27 replies to this topic

[taffy1967]

For the two gauges I took a live feed from the last blade of the fuse box as it goes live with the lights.

That could be you're problem mate, because you've attached them to the same circuit as you're instruments.

So try removing the spade connector you fitted for those gauges and test drive you're Mini to see if you're temp/fuel gauges behave normally again.

Edited by taffy1967, 20 February 2007 - 07:33 PM.

[Big_Adam]

I will do. Think is, it's all a bit temperamental. I went for a drive when this all started and everything was fine. Then the gauges decided to fly up to high on the petrol and max on the temp.

I'll pull it off tommrow tho. See what happens.

[taffy1967]

It's definitely worth a try and to be honest i'd imagine if you're voltage stabiliser was at fault then you're gauges would either not read at all, or misread all the time, not behave erratically like that.

So it does sound like something else is affecting them and it's possible that you're voltage stabiliser is getting some kind of electrical feedback from you're auxilliary gauges when they start to kick in, because their connected via the same circuit.

Well it's possible and like I said before, the wiper motor park-switch used to make that bottom fuse blow on my Mini when it failed and caused a short circuit.

But on my sister Mini (her's didn't have a tachometer), the fuel gauge used to read full. However if I sprayed WD40 at the rear of the wiper motor (effectively coating the park-switch), then the gauge would read correctly again for quite some time. Replacing the park-switch cured the fault in both our cases of course.

So I guess the gauges and voltage stabiliser are very sensitive?

Edited by taffy1967, 20 February 2007 - 08:40 PM.

[dklawson]

" For the two gauges I took a live feed from the last blade of the fuse box as it goes live with the lights. "

OK, I'm still at a loss. You identified what the gauges were but not what's going wrong with them... apart from reading high. However, from the end of your last post it sounds like you're operating the gauges without a stabilizer at the moment. Is that correct? If so, they will drift up and down with the alternator output and they WILL read as much as 40% too high.

For reference when you have the stabilizer in place, your switched 12V from wherever (fuse box or elsewhere) goes to the "B" (for battery) terminal on the stabilizer. The "I" terminal on the stabilizer goes out to the instruments. Again, without the stabilizer, or if you wire it wrong, you can supply the gauges with system voltage (sometimes over 14V) which is well above the stabilizer's 10V output. This will make the gauges read way to high... and it can burn the gauges out over time.

[Big_Adam]

So it does sound like something else is affecting them and it's possible that you're voltage stabiliser is getting some kind of electrical feedback from you're auxilliary gauges when they start to kick in, because their connected via the same circuit.

Well it's possible and like I said before, the wiper motor park-switch used to make that bottom fuse blow on my Mini when it failed and caused a short circuit.

I will have a look at the wiper motor when I get a chance. But this whole mess started with the damn stereo. The auxilliary gauges only pull lighting power from the bottom fuse tho. As I only need light for them. Their both mechanical past that.

" For the two gauges I took a live feed from the last blade of the fuse box as it goes live with the lights. "

OK, I'm still at a loss. You identified what the gauges were but not what's going wrong with them... apart from reading high. However, from the end of your last post it sounds like you're operating the gauges without a stabilizer at the moment. Is that correct? If so, they will drift up and down with the alternator output and they WILL read as much as 40% too high.

For reference when you have the stabilizer in place, your switched 12V from wherever (fuse box or elsewhere) goes to the "B" (for battery) terminal on the stabilizer. The "I" terminal on the stabilizer goes out to the instruments. Again, without the stabilizer, or if you wire it wrong, you can supply the gauges with system voltage (sometimes over 14V) which is well above the stabilizer's 10V output. This will make the gauges read way to high... and it can burn the gauges out over time.

The gauges (fuel and temp) are reading very high, but its very sporadic the times it does it. I went for a drive and they were fine then I pulled over and watched them rise, fall, rise again then settle back to normal. The stabilizer is still in place as the dials don't work without it (tried to cheat). I'll do a few of the checks from your pdf jobbie when I next get a chance.......either that or I'm fitting aftermaket gauges. As I can't have this problem during the summer. I'd be pulling over every 10mins for water temp check.

[taffy1967]

I will have a look at the wiper motor when I get a chance. But this whole mess started with the damn stereo. The auxilliary gauges only pull lighting power from the bottom fuse tho. As I only need light for them. Their both mechanical past that.

No need if their parking themselves properly. I was just pointing out the similarities and how something running on the same circuit can affect the gauges.

You're auxilliary gauges may only pull lighting power from the bottom fuse, but that doesn't mean there couldn't be some kind of feedback from them causing you're temperature and fuel gauges to misread.

I'd disconnect that auxilliary gauge lighting wire from the fuse box and see if the gauges work okay after a drive then.

[Big_Adam]

An Update.

This morning, drove to Hopton (10mins up the road, duel carriageway, all gauges and stereo still connected) no problems. Gauges all read correctly.

Did thing in hopton then left (about an hour in hopton) started El Gordo and the gauges flew up again......

Now they been like that for the rest of the day. Tryed twiddling the sender wires on the temp probe and fuel sender, no joy. Disconnected the stereo and the other gauges. Still no joy, gauges still reading high. but they seem to read the same valuves when they do go flying up. 3/4 tank for petrol and to the roof on the temp.

........I'm sad now.

[dklawson]

My PDF explains how the stabilizer is supposed to work by switching contacts on/off very quickly to deliver an average of 10V for the gauges. Read over that section and give some thought to what you're seeing with your gauges.

It sounds to me like your existing stabilizer is questionable... OR it's ground is intermittent. The case of the stabilizer is its earth ground connection. If you examine its case closely you'll see a little foil piece of metal pinched between the case and the circuit board. IF that connection isn't good, the workings of the stabilizer never heat up... so it passes operating voltage all the time. There could also be problems with the ground between the stabilizer case and the car's earth ground. You can run a wire under the stabilizer's mounting screw off to a remote ground point to insure a good ground. If the stabilizer looses its ground either way (bad connections between its inner foil and case or between the case and the car chassis) it will not operate and passes whatever operating voltage the car is at.

When the stabilizer passes operating voltage without regulation, you WILL see the needles drift up and down. The difference between 10V and 14V will create very high gauge readings.

If you can find the u7810 chip that I mention in my PDF, that is the easiest solution. The mounting tab for the chip is earth ground. You need to wire leads onto two of the chips leads and terminate those wires with the correct crimp terminals (leads protected with heat shrink tubing or good electrical tape). Mount the chip and connect it where the Smiths stabilizer used to be (as before... making a good ground connection). The chip can be very inexpensive and will likely fix your problem.

[Big_Adam]

On my pcb thingy on my clocks the stabilizer is connected via little metal blade connectors on screws that then connect to the pcb.

[attachment=27853:whats_What.jpg]

C**p pic but it sorta shows what I mean. But I will run a wire next chance I get to do it (tomorrow evening) to see if that fixes it. THEN if that don't work I'll go hunting for this u7810 chip jobbie.

edit

Were the in cheese am I suppose to find this chip. Maplin don't stock it so I'm already out of ideas.

Edited by Big_Adam, 21 February 2007 - 01:32 PM.

[dklawson]

I wish I could tell you where in the U.K. to source the chip. Over here it's as easy as going to www.mouser.com and giving them a credit card number for the purchase. There are a couple of different current (Amp) output versions of the chip but even a 1 Amp chip will more than cover the requirements of a Mini's instruments. For comparison, the u7810 costs under $1 (what's that today... about 0.50 GBP?). You can buy a lot of extra chips for the cost of a single Smiths stabilizer.

[Dan]

Maplin's rubbish. Try a real component supplier for grown-ups not a place to buy cheap nasty car stereo components and glowing PC parts.

Try RS Components or Farnell.

[Big_Adam]

components and glowing PC parts.

Hey the people who buy that stuff also buy the magazine that pays me.

Back to topic. It's stopped doing it again. I'm thinking ground fault now as it's so randomly intermittent. Or at least I pray for grounding fault.

[dklawson]

It sure sounds like a ground fault to me also. Obviously you're passing system voltage so it's not a problem with the other two connections. Try running a dedicated wire from the case of the stabilizer to the car's chassis and see if the problem goes away. If not, try the u7810 chip in place of the stabilizer. It could still be a problem internal to the stabilizer... like it's points temporarily welding themselves shut or being out of adjustment.