Water Temp showing High?

[TimH]

Yesterday I made two changes to the car, I replaced my wiper motor with a brand new one from SVC and replaced the top coolant hoses with Samco ones (drained the system just below the level of the top hoses).

Thankfully the new wiper motor works and now pulls the blades across the screen where my original one, and a 'used' replacement both struggled.

Unfortunately I found today that my temperatures were going through the roof according to the temperature gauge. Normally it reads a steady 90 and the fan kicks in just above that, but today it was ready nearly 140 and the fan was not kicking in either.

I thought maybe I had an airlock, but having removed the thermostat and flushed the system through and then filled again, it still reads very high and would reach these temperatures in just a few minutes of idling the engine.

I then thought maybe it is the gauge that is reading too high (possible something was disturbed as the dash had to be removed to get at the wiper motor). The wiring all looked ok, but checking the voltage on the output of the voltage regulator it reads about 12.5V without engine running and 13.5V with engine running (i.e. about 1V less that battery/alternator output).

Am I right in thinking they should always provide a steady 10V output?

The voltage regulator also feeds the fuel gauge, which now thinking about was showing a full tank - even though I must have done a fair few miles since last filling up.

So I guess I have a faulty voltage regulator? If so can I easily get one from Halfords ?

Secondly having removed the thermostat, is it strictly necessary to put it back in, or is it ok to run without one as the engines seem to warm up pretty quickly anyhow?

[dave]

Hi Tim.
It sounds like the regulator is shot.
Give Dax a call for a new one if you can't get one from Halfords.
I would keep the thermostat in as this will keep your engine at the optimum temperature whatever the gauge is reading..............Unless of course it's boiling up.
:tu

[TimH]

Thanks Dave. Just wanted someone in the know to confirm my logic (nearly gave you a call!).

The engine isn't boiling over, and although it got reasonably hot didn't seem to be 140 degress hot! (didn't want to risk it though)

I'll pop the thermostat back in, once I have a new voltage regulator and it all checks out ok.

Many Thanks,

Tim.

[SimonP]

Tim,
Your voltage regulator output is too high - but before ordering a new one, check the voltage on it's CASE relative to earth.
It could be that the earth connection to the regulator case has come adrift - without the earth connection it has nothing to "reference" it's output voltage against.

Simon.

[TimH]

Thanks for the suggestion Simon, I will check that out before getting a new one. It would certainly be more logical that a wire came adrift in removing the dashboard rather than the voltage regulator failing.

Cheers,

Tim.

[TimH]

Just a follow up, for future reference:

Earth to the regulator was sound, so this really did suggest it was faulty.

Managed to purchase a new one from Land Rover (part no 148876 - approx £10), but although this gave a lower reading on the fuel and temp gauge, the reading was a bit too low now. Being inquisitive I opened up the metal case and realised that the Land Rover part was not a solid state device (as per my original one), but rather the truly original old bi-metallic stip type that pulsed contacts open and shut equating to an average voltage of supposedly 10V (but lower than that in my case).

I didn't really want to have to wait to order a new one, so did a bit of hunting on google and came up trumps on the mg owners club site, who detail how to replace the old bi-metallic strip type with a solid state one. I whipped off to maplins and spent a total of about 50p on the bits. Unlike the article I reused the case of my faulty regulator, desoldering the old surface mount components (from which I couldn't identify the part numbers) from the little pcb and soldered on the new ones (being careful to avoid any components touching the case by using heatshrink around them). Tested it out on the voltmeter and it provided an output of 9.8V. Connected back up to the gauges and they now registered the same readings as I had been used to.

The link to the mg site is: http://www.mgcars.org.uk/electrical/...placement.html

Remember that on the pcb the terminals marked 'B' are from the battery and equate to 'Input' on the mg instructions, the terminals marked 'I' for the instruments equates to 'Output' and 'Chassis' is of course ground - which can be soldered to any where on the outer edge of the PCB as this gets grounded to the case when clamped back down.

All that needs buying from maplins is:

1 x LM317(T)
1 x 1.5k 1% resistor
1x 220 1% resistor
heatshrink to cover the regulator

Although the article says to mount the regulator to a heatsink, I didnt bother - partly because the original surface mount device didn't have one, and mainly because it then wouldnt fit in the original case. You cant use the case as the heatsink as the tab on the regulator is not an earth, it is internally connected to the output pin (2).

Just make sure you check the voltages out before connecting up to your instruments as they are not cheap to replace if damaged.

Regards,

Tim.

[SimonP]

Tim,
DIY wins again

I find that all my gauges read a little too high on the standard regulator - output is 10.04V.
Water temp shows 95, actual is 84. Oil temp shows 100, actual is 89.
Fuel shows over-full when full, just under 1/4 when empty.

Time for me to build the alternative, but I am thinking of changing the resistor values slightly so that I can "calibrate" my gauges a little.
(Thinking back, I recall Kev saying something about mechanical tweaks, but this may cure all with one electrical tweak)

Simon.