Thermal switch (URP1126) not playing properly

Technical MGB discussion
Ian Fozzard
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Forename: Ian
Surname: Fozzard

Re: Thermal switch (URP1126) not playing properly

Post by Ian Fozzard »

That's good Phil. It does seem close to boiling point, but in a pressurised system the BP is elevated above 100 degrees of course.
My '72 BGT has the mechanical fan driven continuously and I also have an oil cooler. Although the engine is tuned to fast road spec. the temperature gauge never goes beyond halfway. So I never have any concerns other than the engine being overcooled in some situations.
I do live in Scotland of course, not well known for it's sub-tropical climate😁.

Ian F
1972 BGT, Blaze, Navy trim, recessed grill
1961 Midget, 948cc, Clipper Blue, Blue trim and weather gear
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Charles Farran
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Surname: Farran
Location: Warwickshire

Re: Thermal switch (URP1126) not playing properly

Post by Charles Farran »

Phil,
My fan has always cut in when the Temp gauge is close to the red.(The readings on these gauges does seem to vary from car to car). These cars,including the ones with original single electric fans, have operated all over the world perfectly satisfactorily without any modification other than different thermostats. I think there is only one country , possibly the USA where second fans were installed (other than the V8 which had 2 as standard). In the past i used mine extensively in France in the height of summer with summer holiday traffic and it never gave any issues. It make sense to keep the coolant system in good order, including the radiator. Personally, i changed to 4 Life coolant (which i think is good for 10 years plus) probably some 15 + years ago & was impressed how clear it was when i drained down some 3 - 4 years ago when refurbishing everything under the bonnet. As a precaution i put new 4 Life coolant in & my neighbour put my old coolant in his Mini Moke!
It is pink, so gives the advantage of being easily seen if you have slight drip or weep somewhere.
Cheers,
Charles
1980 Roadster
Vic Butler
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Forename: Vic
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Location: North West Hampshire

Re: Thermal switch (URP1126) not playing properly

Post by Vic Butler »

Phil, you could wire a manual switch to switch the fan on manually if you're worried but I'd leave as is. The gauge probably overreads a bit anyway.
You've cured the fault so best leave alone.
1977 Stage 2 MGB GT
1975 SWB Series 3 Land Rover with a later 2.5 petrol engine
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Chrome or rubber
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Forename: Phil
Surname: King

Re: Thermal switch (URP1126) not playing properly

Post by Chrome or rubber »

Thanks Vic
I believe in leaving it alone now as all seems to work as designed, if I grow unhappy I will look at a manual addition.
Now onto the clutch and brake issues.... never a shortage of things to play with
Thanks guys, most helpful.
I am happy to be a member of such a great club and such an active register.
Phil
Vic Butler
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Re: Thermal switch (URP1126) not playing properly

Post by Vic Butler »

Phil, from experience it's best to bleed the brakes with either a pressure or vacuum system then you don't have to unscrew the brake warning light switch under the master cylinder. Mine broke but with a mirror and a small screwdriver I was lucky in managing to unscrew the broken bit without having to remove the whole unit.
The switch is activated only when the piston in the cylinder is moved and there's a leak in one of the circuits.
1977 Stage 2 MGB GT
1975 SWB Series 3 Land Rover with a later 2.5 petrol engine
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