30 replies to this topic

[Mike92]

Model: Austin Mini Mayfair
Year: 1989
Description of problem (please be as in depth as possible):

Ever since I've had this Mini (about 3 months now) the petrol and temperature gauge have never really worked properly. The temperature gauge has never worked, and the petrol gauge is different everyday! At first when we got the car, and the tank was full it would only say 3/4 full, and now, with a new petrol sender unit and a full tank, the gauge only says just under half way is full.

As I have said the petrol tank has a new sender unit so that is probably not the problem, possibly some sort of electrics problem? Does anyone have a idea what the problem could be? Me and my Dad are not the best at electrics but we'll give it a try!

Thanks, Mike.

[dklawson]

Let's start with a brief introduction to the gauge system before discussing what could be wrong.

The gauges do not operate at full charging system voltage. For Minis built after 1964 there is a device called a voltage stabilizer that drops the gauge operating voltage to an "average" 10V. This reduced, controlled voltage is supposed to isolate the gauges from the changing voltage levels normally present on the car and thus allow the gauges to have more consistent readings. If you have both electric temperature and fuel gauges, they are both supplied from this common voltage stabilizer. Smiths gauge clusters mount a replaceable stabilizer on the back. Later Nippon Seiki gauges handle this a little differently. Not knowing much about the NS gauges I won't post any information here as I might get it "wrong".

In your case, you have a semi-working fuel gauge therefore there must be some output from the stabilizer. However, you said the temp gauge isn't working. This implies that the temp sending unit or the wires to/from it could be bad. This could include any flex circuit connections on the back of the gauge cluster. Start in the engine bay. The temperature sending unit will be near the radiator end of the engine, on the cylinder head. Look for a green/blue wire that should be connected to it. Remove this wire from the sending unit (assuming it is connected). With the ignition switch in the "run" position, earth the metal connector on the end of the green/blue wire. The temperature gauge should slowly go to full. If it does go to full, this indicates you have a bad temperature sending unit. If the gauge stays on cold, you either have a break in the temperature gauge wiring or a problem with the gauge itself.

After you try this, post back with your findings.

[Mike92]

Cheers Doug - good info.

Did as you suggested. Earthed the temp sender wire with ignition on and, yes, gauge went to 'hot'. So, next step is to source and fit a new temp sender unit. - Problem solved????

Have similar problems with the fuel gauge - earthed it and it went to full, but when connected as per standard only registers 1/4 full (with full tank). So, I guess voltage regulator needs replacing - need to find where it is located yet!! I guess it is behind the instrument binnacle somewhere??

Thanks,
Mike

[carthy79]

Hey Mike,

I believe that the voltage stabiliser mentioned above is not that easy to change on the Smiths gauges, and that's where guys like this are handy;

http://www.speedycab...com/repair.html

There are a few helpful posts around here, if you do a search.

Carthy79

[taffy1967]

Although being a 1989 Mini Mayfair probably means there'll be no replaceable voltage stabiliser, because it'll have the Nippon Seiki type gauges and the stabilising is done within the gauges themselves.

Anyway the fact the fuel gauge reads full when the sender spade connector wires on the side of the tank are shorted probably means the fault is with the actual sender unit inside the fuel tank. I believe bending the float wire helps get a more accurate reading?

[Irishmayfair]

Try the smiths voltage stabiliser located behind the guages....
Mine was doing the very same thing and i tried everything else too and nothing did any good until i replaced the stabiliser.... Perfect!

Its just a small Relay type thing, About the size of 1 square of Yorkie (The chocolate bar)
silver in colour withe 3 pins on it

Hope this helps!

[dklawson]

If this car does have the Nippon Seiki gauges, I encourage you to read over the following thread related to the NS gauges.
http://www.theminifo...p;#entry1682458
This thread was started in late December by Stormintrooper. He was looking at the issue of the voltage stabilizer on the NS gauges. Dan and I had some suggestions for him to try... I was hoping by now he would have reported back with his findings. Perhaps I'll send him a PM to see if he can update us.

EDIT: Sorry. I meant to add that yes, if shorting out the temperature sender's green/blue wire made the temperature gauge go to hot (and it was not reading anything prior to this test) then I certainly would install a new sending unit. However, if there is a problem with the voltage stabilizer also (as hinted at by the fuel gauge behavior) then your new temperature sending unit will only address half the problem. You are likely to have a working gauge again but it will likely have the same untrustworthy behavior as the fuel gauge.

[Mike92]

Just to say that yes this car does have the NS gauges (Nippon Seiki Gauges).

Will update when we fit a new temperture sender and had a look where the voltage stabaliser is and open the dashboard.

Thanks,
Mike

[dklawson]

Taffy is familiar with the NS gauges where I am not. Hopefully he will continue to post advice on this for you. In the meantime, do check out Stormintrooper's thread that I posted a link to earlier.

I PMed Stormintrooper. Unfortunately at this time he does not have an update on his work with the NS gauges.

[Mike92]

Right another little update, the car did have a new head gasket so we replaced the temperature sender with the old one and the gauge moved very slightly, so I presume that yes it is the voltage stabiliser that is the problem, it's going to be fun taking out the dashboard!

How ever this does have the Nippon Seiki gauges so will I need to get a new gauge system or is it replaceable?

Thanks

Edited by PoweRMikE, 19 January 2010 - 01:58 PM.

[Big_Adam]

Mine went nutty once, turned out I just screwed the PCB plastic thing on the back of the gauges. Might be worth a look.

[Mike92]

Alright, took the car to a garage (Filham Moor Garage) which specifies in Mini's (saw a white, pretty standard Mini with a South Devon Mini Club sticker on the front windscreen), so we asked him if he can do it and he was pretty certain what was the problem and how to fix it, so we booked in it for next week.

Thanks everyone for the replies!

[dklawson]

When you are happy with their repairs, please remember to post to this thread what was done to fix the problem so others can benefit from what you learn. Thanks!

[stormintrooper]

provided im not out getting down my xmas lights off the house (yes i know its rather late) im going to pick up a chip and do as said in my topic tomorrow, all i have to do is put some insulating tape between the stabiliser contact points, solder wire to the chip...add ring terminals and simply screw the rings using the existing screws and then mount the chip somewhere, if not to the bulkhead to the cluster and il simply buy a heatsink that fits the chip

[taffy1967]

Right another little update, the car did have a new head gasket so we replaced the temperature sender with the old one and the gauge moved very slightly, so I presume that yes it is the voltage stabiliser that is the problem, it's going to be fun taking out the dashboard!

How ever this does have the Nippon Seiki gauges so will I need to get a new gauge system or is it replaceable?

Thanks

Surely if the gauge moved slightly after fitting a dfferent temperature sender, then it's the temperature sender that is to blame and not the actual gauges?

Again please let us know how you get on, because my temperature gauge hasn't worked in years. Even though I have the occasional dream that it starts working again, only to wake and then feel disappointed.