Temperature gauge issue fixed !!

[TVRSJW]

I posted a while back about my temp gauge only starting to work once Fans kicked in then it will spring into life !

Well searching the forum and replies to my posts the suggestion was to fit fly lead from old sender connection fit resistor and then fit to the original RR sender on top on engine (that TVR never used)

Well to benefit future owners that search google like me (easier than searching this site ) to learn and find out problems and fixes hopefully this post will help someone else ?

Red male spade one end red female Bullet the other with a 180ohm resistor in between , cable only needs to be 4-6 inches

Unplug spade from sender (pair of long nose pliers can just reach down there) plug this connection into red male spade and push red female bullet into original RR temp sender !

This sender can’t have been used since new but after 23 years switched engine on and temp gauge started to rise nicely ! Stopping at 80

Thanks all for your help with this was an easy fix and took less than 1/2hr !

Now if I could have the confidence to tackle the bloody boot that does not sit flush on the drivers side !!!!!!!!

[wily_coyote]

Useful post - thanks. My gauge is ready about 15deg low, so it would be worth giving this a try.

[QBee]

I have used that method - different (RR) sender, plus a 180 ohm resistor. I actually used a variable one, but same result.
Only issue you will have is that it doesn't tell you if the car gets seriously hotter then 82 degrees, because it seems to stop at 82.

[TVRSJW]

Really ?

When I read up on it I understood that the different ohm rated resistors would set the gauge to different place on the gauge but 180ohm was a good choice but......if car got really hot it would still rise that’s what others have posted ? Can’t remember who posted in this said he took the fans out the picture and car was running hotter and with this mod the gauge raised as it should to nearly 100 then he switched it off so it should rise if there’s a temp issue ?

[Englishman]

QBee said:

I have used that method - different (RR) sender, plus a 180 ohm resistor. I actually used a variable one, but same result.
Only issue you will have is that it doesn't tell you if the car gets seriously hotter then 82 degrees, because it seems to stop at 82.

I adjusted the resistor value so the gauge roughly matched the value shown by rover gauge up to ~90C on my Griff quite a few years ago, think it was ~120 ohm in my case.

But QBee is quite correct, wired this way, the gauge will not warn you of really high temperatures/overheating. If you think about it, all you are doing is adding a fixed resistor in series with a variable resistor (the sensor) into the gauge circuit. The variable resistance decreases below 20 ohms (in my case) as the temperature rises and the fixed resistor therefore limits the current in the circuit and hence the meter reading.

[bobfather]

I used to provide link leads with a small fixed resistor and a variable pot so that the temperature could be set to be accurate at normal running temperature. I tested the original lead using kettle heated water and a spare sender connected to the dash gauge. It certainly wasn't linear but when set to be accurate at 82degC I then tested at 50 and at 97degC water as measured by an external thermometer my gauge was pretty much spot on at 97degC, a little different at 50degC

[QBee]

Mine is tuned to around 80 degrees, but never seems to go above 82-85 degrees, even when the fans cut in traffic or on a track day, and the oil temp gauge was saying 120. Suspect I need to go back to the standard sensor

[TVRSJW]

This is not what others have reported ? As I say one chap said he tested it by disconnecting the fans and the temp gauge raised as it should to warn of overheating the post is on this forum and others have reported too !

As what’s the point of a gauge that can’t earn of overheating that’s what it’s there for only reason I did this mod and what I read was it would warn of overheating ?

[Classic Chim]

QBee said:

Mine is tuned to around 80 degrees, but never seems to go above 82-85 degrees, even when the fans cut in traffic or on a track day, and the oil temp gauge was saying 120. Suspect I need to go back to the standard sensor

Can you not plug a lap top in and get the Ecu reading for temperature for a far more accurate reading and to tell what effect higher temps are having on fuelling and Ignition at the track Anthony.

I found my gauge to be surprisingly accurate when logged against Ecu sensor, it only rises above 100d after long periods stationary which is heat soak though the Ecu sensor reads a rock solid 89-90, soon as your moving a bit the gauge soon settles down so if it’s showing high on track suspect it really is getting a tad hot would be my instinct.

[Englishman]

Having selected a resistor value to ensure the gauge matched RoverGauge at 90C, when I tested higher temperatures (by disconnecting the fans temporarily) the gauge hardly moved any further. I stopped testing at 110C (RoverGauge) but the gauge was showing under 95C.

I'm still using this arrangement, but I'm aware I need to watch out for steam rather than the gauge should the engine start to overheat

[Classic Chim]

Rather than rely on gauges, over time I’ve got to know how my car performs and how the fans kick in and out. If they go off your temps should be around 90d. If they stay on for long periods your cooling system is not right or you have an over heating issue. I go by the fans as much as anything.

[QBee]

Classic Chim said:

QBee said:

Mine is tuned to around 80 degrees, but never seems to go above 82-85 degrees, even when the fans cut in traffic or on a track day, and the oil temp gauge was saying 120. Suspect I need to go back to the standard sensor

Can you not plug a lap top in and get the Ecu reading for temperature for a far more accurate reading and to tell what effect higher temps are having on fuelling and Ignition at the track Anthony.

I found my gauge to be surprisingly accurate when logged against Ecu sensor, it only rises above 100d after long periods stationary which is heat soak though the Ecu sensor reads a rock solid 89-90, soon as your moving a bit the gauge soon settles down so if it’s showing high on track suspect it really is getting a tad hot would be my instinct.

My instinct was that the water temp was not above 90 despite the oil being 115-120. Those with Spa gauges reported similar

[Sardonicus]

Oil temp wont affect water temp QBee unless using a water/oil style heat exchanger style cooler if anything the gauge is over sensitive which the LR/ resistor mod and explains the rapid movement just after cold start if anything it will indicate an over-hot condition or high temp before the engine as got there in other words its not completely in sync/linear to actual engine temps , been using the LR sender with a resistor for over 10 years no regrets

Edited by Sardonicus on Sunday 2nd June 22:39

[QBee]

Thanks Simon. I am hovering around buying a combined water/oil temp Spa gauge. That is unless there is a better way - see my musings below

Alun, the only time I really want the laptop plugged in is at 130 mph on track.......and the powers that be won't allow it.

Some time ago i mused on here about buying a Windows version of an Ipad and mounting it in the cockpit, in order to run Emerald software whilst on the move. Apart from the risk of me forgetting to look where i am going, it still seems like a good idea. A call to Emerald therefore is in order to find out where Emerald reads oil and water temps, and to work out whether their software will run on anything that recent, and whether I will be able to connect to it - the connector they recommended 18 months ago was somewhat 20th century IIRC.

That is unless anyone on here has already been down this route successfully and would be willing to share?

[spitfire4v8]

I've never looked at adding oil temp, but certainly you can control the temp gauge through the emerald ..

[Classic Chim]

QBee said:

Thanks Simon. I am hovering around buying a combined water/oil temp Spa gauge. That is unless there is a better way - see my musings below

Alun, the only time I really want the laptop plugged in is at 130 mph on track.......and the powers that be won't allow it.

Some time ago i mused on here about buying a Windows version of an Ipad and mounting it in the cockpit, in order to run Emerald software whilst on the move. Apart from the risk of me forgetting to look where i am going, it still seems like a good idea. A call to Emerald therefore is in order to find out where Emerald reads oil and water temps, and to work out whether their software will run on anything that recent, and whether I will be able to connect to it - the connector they recommended 18 months ago was somewhat 20th century IIRC.

That is unless anyone on here has already been down this route successfully and would be willing to share?

Dom once told me 115d on track is a figure you’ll see quite regularly through the friction rather than water temps rising. If you come in and fans go off within say 2/3 minutes I’d say your water is ok, if it stays on longer suspect water temps creeping up but with so much power it’s no surprise really, infact probably quite normal. 120+ is another matter though.
At my age I can’t concentrate for longer than about 15 minutes on track or mistakes creep in and that happily coincides with how hot the car is and slithering about through all the combined heat which is a bit pointless and slower. At Hethel I went out quite a bit considering I had no brakes and just preferred coming in after a few on it laps, cool down, do it again, it seemed to suit me and the car. I have chance to consider my actions then go again without a long delay and just found myself feeling fairly confident the car and I would last and actually do more track time.

Mbe do a great little 100x80mm screen you can plug in and mount ( usually within steering wheel) for allsorts of alarms and warnings you can preset, if you can do similar with Emerald it’s a really helpfull tool and probably saves thousands over time.
115/120 refers to oil temps.

Edited by Classic Chim on Monday 3rd June 09:27

[TVRSJW]

Ok so does this mod indicate on the gauge if the car overheats ? Else I don’t see the point in it ?

[Sardonicus]

TVRSJW said:

Ok so does this mod indicate on the gauge if the car overheats ? Else I don’t see the point in it ?

Of course it does otherwise it's useless and no longer a temperature gauge IMO I also have my gear/rev shift light illuminate if coolant temps reach 95 ever via my engine management , seeing as a bright light in the tacho is more likely to grab your attention than a sweeping needle

Edited by Sardonicus on Monday 3rd June 13:22

[Penelope Stopit]

TVRSJW said:

Ok so does this mod indicate on the gauge if the car overheats ? Else I don’t see the point in it ?

If your engines ECU hasn't got temperature outputs you could always fit and wire one of these to operate an in-car bleeper set to go off at a temperature of your choice

https://www.carbuildersolutions.com/uk/adjustable-...

[TVRSJW]

That’s why I was questioning the replies made by QBee and Englishman that we’re saying it would not rise with temp above the ohm resistor setting to warn of overheating ? As it’s pointless otherwise !!!!

All I want is to know if car is ever going to overheat like any other gauge would indicate