MFI speed switch

nickphillips · Post by **nickphillips** » Mon May 14, 2007 11:05 am

Mike

This may have been mentioned, try this link, ccrt diagram of the speed switch,
http://forums.pelicanparts.com/showthre ... adid=78685.

It uses mainly discrete component that could be checked with a dvm.

cheers

nick

impmad2000 · Post by **impmad2000** » Mon May 14, 2007 11:23 am

Thanks for that Nick,
I was trying to figure out the circuit schematic the other evening but just gave up !! These things are totally repairable Mike

Tim

210bhp · Post by **210bhp** » Mon May 14, 2007 4:32 pm

Thanks guys.
I think I must have read every thread and link on Pelican on MFI including that one. The problem is that I am sure the speed switch is faulty (and thanks to others on this board I will find out in the next day or two) but nowhere do I find a definitive way of going about testing the board or it's components (for an electronics amateur like me). Does this involve special equipment or could I do it?

I took the circuit board out again yesterday and checked it under magnification and could not find a single obious defect in the connections. Some say they break. others say they can rust out and that can leave bits floating around in the box. Mine looks as clean as a whistle so if it is faulty must be a failed component?

It's all very well having a detailed circuit diagram but how do you test what each bit is supposed to be doing?

Any comments welcome.

Regards
Mike

nickphillips · Post by **nickphillips** » Mon May 14, 2007 5:08 pm

Mike

You really need somone who has had some basic electronic experience, you need a DVM (digital multimeter) to start with, you can check the resistor vaules, diodes and transistors. Will you be at the next MB masterclass?. I could bring my DVM??.

Cheers

Nick

210bhp · Post by **210bhp** » Mon May 14, 2007 5:58 pm

Nick

Yes I will be at the next masterclass. If you could bring your thingumyjigywhatdoyoumacallit that would be great!

I will let you know how I get on this week with a replacement unit.

Cheers
Regards
Mike

impmad2000 · Post by **impmad2000** » Mon May 14, 2007 6:47 pm

On one of those links, Early S Man has a diagram for a suitable piece of kit, some diodes, 12V transformer and a reed relay. He calls it his tacho calibrator, but the also mentions it wrt testing the speed switch. The values you'd get are slightly different here in the UK as we have 50Hz mains and not 60 Hz, hence we'd get 1000rpm and 2000rpm instead.
Some small transformer bricks have AC out, use one of these and some diodes and hey presto. I'd post a link to the pelican circuit, but I can't get on at the moment.
Cheers
Tim

impmad2000 · Post by **impmad2000** » Mon May 14, 2007 8:20 pm

Yay, I've fixed mine

I'll post it up anyway Mike. It was just a dry joint. Yours is probably exactly the same. I found if i wiggled the relay it would operate (with suitable input of course. ) Just go aorund the back of the pcb with some fresh solder and a soldering iron. It just may work

always nice to fix things

Tim

210bhp · Post by **210bhp** » Tue May 15, 2007 10:17 pm

Update

Thanks to everyone for your help and info.

A substitute speed switch installed tonight and everything works perfectly so far. I took the oportunity to clean up contacts while I had things apart.
Going to go for a longer road test tomorrow night and then recheck adjustments etc. If all is well I will change the oil in readyness for the Scottish run.

I will be looking for pointers to check and fix the the old switch so still need your help Tim and Nige.

Thanks again

Regards
Mike

210bhp · Post by **210bhp** » Thu May 17, 2007 8:44 pm

Further update

Many thanks to Andy and Tim. Both sent me spare switches, both of which work perfectly. Andy's is on loan and Tim insists I can have his without charge which is incredibly generous. At his suggestion I would like to make a donation to the MacMillan Nurses as a big thank you. Can anyone tell me if I can paypal this and where, or do I send a cheque to someone on this board? Or has someone an address?

This is DDK at it's best

Thanks to all

Regards
Mike

hot66 · Post by **hot66** » Thu May 17, 2007 9:38 pm

Contact Barry for the Donation. I have just paypal'd him the donation from our Masterclass @ MB-porsche engineering

impmad2000 · Post by **impmad2000** » Thu May 17, 2007 10:00 pm

I'm pleased it works for you.
Cheers
Tim

210bhp · Post by **210bhp** » Fri May 18, 2007 12:10 am

Donation made to MacMillan

Now to try to fix the old switch

Thanks to all

Regards
Mike