Petrol Gauge Electrics

[Guest Neo84]

Hey up all....this is my first post as a full member of Rhocar!!!

 

I have ditched the old dash on my RH and am in the process of fitting a brushed aluminium plate. I have bought a voltmeter, tacho, petrol gauge and am planning to have a gps speedo/mp3 - if I can figure out how to program the old PDA i'm using for the front end.

 

Only problem I have is the Petrol gauge - When the tank is full it shows full...but when empty it still shows 3/4 full. I assumed (wrongly) that adjusting the resistance in series with the gauge I could adapt the range!!

 

Does anyone know how to get this to work?

 

All the best,

 

Graeme

[Guest Neo84]

17 views and no reply?? Is this a bad sign??

[Guest chris brown]

adjusting the resistance in series with the gauge I could adapt the range!!

Correct it wont! You need a sender of the correct resistance for your gauge otherwise you will not get the full reading but there again most of us using the sierra sender and gauges in a smaller tank do not have full movement on the gauge. Fitting a resister in series with the gauge may give you a correct reading at one end of the gauge but will defiantly be wrong at the other end where it is looking for 0 ohm's

[Longboarder]

You will get closer with a resistance in parallel with the gauge. Need to find out what resistance the gauge needs to read full and empty and what resistance the sender gives on full and empty and then do the sums. Probably easier to bend the float arm!

 

Nigel

[Snapperpaul]

Try and set it so it shows empty correctly as a stop gap until you can sort it out properly, we all know when it is full, it's when its getting low we really need to know.

If you use a GPS speedo ( i have one on my PDA with Tom Tom) it will not pass SVA as they check speed on the rollers

[Guest Neo84]

Thanks for this...I will try to wire it up in parallel today. You are of course right that I only need the empty end of the scale.....only problem is that the dial hardly moves from full to empty. I may just have to buy the sender unit too.....bugger!!

 

The car has been registered since 1997 and therefore does not need to go through the SVA?? Does it? So my GPS Speedo should be ok....although...I am still going to wire up the original in the car for the purpose of mileage tracking (MOT etc)

 

I just can't stand the all in one speedo units.

 

To be honest, I bought the car when it was a bit of a mess...and have spent quite a lot of money doing it up....only other option is to buy a new set of sierra gauges as the others are knackered.

 

The electrics are also in a bad way and I am currently wading my way through masses of wires...replacing the split or broken insulation.

 

Nightmare!!

 

And don't get me started on the trimming!!

 

Many thanks for your help though...it is very much appreciated...Bit new to all this!!

 

Graeme

[Snapperpaul]

If its all registered your OK so no SVA (lucky you). sierra guages get them from the scrappy, dead cheap. if you bought the fuel guage new, email the company with your problem ( tell them as much as you can about the sender) they may have a solution

[Guest Neo84]

Thanks....I will do that!! Have not tried the resistor in parallel yet though. I borrowed a resistor box today which allows you to hook it up then just turn one of the 6 dials until you get the required resistance. Saves having to work it out!!

 

I finished the new Dash today....it looks sweet!! I have also just developed my own car alarm system for the exmo - detects movement when the car is invaded.

 

So much to do....and so little time to do it.

 

The GPS speedo works a treat....I set the PDA into the dash so it is always there - charging from the car battery while it is running.

 

I'd quite like to put a piccy on here but don't know how yet!!

 

Cheers,

 

Graeme

[Snapperpaul]

Pics need to be very small Jpeg with lots of compression and under 50Kb if you send me one ill size it for you. Ther is a sizing program on this site that you can have a go at. Use the test area to have a play.

[Guest Neo84]

kewl ok I'll have a go - I should be able to resize in photoshop - Watch this space!!

[Peter Bell]

Hi Graeme, good luck with the resistor box, I tried it once without much success. My gauge shows full with a full tank and half full when it is empty, the best I could come up with was empty when empty and indicating half full when full!

Peter.

[Guest Neo84]

Thanks....If I come up with a solution then I will let you know!! I teach electronics so I am in the midst of creating a variable circuit that will allow a user to adjust a sender to any gauge. If I manage it and it works I'll send you a board!!

 

Plan to have a crack at it next weekend!!

 

G

[Guest craig030774]

take the sierra sender out of the tank and with a bit of careful soldering short the inbuilt resistor at the top of the printed circuit board

 

this does work i have done it

[Guest salty_monk]

Can also host pics on www.photobucket.com & then post the code into here, just copy & paste, works very well...

[Guest timswait]

I dismantled the Sierra instrument binnacle and took out the workings for the petrol gauge to put in a nice looking (but non-functioning) housing I had. The problem was it then read backwards! (ie full when empty and empty when full). I then took the water temperature gauge workings from another binnacle, since that works in the opposite direction. Then I needed to fit resistors in series and parallel to make it read correctly, which it does now. I used small preset variable resistors, meaning to replace them with fixed ones when I get round to it, that was a couple of years ago......

One thing: Be careful when you adjust the parallel resistance. If you go too low then you're effectively putting a short across the gauge. If the sender is also at the low resistance (I think full) end of it's travel then that will put quite a hefty current through it. And hefty currents in the petrol tank aren't to be recomended!