How Hot Is It In There

[Guest Flea]

Hello People

 

Well I am doing, as many of you have, putting Capri clocks in my 2b.

 

However I am having trouble getting the gauges to work, the Speedo and rev counter work fine along with the oil/batt/main beam and indicator. Just can’t seem to get the petrol gauge working or the temp gauge.

 

I know that a lot of the wires are like for like on the Capri wiring loom and on the sierra, however the ones I think are different are the petrol and temp gauge.

 

Is this correct? If so which wires go were? I no it’s not hard to work out but I am just checking I have done it right! If the wiring is correct then were do I look for the problem?

 

Also I have replaced the fuel pump and sender unit (external type pump) (this is the sohc EFI engine) with the internal type pump and sender of the DOHC engine. Do you think this has anything to do with the problems with the petrol gauge?

 

Look forward to your replies

[Mitch]

Hi Flea

Check the link for wire colours on NW web site.

As for the Temp, Have you fitted a white sender in the block or are you still using the sierra one.Sender must match gauge.

Petrol gauge is more difficult. I have Capri clocks and my fuel gauge reads incorrect, 3/4 when full, and empty at 1/4 full.

try earthing the wire to make sure the gauges work first.

HTH

Mitch

[Big Jim]

The fuel gauge is all to do with the resistance of the sender at the various positions, relative to the clock. If you want to get it right, then you will need to match the resistance of the sender , to match the requirements of the gauge at full and empty, to do this, I think that you would need to alter the small resister that is built into the sender unit.

Alternatively, by bending the float arm wire, you can get the gauge to read correct at either FULL, or at EMPTY, but it won't be right anywhere else.

I've had to do this with mine, when it reads empty, it is empty, but it only starts to read on the gauge (3/4 full) when the tank is actually 1/2 full, so I know that when it says 1/4 tank, fill up now! less than that, PANIC!!!!

[Guest Flea]

This white temp sender in the block, is this from the Capri? And would I not get any reading with the wrong sender?

 

As for changing the resister I think I will pass! I like the idea of bending arm so I no when I need to full up and using the guestimate gauge for 1/2 3/4 and full, I mean do we really need to know if we have a full tank or half, I think not just as long as we no when to full up.

 

There are no implications on the SVA if your petrol gauge is incorrect?

[Big Jim]

There are no implications on the SVA if your petrol gauge is incorrect?

 

 

Yes there are, you have to go with a full tank of petrol, so you need the gauge to read full, You can do that by earthing the fuel gauge wire.

 

Ford make about 12 different temp senders, from experience, the lads who have fitted the Capri clocks have found out that this is the correct sender for those clocks.

Any sender must match the gauge / clock that it's attached to, not the engine or car.

[Mitch]

the white sender is from various years but was used on all Capris. (around £9 from ford)Mine didnt read at all. Earth the wire with ign on and watch the gauge, it should go to the top. if so change the sender.

As for petrol you will know when its empty.. It stops.

at the sva again earth the wire on the tank sender so it reads full just dont tell him you.ve done it.

HTH

Mitch

Jim Beat me to it

[Guest Ant]

A couple of comments on the "earth the fuel sender wire" idea.

 

Firstly, at my first SVA the fuel gauge was reading less than 1/4. I told him it wasn't working but that I'd filled up at the garage just down the road and he said "that's fine". A fuel gauge isn't a requirement - Ron Champion in the Locost book recommends saving dosh by having a dip-stick which you put through the filler neck after a few hundred miles to see how low your fuel is.

 

Secondly, when you earth the wire at the sender you're sticking far too much current through the gauge and voltage regulator. This is fine to test the gauge and the circuit, but I wouldn't leave it connected like this for more than a few minutes at most. The gauge will get hot and may burn out, and the voltage regulator could do the same.

 

Anyhow, don't worry about it for MOT or SVA - if the tank is full you'll be fine.

 

Ant

[Big Jim]

I accept that so long as you can prove that the tank is full you should be OK, but the sender is just a resistance to earth, mine will not show full movement unless it is earthed, the resistance at full gauge is minimal at full movement, but it won't go past 3/4.

[Guest Bernie]

If checking the gauges with their sensor input first shorted to an earth to give high scale and then open giving low scale doesn't result in needle movement then possibly the voltage regulator is either shot or not correctly wired in. Check the positive supply to both instruments, the regulator is normally only used on the temperature and fuel gauges.

[Guest Mike Gouldsborough]

Can I add my two-pennyworth on the problem with fuel-gauge and tank sender relationship? My Exmo is fitted with a Smiths Classic gauge and Sierra sender unit. With the sender out of the tank (so that is the absolute zero petrol condition) and wired up I can adjust the two adjusters on the back of the gauge, and move the gauge needle on its spindle, so that I get zero on the gauge. Great! That is the most important thing as far as I am concerned.

 

I have tried loads of experiments with bending the sender arm into allsorts of shapes. With the sender out of the tank, and the arm in its highest position, the best I can manage is three-quarters full on the gauge. I could live with this. Putting the sender back in the tank, and the best the gauge will register is barely half, quickly going down to less than a quarter after using probably only a gallon or two of the expensive stuff!

 

Anyone got any ideas on how to improve the range shown on the gauge?

 

Regards

Mike G

[Guest Ant]

I too have a classic smiths fuel gauge and a Sierra Ghia sender unit. I have added a 66 Ohm resistor in parallel to the gauge and it now reads full when the tank is full, and empty when the tank is empty. Trouble is it's not linear in between. The gauge drops very quickly at first, and slows later. The ideal situation is the opposite of this, hence getting the most accuracy when the tank nears empty. Mine is good enough for me, and the trip on the speedo is used to confirm what the gauge reads.

 

I worked out the 66 Ohm requirement by measuring the sender resistances at various positions, measuring the gauge resistance, and modelling the circuit in a spreadsheet. I then played with 3 possible resistors - one in parallel to the gauge (hence reducing gauge current), one in parallel to the sender (reducing sender resistance and increasing gauge current), and one in series with the gauge and sender, reducing the current of the whole lot. For my set-up I only need one of these resistors to get something I'm happy with.

 

I have midified the arm on the sender, but my aim here was to maintain the full range of the sender in my tank. Reducing this range is an alternative approach, but I imagine it involving a lot of experimentation with liquid in a tank. I'm happier with numbers on a spreadsheet, but I'm sad like that

 

Interesting that you've adjusted a smiths gauge. Where is this adjustment? Do I have it on my gauge and have overlooked it?

 

Ant