Temp sender compatibility

[Pete Lewis]

there is a old posting about me and Commer 

i dont need wikipedia 

 

[cliff.b]

2 hours ago, Chris A said:

Mine does the same, and stays there for what seems like a lot of distance, by the time the tank is getting to the low mark it is more or less correct. I do keep saying I must check it out but never do because it does warn me in time that I need petrol.

I presume it's the sender/float in the fuel tank but as I've just brimmed it I can't investigate.

[Chris A]

1 hour ago, cliff.b said:

I presume it's the sender/float in the fuel tank but as I've just brimmed it I can't investigate.

I tend towards the theory of the float blocking somehow and not rising to maximum. I have fished about a bit but without any effect so will live with it unless I run out other bits to fiddle with🤔

[cliff.b]

1 hour ago, Chris A said:

I tend towards the theory of the float blocking somehow and not rising to maximum. I have fished about a bit but without any effect so will live with it unless I run out other bits to fiddle with🤔

That's never going to happen, is it lol

 

[Chris A]

1 hour ago, cliff.b said:

That's never going to happen, is it lol

 

You might say that but I couldn't possibly comment 😏

[Pete Lewis]

you know if its going to happen its dark  raining and you re in your best shirt 

Pete

[Peter Truman]

My Sprint ran out of fuel but was still indicating half full thought it was ultra efficient the float some how got stuck not a drop in the tank Iwas doing 110kph on a freeway no indication of a problem it instantantly ran out.

easy to check as float goes thro the top of tank why it stuck I never determined just replaced float and double checked it was free when refitted.

[Chris A]

1 hour ago, Pete Lewis said:

you know if its going to happen its dark  raining and you re in your best shirt 

Pete

I'm safe then, I don't have a best shirt

[SkillyHerald]

My Herald 13/60 runs permanently 'hot' at the 3/4 mark on a Smiths gauge adopted from a MkIV Spitfire.

I've tried a new GTR108 sender and it made no difference.

What does make a difference - nearly a whole 1/4 division - is turning on the fan on the heater (swapped from original to a SMART car) 

Makes the inside toasty but removes any worries about overheating - very welcoming when stuck in the queue to get into last weekend's Newark autojumble.

[johny]

I would look into this further as it sounds like the engine could actually be running hot. What thermostat have you got fitted and is it opening fully? Also whats the voltage supplying the temperature gauge (although if this was wrong it would also affect the fuel gauge accuracy)?

What state is your radiator in, perhaps you could use an infrared thermometer to measure temperatures? 

[Pete Lewis]

using the heater will obviously take heat out of the system but does it do it without the fan as opening the heater flow changes the bypass 

and it may well have a blocked pipe , the one under the manifold   the adaptor into the water pump can get restricted with crud 

time to check the thermostat  should be an 82C  make sure it has a jiggle pin in its rim to air air bleed out.

do check the voltage stabiliser common point in funny readings you need a steady /pulsed   10.5 volts ( depends if its orig or electronic)

the fact the gauge came from a spitty is of no consequence

Pete

 

 

[Colin Lindsay]

15 hours ago, SkillyHerald said:

My Herald 13/60 runs permanently 'hot' at the 3/4 mark on a Smiths gauge adopted from a MkIV Spitfire.

What does make a difference - nearly a whole 1/4 division - is turning on the fan on the heater (swapped from original to a SMART car) 

So if you turn the heater on, the gauge drops from 'hot' to half way or thereabouts?

[cliff.b]

I have now received my GTR108 temp sender & the resistance is significantly higher than the GTR106 that I was previously sent as suitable for Spitfire, Heralds etc.

At ambient temperature it was as about 480 ohms compared to 350. At approx 85C it was 40 ohms compared to 110. 

[cliff.b]

I contacted the supplier regarding this and have just received the following response.

"Thank you for bringing this to our attention. It seems that this item is for a spitfire between 62-68, so very early spitfires. Most likely changed to GTR108 for the MK3 onwards. We have adjusted the listing to try and avoid this issue in the future"

[Pete Lewis]

thats a rough assumption  as early are moving iron not stabilised ....bit of a wild idea for a dealer who should know better

Pete

[cliff.b]

1 hour ago, Pete Lewis said:

thats a rough assumption  as early are moving iron not stabilised ....bit of a wild idea for a dealer who should know better

Pete

If the early cars were non stabilised then surely a lower resistance sender would result in an even higher reading? 

Or am I missing something 🤔

[johny]

yes, the old moving coil meters used a different technology from the later bimetalic strip type and the current they need to operate is quite different so components arent interchangeable.....

[Pete Lewis]

they are "moving Iron " workings  they have two opposing coils acting on a magnetic armature so voltage variations when driving does not alter the reading

the stabilised have a bi metal strip which is heated by a coil of wire around it hence as the voltage varies the coil heat follows and readings change 

these get a stabiliser  to feed a constant voltage otherwise you would get low readings at idle and higher readings at revs  as the battery voltage works from 12.5 to 14.5 volts when driving 

 so moving iron needles will wag about on bumps and rough roads  and flick up to read immediately

stabilised move slowly and needles stay steady

why  ....Cost 

Pete

[SkillyHerald]

On 14/06/2021 at 08:13, Pete Lewis said:

using the heater will obviously take heat out of the system but does it do it without the fan as opening the heater flow changes the bypass 

and it may well have a blocked pipe , the one under the manifold   the adaptor into the water pump can get restricted with crud 

time to check the thermostat  should be an 82C  make sure it has a jiggle pin in its rim to air air bleed out.

do check the voltage stabiliser common point in funny readings you need a steady /pulsed   10.5 volts ( depends if its orig or electronic)

the fact the gauge came from a spitty is of no consequence

Pete

 

 

Thanks for the ideas.

Running with the heater open or closed doesn't seem to make much of a difference until I turn the fan on.

I'll check the manifold pipe and the type of thermostat.

I know the stabiliser is giving out 10V, it is one of the eBay solid state ones

On 14/06/2021 at 11:53, Colin Lindsay said:

So if you turn the heater on, the gauge drops from 'hot' to half way or thereabouts?

No, unless I turn on the fan, which is a blowing monster compared to the original.

[Pete Lewis]

then if theres nothing wrong check the rad temp with a cheap stick thermometer from the chemist (or better) 

if the engines not over temp you can always  .....bend the needle    if its paranoia setting in  

its an indicator of whats going on  your looking for adverse changes , but most dont see the gauge or a warning light until  you see steam or get a lot of knocking  

my Citroen Cactus 130 has speed and fuel only   you get used to minimal and no worry gauges 

Pete

[Colin Lindsay]

1 hour ago, SkillyHerald said:

No, unless I turn on the fan, which is a blowing monster compared to the original.

That's what I meant, sorry if it wasn't clear but I meant the blower.

I was just wondering if this is more electrical than temperature-related, along the lines of a voltmeter where the needle drops when more electrical units are switched on. 

 

[cliff.b]

Just to update my original post, after fitting the correct sender I let the engine come up to operating temp with the rad cap off & a thermometer inserted.

I could see a slight flow of coolant into the top of the rad from about 75C & then a rush of it just over 80C as the thermostat opened. At this point the temp gauge was now  reading a little below normal.

Replaced the cap and went for a drive, adjusting the electric fan to cut in as soon as the gauge registered above normal. With a bit of fine tuning the fan mostly only comes on when the road speed is below 30 mph and cuts out soon after speed increases again. The electric fan sensor is in the bottom hose and after getting my adjustment right while driving, it was set dead on 85C.

it was like this for my entire 125 mile journey over mixed roads yesterday and the temp gauge only moved a fraction either side of normal, so I believe all is ok 👍

[Pete Lewis]

so you measure engine temp at the top of the head but control the fan from the cold end of the radiator   that doesnt make sense to me 

the is shutting the door after the horse has gone

pete

[Clive]

17 minutes ago, Pete Lewis said:

so you measure engine temp at the top of the head but control the fan from the cold end of the radiator   that doesnt make sense to me 

the is shutting the door after the horse has gone

pete

There is a reliable temp gradient between top and bottom of the rad, so fan can be controlled from either. 85 in the bottom hose sounds correct to me, I think the difference is 7degrees from memory when I did mine. 

[cliff.b]

38 minutes ago, Pete Lewis said:

so you measure engine temp at the top of the head but control the fan from the cold end of the radiator   that doesnt make sense to me 

the is shutting the door after the horse has gone

pete

Hi Pete. My thinking was coolant temperature at the top hose is a function of the heat of the water going in at the bottom + the heat generated by the engine. So if the temp of the water leaving the rad is ok there is no point cooling it further with a fan. If the engine output goes up or the forward motion isn't sufficient to cool then the water leaving the rad might get too hot which will make the engine hotter still so the fan will cut in to maintain a constant returning water temp and hopefully control engine temp.

It seems to work so far but if I find it doesn't do the job adequately I will change it.  🤔