Faulty Fuel Gauge

After recharging the battery and reconnecting it, I pressed the computer reset button as usual but instead of the fuel gauge displaying the tank contents it has defaulted to what I expect is a 'full value' of 18.7 gals??

The figure reduces as it would normally during running, but it constantly flashes. The mpg value seem OK as does the mileage.
I haven't been using the car as much lately and I assume that the gauge not reading is probably due to a bad connection somewhere? I have never had this fault before

I have been studying the wiring diagram today (1988 version) trying to fathom out the obvious connections, but after looking at it found that it was far from obvious.
I have checked the obvious things like fuses, reconnecting the battery and I also have checked the earth connections at both pillar locations, but no change.
I have removed the boot tray and checked the connector to the fuel sensor, but I could not find a 12volt live....the most I could find was .48volts on one of the leads which could possibly mean a faulty feed connection somewhere?
Does anyone know what the feed voltage should be?

I have tried switching the ignition on with the sensor plug disconnected and it showed the same 18.7 gal reading, which to me means that it is not the tank sensor??
I then tried the tester across the tank sensor contacts and it showed that there was no break in the circuit, which hopefully confirms that it is OK.

I then started to trace the wiring back to where it should pick up the live, but I am struggling to locate the main connector block locations shown within the wiring. The majority seem to be located under the dashboard console and I hope that it is a simple case of splitting and reconnecting the blocks.
Before I start disturbing the console, has anyone experienced the same problem and is there a common solution that I should try first?

I noticed in one of the strings on the forum that it could be the tank sensor control unit. I saw the box on the wing, but I didn't know what it was, are these prone to failing.....there is no mention of it in the wiring diagram.

I would appreciate any advise before I start pulling more things apart, your help is always welcome!!

Thanks

[BIG_MVS]

Hi Jeff,

I had this. It was my relay, replaced it and all was well



It's known as the "Fuel tank sender unit computer timer relay" is number "33" on the lower diag.

(Thanks to JohnC for his scanned pic )

[stephendell]

What year is your car?

The car is an '88 turbo.

If it is the relay, I assume that it is easy to check providing that you can get at it easilly, by connecting the terminals together, is it a relay in a circuit board or just wires? I am surprised though that there is a relay in the gauge wiring, as it should only be a low amperage circuit.

Is there any reason why the wiring diagram does not show either the relay or the tank sensor control box?

Thanks for responding so quickly

[stephendell]

The car is an '88 turbo

There shouldn't be a seperate control box on that one, so that eliminates that as a cause.

This is going to sound like a silly question,...... but what colour are the needles in the instrument cluster . This should give us a good idea which system is being used in your Alp.

Stephen,
When you say that there shouldn't be a control box, which box are you referring to? As I mentioned earlier, there is definitely a box attached to the front wheel arch alongside the fuel tank. I have also just looked at the Parts list and can see it listed there

I also took a look at the page in the parts list that shows all the relays, and see that there is one that has a fuel pump icon associated with it. I assume that it must be the relay referred to earlier?

John,
I think that the needle and numbers are red (which I think is the earlier type) and not the lighter orange colour of the later speedo. I am sure that that is the case but I will confirm tomorrow.

[BIG_MVS]

Dug out the part number for the relay:- 60 01 052 001. It was £19 from the stealer at the time, could be £190 now knowing renault but I'm sure you will be fine.

Thanks for that , There were 2 relays with a fuel pump icon against them, so the part number narrows it down, I will price it tomorrow.

How do you get at the relay. Is it in the group of relays above the fuse box or do you have to remove the speedo console to get at it?

Cheers

If it has got the red needles, as you say, it would be of the earlier type. From the ccts, as Stephen said, it should not have the "Tank Sender Unit", or, according to the cct, does not have a "Fuel Tank Sender Unit Computer Timer Relay" either. I would be interested to see a pic of the box you are refering to on the wing.
I have to assume that when they changed from the Red Needles to the Orange ones, the Instrument cluster for the Red Needle ones, has some form of "Tank sender Unit" built into it, or its built into the actual Tank Sensor,( the early ones being nearly £100 dearer than the later ones,) also the resistance of the earlier Tank Sensors were different to the later ones. So according to the manual the Tank Sensor goes via connectors 433 and 529 straight to the computer.
My feeling in the first place would be to break all of the connectors along the way, spray them with contact cleaner, reconnect and see what happens. I note that you are looking for 12v on the sender, but I suspect it will not be 12v, as most computer voltages are lower, and as any voltage going to the Sender is generated in the computer, I would not be unhappy at not finding 12v on it.
The manual I have is dated 1986, but it is most probably the same as yours, the early one. The pics show the location of the connectors. Hope this helps

Just a thought before you do anything else, you did not say if you did a FULL computer reset ie:- Dissconnect Battery, push and hold reset button for a good 15secs, release, reconnect battery, momentarily push reset again. That should stop it flashing, but if the fault still exists, it will start flashing again after a while. Worth a try

[stephendell]

RELAY FUEL ALP
Part number : 6001052001

Now only £15.97

[BIG_MVS]

How do you get these current price quotes Stephen, online?

Now that would be a good Members benefit

John,
Thanks for your latest replies. the extract that you sent me showing the fuel tank view is slightly different to the view that I have in my electrical diagram. Mine clearly shows to be what I suspect is the tank sensor control box (item 593), but unfortunately the key for it does not show what it is supposed to be? Your other view showing the relays is the same as what is in mine?
I have checked the parts list this morning and it definitely shows the tank sensor control box listed and it shows it being applicable across the board for the D500, D501 and the D502? The parts list also shows that there are 2 relays with the Fuel pump icon alongside them(one of them the p/no that was mentioned earlier), which are again also both listed for all the models?

This probably leaves me even more confused as to what configuration that I should have and I will not be able to tell for sure until I physically check to see if a relay exists or not.
Any idea on what is the easy way of finding the relay location? Judging by the wiring diagram location, they appear to be positioned forward of the other relays that are visibly postioned above the fuse box? I assume that this means that I will have to take the speedo console off to get at them?

Stephen,
Thanks for your update on the relay price. I checked with the stealers this morning and the P/No 6001052001 was slightly more expensive at £18.37, strangely the other relay that I mentioned P/No 7700764239 was priced at £54.17, so if one has gone I hope that it is the former? Why the difference for a relay I don't know, but it was described as the wiper relay on their listing?
What's more, if I do have to change something to get it working again I hope that it is just the relay. The price quoted for the tank sensor was £54.17 and the sensor control relay as it is described on their listing, was a whopping £171.31!!!

Thanks for all your help and keep the answers coming in. I can see a busy weekend coming on!!!

Jeff

Jeff,
Firstly, have you done the full computer reset With regard to the relay access, if I remember rightly, there are two screws holding the front edge of the Fuse Holder assembly in place, if you remove them, it will hinge down revealing the other Relays. However we have a problem identifying your fuel gauge system. As you have the boot tray removed, can you get the pt.No. of the fuel sensor. It is inscribed on the top of the unit but not too easy to see, but it is important to identify the system fitted. Also the item 593 is not in either of my manuals.... is it possible to take a pic of it, if not, how many wires has it got going to the connector, and how many spaces for pins are there on the connector, and is there a pt.No. on it
Can you tell me what parts list you have got your info from, and for what model year it refered to. Your reference to the two relays with the pump icon alongside them, does not necessarily indicate that they are for the fuel gauge, there are other relays to do with the actual fuel pump circuit, one being the "Pump Relay" the other being the "Pump Cut Off Relay" items 493 and 319 respectively in my `86 manual.
Finding the relay location rather depends on having the right manual for your model year. I have the manual for the `86, and for the `90 model years. There may be one between if someone can help with that
Let us know how you get on.
John