mk 2 petrol sender unit wanted

[BusyKiwi]

me again

This conversion I've done on the standard van (OZ beddie running gear in UK beddie) has been very educational

I've found out (I think) the mk 1 and mk 2 petrol tank sender units are different - how different, they work opposite to each other.

So if anyone has a spare mk 2 sender unit they would like to swap, sell, give away or swap please let me know.

Thanks

[Bas NZ]

Busy, I had one in a complete tank in the spare van I got for parts but dumped it with the van, who would think of kepping that.

[BusyKiwi]

I did the same thing

[Rogue Trooper]

I'll be swapping mine out before too long as the Fairmont electric pump I'm fitting has the sender built into the unit so the Bedford one will probably be superfluous. Just need to find someone who welds fuel tanks.

If you don't find one I'll bear you in mind when I remove it.

Ta

[Rogue Trooper]

I've been thinking about this and it seems a bit strange. I thought the sender units were just a variable resistive load. The more resistance on the sender the less juice you have in the tank. If they were different I would have thought there would have been a lot more people having trouble with their dash conversions over the years. I know I didn't have any trouble with my first one.

It's not something silly like you have the polarity reversed on the back of the gauge? It would be a DC coil so is polarity conscious.

Sorry if this is telling you how to suck eggs.

[BusyKiwi]

I took the sender, gauge and resistor out of the van and tested on the bench. They all work separately but not together.

The problem is the sender, the normal sender works between 240 to 33ohms (33 ohms full) but what is needed is a sender that works the opposite, 10 to 180 ohms (180 ohms full)

The polarity can't be reversed (checked all that) as they are run in series not parallel as needed for this sender.
I can wire it in parallel to suit everything but the resistor needed wouldn't stop a spark in the sender which could create a big boom.

The hanes manual says if the fuel gauge reads full all the time it could be a broken or unplugged wire, which I believe is a misprint as the sender goes to one side of the gauge with the other side coming from the resistor (which also goes to temp gauge), this would be true if wired parallel but isn't.   

I wish it was something simple like crossed wires. I've never come across this before, actually have never seen a sender unit float like this one, is a round ball type instead of the usual cylinder shape

The wiring diagram I've been using is on 292/293 of the hanes bedford manual

thanks for trying

[Rogue Trooper]

Sorry but that doesn't sound right to me.

Regardless of whether it is in parallel or series the polarity can still be reversed if it is a DC circuit. AC is a different matter entirely.

You're talking about the resistor and the sender being seperate. Is there a resistive load behind the dash as well on the feed wire coming from the positive supply?

Just checked the manual and the resistance value of the sender should range between 1 and 30 ohms. If you're getting 240 ohms that could be an indication that something is not quite right somewhere.

Just checked the Fairmont one because I can and the sender gives a range of 2 through to 175 ohms. Can't get to the CF one as it's still in the van and I don't want to pull it out just yet because I have too many other parts already lying around. I would suggest that if one of the resistance values you are getting when you test the sender isn't very close to 1 ohm then that is where the problem lies.

Can't see the fuel gauge circuit on pages 292/293. I would be looking at either 288/289 or 296/297 assuming we are looking at the same manual.

[BusyKiwi]

I haven't got my book with me at the moment so can't check those pages.

I've included a diagram of what works and whats in the book. the top one is the books version but my gauge reads full all the time on this system. the second is how it works but works at about 6v so would need another resistor to drop it to that ...

I didn't draw the contents, sparkie mate did, as well as testing all the bits

[BusyKiwi]

sorry it's not a resistor, its a voltage stabilizer

[Rogue Trooper]

That sounds better. I remember that voltage stabiliser now. Caused all sorts of flakey issues for those who had lost them.

That top diagram looks right to me. The parallel circuit below would not be correct. Looks like your sparkie mate has it right with the 0 - 50 ohms on the sender. It sounds to me like you might have too much resistance in the circuit somewhere.

You wouldn't want to use a resistor to drop voltage either. That affects the current flow as voltage is a product of both current and resistance. Diodes in series are a much better way as they only drop voltage across them and don't affect the current. A standard power diode drops 0.7v.