20 replies to this topic

[77_LX_HATCH]

I've done a lot of searches on here, and have gathered that they regulate at 10V - is this correct?

Where can I get a new voltage reg for the back of the SLR dashes, and does anyone have the part number?

I work in electronics, so could easily solder one in, just need to know if it is actually supposed to regulate at 10V. Would prefer a genuine item though.

The one on mine is cooked, will not regulate at all, and as a result, it heated up the metal element, melted through the plastic stop for the needle on the gauge when it was full, and is now sitting at full scale (haven't pulled it fully apart yet).

Have had the sender out, it reads fine. Tested the new sender without the car running, so the voltage would've been at around 12V or so. The gauge seemed to read fine. Took it for a quick run, filled up the tank, and it went right to full scale and past :( :( Im assuming when the alternator is charging, its putting out over 14V, which in turn caused the fuel gauge to read massively high, and (expecting the worse) fry the metallic strip in the gauge.

If this has happened, is there a fix? Can you get these strips newly installed by a instrument technician?

If not, I think Dangerous stated that temp, oil pressure and fuel are all the same. Is there any issue with me using the temp gauge, as a fuel gauge once i've fixed the issue?

I don't use oil or temp gauges, as I have external ones fitted, and dont want to really spend the whole 300 bucks buying a new cluster which i cant guarantee in the first place anyway!

I know these are common questions, and I have used the search functions, just after some clarification!

Cheers

Mike

[77_LX_HATCH]

Ok Just rang my local gauge guy.

He seems to think they are 5V reg's. Does this sound right to anyone?

If so I could whack a 7805 in there.

Cheers

Mike

[77_LX_HATCH]

I might pull the old one apart and have a look how it works (its stuffed anyway!!).

The new ones just regulate in the form of heat, so shouldn't be too much of an issue. If it drops more voltage (from say 14 to 5, it will dissipate more heat than dropping from 10 to 5v, etc). I will see how it goes and let you know. Cheers!

Mike

[76lxhatch]

5V. A small packaged item from Dick Smith will do the job but they are very slow to get the needles up to begin with. I've used these before when no other options, just screw it to the metal dash and heat isn't a problem.

I believe some (if not all) of the factory regulators are designed to give a short higher voltage initial whack to the gauges to get them to rise more quickly when you first turn the key

[77_LX_HATCH]

No worries then guys!

Im not too concerned about initial start up of the needles, all i really need is an indication, as im sick of running out of fuel!

Cheers

Mike

[fuzzypumper]

5V. A small packaged item from Dick Smith will do the job but they are very slow to get the needles up to begin with. I've used these before when no other options, just screw it to the metal dash and heat isn't a problem.

I believe some (if not all) of the factory regulators are designed to give a short higher voltage initial whack to the gauges to get them to rise more quickly when you first turn the key

Yes, the old mechanical reg had its good points, like mentioned above by the inherent way they worked.
Yes its 5volt , they are marked 50/5/1 = 50 % duty cylcle , 5 volts, 1 hertz.

When the 3 gauges are at full load the current draw is about 700ma, now this is under the 7805's max operating current of 1amp but these regs arent efficient, My bench testing showed the 7805 was running at 55 degrees only after 15mins of use with a small heatsink. Also the initial delay of the needles to get into position and give you a correct reading(like the mechanical reg) at startup was about 30-60sec.
A larger heatsink still wasnt any better. I also used a current series pass tranny 2n2955 to tackle the current draw away from the 7805 and a but still the heat generated at room temp was still too high.( Can you imagine a 30 to 40deg day)? I also tried LM317 or 340 but even these got very hot too.
Incidentally the 7805+TIP2955 combo with heatsink in a 80x50x30mm jiffy box is exactly what Ringwood Speedos will sell you as a replacement for $50.
They also have a really small 5-7volt adjustable DC-DC module than sells for $100. Its really efficient , requires no heatsink(deos not get warm) and can fit inside the dash cluster. Yes alot of money.

However I had sourced one of these http://pdf.directind...-27879-_22.html



But this one, http://pdf.directind...-27879-_30.html
,one of he 5volt HERA 5s would be probably would work just as well(its smaller than the Athena 5)

Edited by fuzzypumper, 29 June 2009 - 11:04 PM.

[76lxhatch]

I agree the 7805 is far from ideal, but strangely they do seem to last despite the temp (also in the full sized Holdens there is a big alloy structure in the dash which makes a good heat sink). They are extremely cheap too.

Does the flash one you bought operate the gauges any better? $100 is expensive but perhaps not heaps in the scheme of things if it works well.

[fuzzypumper]

I never bought the $100 one from Ringwood speedos.
The Athena 5 module from Powerbox in pictures is one sourced from my brothers work(free old stock ). Yes it works great. Being a DC to DC module, it generates no heat. The trim pot is there to fine tune output voltage. I actually set mine to 5.1V as this emulated the old regs readings exactly. However seeing these gauges arent acurate it probably doesnt matter.
The only thing with the Athena 5 being an industrial device is its awkward size. I couldnt find a reasonbly small jiffy box with mounting tabs to ploink it in. They were all to big to accomodate which then severly compromised many of the possible mounting positions.

If I didnt have extra VDO gauges in my dash between the cigarette lighter and the cluster I could have just siliconed or hot glued the Athena5
to side on the cluster and insulated the pins, but i have limited room there. I suppose I could insulate the pins with blobs of silicone and just cable tie it to the wiring loom on the back of the dash cluster.

Other modules in the range that I reckon would also work, but I havent tested are listed below, Price $$$, sorry I coulndt tell you:

Apollo 8 MAF 08 009 5v, 2000ma, 10W, DIP size 20x32x14mm, Non adjustable ( advantage-really small size, 94% efficent input current only 647ma )
Hera 4 MAD 24 003 5v, 2000ma, 10W, 24 pin DIP size 51x25mm, Non adjustable ( advantage-still small siized, 82% efficent input current 1660ma)
Athena 3 MAE 13 006 5v, 3000ma, 15W, large size 51x51mm, Non adjustable ( advantage-higher power output 15W)
Athena 5 MAE 15 006 5v, 3000ma, 15W, large size 51x51mm, Adjustable ( advantage-Higher power output, adjustable by adding trim pot)
Athena 6 MAH 16 006 5v, 5000ma, 25W, large size 51x51mm, Adjustable ( advantage-Even Higher power output, adjustable by adding trim pot)

[77_LX_HATCH]

Wow that is a bit pricey.

At work we have "big" 7805's, cant remember the package size but they handle up to 5A. Might just put one of these in, even though the 7805 would be sufficient, as i'm only running one gauge not all 3.

Will let you guys know the progress when I get around to pulling the dash out over the weekend!

Hopefully will get some happy snaps of the gauage i think I have broken :(

Cheers

Mike

[77_LX_HATCH]

Update:

Put a 7805 in and tested my temp and fuel guages with a known working sender unit.

At 5V, all the gauages read too low (about half way at full). Im not sure about the quality of my gauges either, as they have never really read correctly.

To compensate, i bought a couple of 6, 8 and 9 volt regualtors. 9 volt was too high, and would read over full when actually full. Didnt get to test the 8, as i cooked it accidentally. At the moment the gauage is still reading a bit low, with the 6 volt regulator in it. In the future I will make a adjustable regualtor with a LM317, and vary the voltage to get the correct readings on the gauges.

I think my gauges could be out of calibration, hence why they aren't reading correctly with the usual 5 volt regulator.

Cheers

Mike

[77_LX_HATCH]

No worries mate, there are lots of tech articles on here where I got most of my info from! Just sharing some experiences if anyone has had the same sort of issues.

There is a sticky which lets you identify what is wrong with the gauges, use that first and then work out if its a regulator issue. If it is I would never pay 80 bucks for a gauge place to change the reg. Personally I have no problem with the slower start up from the 7805, but some may not like it as it isn't "factory".

This is the simple circuit you can make to obtain the perfect output voltage for your gauages. As fuzzy said its about 5.1V or so, so this could easily be obtained. The capacitors in the circuit are not really needed either!

http://www.national....f/LM/LM317.html

After you have the perfect reading from your gauge you can just glue the pot, so it should never change.

Cheers

Mike

[Rockoz]

You can up your voltage level in 0.6V increments easily by chucking a diode in the ground leg of the 7805.
Each diode in series should up the voltage for you. Any cheap one will do.

[77_LX_HATCH]

Top Idea Rockoz!

[Rockoz]

Will have to use a seperate heatsink isolated from the chassis though.

[fuzzypumper]

Update:

Put a 7805 in and tested my temp and fuel guages with a known working sender unit.

At 5V, all the gauages read too low (about half way at full). Im not sure about the quality of my gauges either, as they have never really read correctly.

To compensate, i bought a couple of 6, 8 and 9 volt regualtors. 9 volt was too high, and would read over full when actually full. Didnt get to test the 8, as i cooked it accidentally. At the moment the gauage is still reading a bit low, with the 6 volt regulator in it. In the future I will make a adjustable regualtor with a LM317, and vary the voltage to get the correct readings on the gauges.

I think my gauges could be out of calibration, hence why they aren't reading correctly with the usual 5 volt regulator.

Cheers

Mike

How do you figure that? What do you call a working sender unit and how are controlling the sender?

If you hook up the 7805 and put a 10ohm 1watt resistor in place of the sender, the gauge should go the full line.
A 31ohm load resistor should send the gauge to 1/2 , but usually these arent accurate so dont be surprised if it only shows anywhere
between 1/4 to 1/2. This normal, however if cant get the gauge to move past the zero line with 31 ohm load, then i would say
you have problem.

Edited by fuzzypumper, 07 July 2009 - 12:02 AM.

[77_LX_HATCH]

The sender I used is an actual fuel sender which measures 10 ohms to about 70 ohms. Just using a regulated 12 v supply, then put the reg in.

Basically with a working sender, it doesn't get more accurate. I can swing it either empty, full, half way to give me an actual reading.

I have put the gauges in the car again and I'm getting a good linear response from the gauge with the 6V reg, but I will have to wait until I fill up and see what my reading is.

On the bench with the 6V regulator in and gauge set to full, the gauge read about 3/4 full.

Cheers

Mike

[fuzzypumper]

Ok, if both gauges read exactly the same i.e 3/4 when they should be reading full and running on a 6volt reg, then I speculate they must have been cooking for while on the old faulty reg and probably have a limited life especially if you gonna raise the voltage any higher to compensate.
Also look the back of the cluster and the gauges brass nuts, washers and lugs for tarnished brass and corrosion on the connectors.
That was the cause eratic readings initially on one of my clusters.

[76lxhatch]

I speculate they must have been cooking for while on the old faulty reg and probably have a limited life especially if you gonna raise the voltage any higher to compensate.

I would be a little suspicious of this too

[77_LX_HATCH]

Yes I agree with both of you on that.

In it's past life I think they have been cooked at some stage, and then the regulator replaced, as the gauges always read lower than they were supposed to.

I understand me limiting the life of the gauges with the 6 volt reg, so I may even change back to the 5. The other reg cooked and I was just sick of running out of fuel!!!

Im just after some sort of a reading...you get used to, "if the gauge reads a quarter, I really have about half a tank" so that suits me

I have a mech and other elec temp gauage and oil pressure mounted in my console so I dont use the others anyway.

Cheers for all the help and interest guys!