Right, had some time in the garage this afternoon – football on the radio, tea in a Thermos, the smell of woodsmoke wafting in through the gaps in the roof
First of all I hooked up the fan to the defibrillator to check that the thing actually worked and gave myself a surprise as it almost spun itself off the workbench … they’ve got quite some kick to them on startup.
To see what the “current draw” of the fan is, I resorted to reading the instruction book for the multimeter as I finished off a cuppa and a couple of fruit shortcakes
Maybe someone can interpret the reading for me, and tell me what it means in the real world?
It doesn’t appear to be the most efficient fan blade design in history – with the generated airflow seeming to be two-thirds out the back and one-third out the front – but what it lacks in sophistication will, I believe, be made up for in brute force cooling. It certainly seems to shift more air than the viscous unit anyway
I noticed on the way back from Oulton Park last week that the brake lights didn’t seem to be working I’d got an advisory for this being intermittent on the first MOT some 15 months ago, so thought I’d best get something done about it now it’d gone completely Intermotor part number 51500 is the brake light switch you want.
It fits onto a bracket above the brake pedal and when the pedal is at rest, the white plunger on the switch is pushed in and the lighting circuit is broken – so the light isn’t on. When you press the brake pedal, the arm goes down, the plunger in the switch comes out, the circuit’s made and, hey presto, the brake lights come on The hardest part about changing it is twisting your body round to get underneath the pedals to wave the spanners about
EDIT 26/01/08 :
merp0 : Good work Stu, aided by tea and biscuits. I can’t remember exactly, but aren’t RS Turbo fans mounted on the back of the rad., and therefore suck. But does this really matter, can’t you just reverse the direction of rotation of the fan. Thinking aloud here, somebody put me right.
Graham : stu i cant quite make out which setting you have your ammeter on looking at the dial it appears to be on AC amps, you need DC or you wont get a sensable reading.
electric fans are more efficent when mounted behind the rad, most fan blades are directional so simply reverseing the polarity of the motor to try and change the direction the fan blows in results in a very inefficent fan.
viscous fans are always turning with the engine running although they slip so they are not turning anywhere near as fast as the engine until the center of them gets hot then they should progressively lock up
me : Ha ha, erm … I was going to make up something clever to put here about the light reflecting funny off the dry-wipe board on the wall and distorting the readout as it appeared in the final picture … but truth is it was on the wrong setting At the time I was just happy the fan was going round and didn’t notice
This next shot is with the positive (assuming of course that the red lead coming out of the defibrillator is the positive – as that’s what it would get connected to on the battery were I jumping the car) connected to the brown wire on the fan …
And this one is with the positive connected to the black wire on the fan …
You can probably tell at this point that electrics aren’t really my forte … but as with other stuff, I’m quite happy to learn in public Anyone who’s prepared to help along the way … I thank you
dangerousdave : Stu they sit in front of the rads on rst’s, you must have seen at least 10 rs’s with the cd behind the grille slipped onto the front of the fan unit
Also i think brown is fords earth colour, it is in my gti! And black therefore would be positive
Graham : normally electrically the current flow would be the same which ever way you connected the wires, however if you get a higher amp reading this way round then the motor must be working harder and so the the fan shifting more air so that would be the correct way to wire it up
after saving and playing with your pictures i think i made out that the ammeter was showing the fan drawing 10.5 amps in which case id fit a 20A fuse, although you probably would be alright with a 15A
if you fit a fuse too close in rating to what an appliance uses, the surge from it keep starting up will pop the fuse every so often as fuses dont really like repeatedly working close to there maxium load capacity.
take EFI fuel pumps for instance, most car manufacturers fuse them with either a 10 or 15amp fuse but if you check the amps the pumps draw its usually about 5A
me : Sorry if it wasn’t clear – 8.59A one way and 10.56A the other … I tried each setup three times and the readings were pretty much the same each time. The multimeter showed it spiking to about 18 amps on initial startup, whichever way round it was wired, so I’ll go with your suggestions of a 20A fuse and a 30A relay.
mk1matt : Definatly a blower not a sucker and so goes in front of the rad
me : That’s a relief – I was as chuffed with my brackets as Slartibartfast was with his fjords