TR4/4A TR4A Is it really running that hot!?!

[boeingpilot]

I need to appeal to those wiser than myself - that is to say pretty much everyone on these forums!

My TR4A seems to be running hot, about 3/4 up the scale in top gear cruising on the highway. Around town it climbs about 80 to 90% up the scale. Though it has never pegged on the red, if I continued to operate it I'm afraid it would. It will, however, idle happily on a 100 degree day all day long with out the electric fan ever having to come on.

Here's the catch. While driving, the aux electric fan doesn't come on all the time. I set it to come on at 180F, and I'm running a 160F thermostat. The fan is also designed to operate for 1 minute upon shutdown which it does every time I turn the car off.

I flushed and refilled the radiator, and replaced the thermostat, and the brakes are not binding.

I've heard these temp gauges can be inaccurate. Is there an easy way to tell if it's simply an instrumentation problem? Voltage stabilizer? Bueller?, Bueller?

 

[PeterK]

The temp gauge and the fuel gauge share the voltage stabilizer. Is your fuel gauge accurate?

ISTR voltage stabilizer output is 10VDC. You can test with a volt meter.

 

[boeingpilot]

Actually, no it is not. Thanx much. I'll swap voltage stabs and see what happens.

 

[mrv8q]

Try taking it's temperature with an infrared thermometer......

 

[TR3driver]

BTW, the output from the original voltage "stabilizer" is NEVER 10 volts (unless your battery is dying and just happens to be putting out 10 volts).

The stabilizer output actually switches between full battery voltage and zero; such that the long-term average is 10 volts.

Easy way to check the stabilizer is to look for that voltage swing. With the key on, pull the lead off of the temperature sender, and connect a test light from the lead to a good ground. If you can see the light flash on and off, the stabilizer is most likely OK.

The stabilizer also relies on the speedometer case being grounded, so it might not be a bad stabilizer even if it's not working.

 

[Geo Hahn]

I 2nd the idea to get an independent opinion using an infrared thermometer or such. Apart from the gauge and voltage stabilzer another suspect is the sender. Sometimes these get replaced with an incorrect unit -- many will fit but the wrong one may give an inaccurate reading.

 

[Adrio]

I agree about the issues associated with measuring the output of the voltage regulator. I think if you have an old analog meter you might be able to "see" the output depending on the time constant of the meter.

As far as the sender goes, I have charaterized one of those and have posted the results on here in the past (I am at work - don't tell anyone - so I don't have access to the table I generated). What you will find if you search on my old posts, is a table of temperture vs. resistance, of the sender unit.

 

[TR3driver]

I think if you have an old analog meter you might be able to "see" the output depending on the time constant of the meter.

The "flash" is very slow (about like a turn signal), so can be seen even on a slow digital meter.

About the only thing that wouldn't show the varying output would be a "hot wire" movement like the dash gauges use.

 

[Geo Hahn]

...As far as the sender goes, I have charaterized one of those and have posted the results on here in the past...

Interesting table, it's here:

https://www.britishcarforum.com/bcforum/u...enso#Post203308

 

[MGTF1250Dave]

Aloha,

My experience with an electric temperature gauge is that if your voltage stabilizer fails, at road speed you will observe high temperature readings and at idle the temperature gauge will drop rapidly to a below normal indication. This is most likely due to dynamo output being a higher voltage at road speed. As Geo points out, an infrared thermometer is a good tool for your tool box and not that expensive. Harbor Freight frequently offers them for about $35.

 

[boeingpilot]

Aloha,

My experience with an electric temperature gauge is that if your voltage stabilizer fails, at road speed you will observe high temperature readings and at idle the temperature gauge will drop rapidly to a below normal indication. This is most likely due to dynamo output being a higher voltage at road speed. As Geo points out, an infrared thermometer is a good tool for your tool box and not that expensive. Harbor Freight frequently offers them for about $35.

That is exactly what is happening. As I said it will idle away all day long with no problem, but as soon I hit the highway the needle goes to about 80%. I just ordered a new voltage stabilizer from Victoria British. Now, where the heck is it located on the car!?!

 

[MGTF1250Dave]

I can't say for certain since I don't have a TR4 but I expect it is located in the engine compartment near the fuse box. I'm sure someone will let you know for certain. The voltage stabilizers I've seen are about 1 inch wide and 1.5-2 inches long, metalic base and a circuit board material top and as I recall four connections for push on electrical connections.

 

[TR3driver]

Now, where the heck is it located on the car!?!

On the back of the speedo (which is why I suggested to check that the speedo case is grounded before replacing the stabilizer).

 

[Adrio]

On my TR4A (again I am at work and can't confirm)my memory says it is located up under the dash at the junction of the fire wall and right side "wall" In other words (my car is left hand drive) above the right foot of the passenger in the area of the glove box.

It has been several years so I can't give any warranty to my memory.

 

[Tinster]

Now, where the heck is it located on the car!?!

On the back of the speedo (which is why I suggested to check that the speedo case is grounded before replacing the stabilizer).

<span style="color: #000099">Randall-
When my stabilizer failed, I moved it's location from the speedo case
to a more reasonable spot in the passenger footwell. I installed
a seperate ground for the new stabilizer. Everything works just fine.



d </span>

 

[TR3driver]

Seems reasonable, Dale, if that's what suits you.

But mine wasn't broke, so I didn't fix it. The passenger footwell on a Stag is already packed with relays and wires and circuit breakers anyway, and I don't especially enjoy laying on the back of my neck to get at them!

 

[4aKen]

My TR4a from new read about three quarter up the dial and stop/go/wait hot day commute would look directly into the gates of heck. (Can't write heck?..seems a bit much.)

 

[Geo Hahn]

On the back of the speedo...

On my TR4A... above the right foot of the passenger in the area of the glove box...

Possibly the change pint did not correspond with the 4A introduction as Adrio's description would be correct foe a TR4.

 

[TR3driver]

On the back of the speedo (which is why I suggested to check that the speedo case is grounded before replacing the stabilizer).

My bad. I thought it moved to the speedo with the introduction of the 4A, but apparently it wasn't until later. Likely started with the TR5/250.

Sorry!

 

[boeingpilot]

Thanx for all the info. Turned out to be the voltage stablizer. I put a new one in and all is well in my world...