[Mk2] [Turbo] Stef Derner Speedo Converter

[Shmed]

Does anyone have any details about these or know if Stef is still about?

Cheers

[dantheman]

i use one, might be able to help. Whats the problem?

[Shmed]

I bought the 180 mph clocks off someone on here (can't remember who), and they came with the converter attached. When I first plugged them up to my car, the speedo needle did the two step test procedure, and then all worked fine.

Before the car went off the road 18 months ago, the speedo had stopped working, and I presumed it to be the speed sender unit in the gearbox.

I've bought a new sender, but as I was thinking about it and reading other posts on here, I realised that the speedo doesn't do the two step test any more and kind of thought that perhaps it's the converter rather than the sender.

From what I understand, there are some dip switches on the converter that 'tell' it to do the test sweep at power on and I need to check that they are still set to test, but I guess what I need to know is, should the gauge do the self test all the time, whether the sender is working or not?

I also wondered if anyone knew of any continuity/electrical tests I could do on the converter to check it out?

Cheers

[dantheman]

have a look here, see if it helps: http://www.imoc.co.uk/forums/viewtopic. ... highlight=

You turn the test procedure on or off by switching the kph/mph switch from 1 point to the other whilst ignition is on. mine did the test even when the speedo wasnt working properly.

one thing i would check is the gauge cluster itself. either swap it for another unit and see if that works or check that the circuitry is all intact. my clamping delimiter wore through the lightbulb wire circuit causing no backlighting. Maybe you have the same problem but with another circuit.

[Slarty]

To rule the convertor out of the equation you can simply unscrew the 4 phillips screws and remove the unit. You'll be back to sqaure one then.

I'm sure Stef is still about though, have you tried pm'ing him?

[asdrewq]

Once you realise the dial sweep counts up the odometer by about 0.1 miles each time you will want to turn it off anyway

[Shmed]

Right, I have actually tried to fix this now, and came up with the following (with the help of the link posted by Dan):

Of the four screws, two 'continue' the circuit from the plastic flexi circuit board on the rear of the dials through the delimiter and straight into the back of the gauge. They are the bottom two screws on the delimiter 12v and earth. Lets call these the straight through connectors.

The top left screw seems to be a piggy back connector in that it takes the signal from the flexi circuit, changes it, then sends it on to the gauge (thus tricking it to read in mph or kph).

Now the top right one seems to be the one that is causing me some confusion. It is meant to carry the 5V signal to the ECU to sort out fuel cut, PAS and other speed related things, but I get no continuity between the screw through the delimiter and the plastic flexi, so there is no way it can tell the ecu the speed. Is it meant to have continuity?

I have also noticed that mine seems to read 10.97V on the top left screw on the delimiter, even if I switch on test mode. This doesn't seem right?

I can't generally get the needle to do anything, but if I can get the test mode to 'try' and work (by wiggling around the top left screw, it goes 40, then 85, then 0, which, even if the speeds weren't relevant, is nothing like going 120, then 60 then 0.

So, does anyone know:

1. Should the top left screw voltage be 10.97v?
2. Should there be continuity between the top right screw and the purple and silver/white ECU signal wire?
3. Should there be continuity between the top left screw and the purple wire (I think this is one that shouldn't have continuity)?

All locations of screws are based on looking at the speedo/delimiter from the back of the dash.

[dantheman]

i seem to recall when i did my tests i had a pretty flat battery. So if i was getting 9.5V with a low battery then i imagine 11V with a full battery is correct.

I did do a test where i took a piece of wire and bridged some of the screws together, possibly top left and bottom right? That made the speedo needle bounce around.

[Shmed]

did yours do the test sequence? I think my problem is between the delimiter and the actual speedo, but could be wrong.

[dantheman]

yes it did

[Shmed]

What was the problem with yours in the end?

[Stef Derner]

The top right screw brings the modified signal from the speedo if no delimiter is fitted. If the signal into the speedo is converted to MPH then you don't want the signal out of the speedo to go to the ECU so the screw is isolated from the flexi PCB/ECU by the delimiter, which sends it's own KMPH signal to the ECU. Don't worry about the top right screw, what you are getting is correct.

Check the delimiter board where the copper wavy washers are soldered on, if the solder squeezes out under the washer, it can cause a short to the screw and stop the unit from working so make sure there is no solder between the inside of the washer, getting close to the hole where it may touch the screw.

On the flexi PCB, check the two solder bumps under the delimiter, if they break through the insulation on the back of the delimiter, that can stop it working too. You can always replace the insulation with a few layers of insulating tape.

Keep me posted.

[Shmed]

Check the delimiter board where the copper wavy washers are soldered on, if the solder squeezes out under the washer, it can cause a short to the screw and stop the unit from working so make sure there is no solder between the inside of the washer, getting close to the hole where it may touch the screw.

Cheers Stef, I will be checking that ^ next chance I get. It makes sense that the issue is there. I did notice that when the top left screw was loose, I got some reaction on the speedo when I wiggled the screw, so a short there makes sense.

Will let you know

[dantheman]

What was the problem with yours in the end?

I never found out. I crashed that car, fitted the same set of gauges to a new car and it worked fine.

[Shmed]

Maybe that's the answer, I'll go and crash this one and buy another

[Shmed]

Still not had chance to actually look at it, but remembered I took some pics.


The bit of solder at the top of the top hole looks like it might come close to shorting on the screw.



Should I push the screw through the hole and check for continuity from the screw to the wavy washer?

I have a desolder tool, but am a bit unsure about taking a soldering iron to it.

[Shmed]

Just checked continuity between the top left screw and the flexi pcb on the back of the dials (should show continuity if it is shorting) and it doesn't. Screwed it back on and it did the proper sweep test (120 then 60), but it only works when switched to kph

[Shmed]

weirdly, with the switch set to kph, the speedo works fine (and reads in mph as verified by my GPS speedo).