohms from the drop-down and take CV-19 precautions for example spraying it with IsoPropyl Alcohol before using it.

[arcturus]

thanks,a big help. I'm totally useless with electrics and also number dyslexic. More than three digits and my brain turns to mush.
Will order two and connect in parallel to keep heat down,OK?

[Laird Scooby]

Originally Posted by arcturus

thanks,a big help. I'm totally useless with electrics and also number dyslexic. More than three digits and my brain turns to mush.
Will order two and connect in parallel to keep heat down,OK?

No, just one. Putting two in parallel will give you 0.6 Ohms. At 6A, that's only a 3.6V drop so assuming 14.4V charging voltage, that's 10.8V across the heater fan motor. That will make the motor very hot (so may improve the heating! ) but in time will burn it out.

If you really want to put two in parallel, get 2.4 Ohms as in parallel, it'll give you 1.2 Ohms.

The formula for equivalent resistance of resistors in parallel is (R1 x R2) / (R1 + R2).

For example, two 100 Ohm resistors in parallel (100 x 100) / (100 +100) = 10000 / 200 = 100/2 = 50 Ohms.

Funny things can happen when multiplying decimal point values so if you said 24 x 24 / 24 + 24 = 576/48 = 12 and then replace the decimal point you "lost" for convenience, it's 1.2 Ohms again.

[arcturus]

Thank's.head gone into tail spin

[arcturus]

What a b*****d,they wont ship to Portugal!

[Laird Scooby]

Originally Posted by arcturus

What a b*****d,they wont ship to Portugal!

Have you any relatives/friends in the UK that would be willing to receive said resistor and forward it to you?