Heater speed control (Plus 2)

[PeterK]

On the left side (as you sit in the car) of the heater unit, there is a 'thing'. This 'thing' has the wires from the switch and to the motor, so I assume that it is a resistor of some sort / size to reduce the motor speed (low/slow speed option).

It is just visible in the parts manual, but not mentioned (that I can see / find anyway), Susan (Mick Miller) doesn't stock them and they are not on the SJS website.

Are they available from anywhere, and if not and are just a resistor, does anyone know what resistance they should be please

Thx
Peter

[spridget]

Hi Peter
Yes the " thing" is a resistor. 2 postive wires are coming from the switch : one is connected on the terminal where the heater is connected : for the high speed. The second positive wire is connected on the other terminal of the resistor that gives the slow speed.
Franck

[andyhodg]

Hi
I had to replace mine because it stopped working. I could not find a like for like replacement and ended up replacing it with two wire wound resitors from Maplins. I can't remember the exact details but I bought 2 approx. 4 ohm resistors that I connected in parallel. The reaon for two in parallel was to increase the power handling capability. The overall resistance was approx 2 ohms and it has worked well since I installed them. I soldered the bare resistor wires together with the motor/switch wire.

I secured it all in place by using tie wraps and self-adhesive tie wrap bases securing the ends of the resistor wires to the side of the heater.

Good luck

Andy

[PeterK]

Thanks Andy, Maplin here I come

[rjaxe]

Peter, if you want to preserve the circuit originality you could try refurbishing the unit. The unit I had suffered from corrosion under the connections. I drilled out the holding rivets, cleaned it all up, re-assembled with copper rivets and it now works fine.

[PeterK]

Unfortunately the fine elements are broken in several places, so refurbishment does not look possible

[Gordon Sauer]

I bought one of these off eBay I believe from a general Lucas supplier type person of new old stock. The number is 47196. That's the number that's printed on the box and also the number that is stamped into the device. Gordon Sauer

[PeterK]

Will try one of these http://www.ebay.co.uk/itm/130801720165?var=430106051305&ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
Big power rating as I don't like the idea of hot things behind the dash in a f/g body
Peter

[andyhodg]

Hi Peter

I wish i had found that when I did mine it looks ideal. My resistors don't get too hot when in use. I can touch them with my fingers my guess would be about 55 deg. C.

Regards

Andy

[Gordon Sauer]

On the NOS 47196 Lucas unit that's out of the car looks to be 2 ohm resistance Gordon Sauer

[PeterK]

Thanks Gordon. I've ordered 2.2R as that's the closest I could get, following Andy's suggested sizing

[vernon.taylor]

Salut

Whatever you use if you can still touch it and not get 3rd degree, that's fine.

More scientific : you need to measure the voltage drop across the resistor in circuit. The power developed is equal to the voltage squared divided by the resistance. You should use a resistance with a power rating of at least twice this result.

To note the eBay resistor and others clad in aluminium (which should be available from Maplins/Radiospares and others) has a 50W rating when on a suitable heatsink. If you want to be really sure you could mount the resistor on a suitable place on the heater box with self tappers - ideally metal-to-metal and with a heatsink compound (costs pennies). If the heater box is grounded make sure your connections are well-insulated.

@+

Vernon

[PeterK]

Salut Vernon
My plan is to mount the resistor on the heater casing, where the old one was located
Peter