This has been driving me crackers for ages. Ever since I've had the car, the temp guage has read low, not getting above the 1/4 position on the temp guage. The radiator gets hot, there's no leaks anywhere and it doesn't use or loose any water, Radiator cap has 13 marked on it (presumably PSI). If you run the engine with the radiator cap off, it's possible to see a sudden gush of water as the thermostat opens and also feel a sudden change of water temperature. The thermostat is new. The car gets up to normal running temperature quickly and the heater pumps out lots of hot air (better than the modern VW, in fact)

I had the same problem on the TR6, so took the quick and easy route of changing the sender, only to find out it ws the voltage regulator.

The 2000 also has a new voltage regulator (semiconducter type and checked for correct voltage with a professional DVM). I've swapped over the sendor with others that I have and these make no difference (the only thing I have not done is take the one out of the TR to test, just in case my stash of spare senders are all duff).

I've tested the guage by remvong the wire at the sender and confirming that when open circuit, the meter doesn't move off the Cold setting and when shorted to the engine block, it does go up to the top of the hot section and rests agains the end stop.

The one and only time that the car has overheated (failed jubilee clip on bottom hose; hose came off the rad and I left a nice trail of steaming coolant behind me), the temp guage accurately moved to the "hot" position.

I've tested or changed all the obvious things - what have I missed?

Kevin

Which thermostat have you got in... there are several different ones. 74, 78, 82, 86, 88

74 would make it sit at a quarter.

88 should sit it at half

I **thought** it was an 88. I'm pretty sure that was what I ordered from Mr Rimmer when I replaced the previous one. And I think I orderded it by part number, not description.

But that would explain it, wouldn't it?

The old thermostat appeared to be stuck in the open position - it was covered in scale when I removed it. I didn't actually expect to find one fitted because of the problem.

Kevin

Hi Kevin,

The thermostats usually have the temperature marked on them. Usually. Under all the crud on an old one of course.

That might explain the low temperature gauge, but not the effective heater?

Cheers,
Mike.

Check your engine earths. My temperature gauge seemed particularly erratic when I had a bad earth between the battery and turret, particularly when I had the headlights on. I think everything was earthing through the thermostat sender cable.

Once I'd fixed that, it always read 1/4 but would creep up at high speed or in summer traffic jams.

I fitted a new thermostat and it stayed rock steady at 1/2. Recently it's back to 1/4 again. It's either the cold weather or a duff thermostat.

Hi Kevin,

My guess would also be an incorrect or defective thermostat, but the engine earth strap is definitely worth a check. A third possibility might be a high resistance condition somewhere in the wiring between temperature gauge and sender (i.e. enough to depress readings within the usual range but not sufficient to prevent the gauge going to 'hot' under the two conditions you have described). Are the connections on the back of the gauge itself clean and tight?

Regards,

The thermostat should be stamped "82", i.e. 'start to open' at 82C. An "88" is too high (which is probably why the No.1 supplier, CW, doesn't list it). An "88" may be OK for the current very cold weather but you'd be well advised to fit an "82" for the rest of the year - if indeed your present one is an "88".

Compared with an "82", an "88" would, if anything, give a slightly higher reading on the gauge as the engine warms up because the coolant would get hotter before it opened.

The gauge on my Triumph never reaches the mid position even though the operating temperature appears to be about right, and I've heard of this with several other Triumphs as well. I'd guessed that the sender was ready for renewing but will be interested to learn of the experiences of others.

It'd be worth checking the running temperature of your engine with some type of thermometer. Those non contact ones are great, especially for testing the operating temperature of bearings and stuff........

Driving my car today, the heater output felt a bit weedy which tends to suggest that my newish thermostat isn't working correctly or that the rest of the cooling system is just too damn efficient in cold weather!

I've checked the actual temperature with the mark 1 back of the hand - and also by listening to the car cooling down after a run of 20 miles or so. The water filled components are too hot to hold for more than an instant and there's no sound of boiling, so I'm happy it's not overheating and its definately up to about normal operating temperature judged not very scientifically by the output from the heater. I should check the earths next time I get a chance, although there's no problem with any of the other electrical stuff.

It's a horrible coincidence that I had exactly the same problem with the TR and that in the end did turn out to be the sender. Maybe I should swap the senders between bot cars to see if the fault follows the sender. Either that or I should stop being a perfectionist!!

Kevin

The 1500 ran straight to hot when we got it. Swapped the sender and it ran just under 1/2. Then checked the stat, which opened too early, so fitted a new one. It then always ran at about 1/4, until I got fed up with that in September. Bought another stat - marked 88degrees. Took out the one in there to find it was an 82degree one. With the latest new stat fitted it runs on 1/2 - just like I think it should!