Can temp gauges under read?

[Nick P]

After changing my thermostat and otter switch, the temp still only gets to about an indicated 70'c before the fans cut in...cruising along at a steady 70mph the temp is only about an indicated 65'c where i think it should be 75-80 according to the bible....is it that my gauge is poo/under reading?
It has never ever gone above 90'c even when giving the car a workout on trackdays....??????????

[tonyrec]

These are exactly the same symptoms that plagued my Chim until the following items were changed last week.

1)New 82deg Thermostat
2)Fan Control Switch
3)Coolant Sender.

Now it performs as per the Bible.

[Nick P]

Thats what I was expecting...I presume my symptoms point towards the gauge and not something else?

[david beer]

My sender went "low" and i used the spare one on top of the head, it has a different connector and will need a resistor to calibrate but it will be much more stable as it is "deeper" in the head. I can supply details if you wish. Cost, 15p. Its just next to the water stat "bypass" that is not used with TVRs !

[shpub]

Temp gauages can read high and low depending on how the sensor itself fails. If the guauge is accuarte then you may have another problem such as a stuck open stat or even no stat at all (has been known to try and cover a heating problem).

Steve

[Nick P]

david beer said:

My sender went "low" and i used the spare one on top of the head, it has a different connector and will need a resistor to calibrate but it will be much more stable as it is "deeper" in the head. I can supply details if you wish. Cost, 15p. Its just next to the water stat "bypass" that is not used with TVRs !

I have been looking in the bible today and had come to the conclusion that my next step was the sender...I see there are TWO!!! but am under the impression that one isn't used? I would be grateful for any info you could give [e-mail] thanks Dave

>> Edited by Nick P on Sunday 26th October 20:09

[Nick P]

shpub said:

Temp gauages can read high and low depending on how the sensor itself fails. If the guauge is accuarte then you may have another problem such as a stuck open stat or even no stat at all (has been known to try and cover a heating problem). Steve

Just done the stat and otter switch

[M@H]

Nick P said:

After changing my thermostat and otter switch, the temp still only gets to about an indicated 70'c before the fans cut in...cruising along at a steady 70mph the temp is only about an indicated 65'c where i think it should be 75-80 according to the bible....is it that my gauge is poo/under reading? It has never ever gone above 90'c even when giving the car a workout on trackdays....??????????

Hi,

didn't we talk about this last week.. as I mentioned then I think, yes the guages can be out in either direction by quite an amount... BTW did you test the old stat when you took it out.?

Cheers,
Matt

[Nick P]

I tested the sender today and the resistance is TOO HIGH for the temperature which suggests to me that too much voltage is being dropped across it...therefore my gauge is under reading...so now it all adds up...new temp sender on order This may also explain why I seem to be burning an awful lot of fuel, because the ECU thinks that the car is not heated up properly and is over-fuelling all the time?

[M@H]

Glad you've got a diagnosis.. and it won't have done any harm to replace the other bits too either.

Cheers
Matt.

[Nick P]

and ive also got a spare stat and otter switch in to the bargain!!!

[IPAddis]

Nick P said:

This may also explain why I seem to be burning an awful lot of fuel, because the ECU thinks that the car is not heated up properly and is over-fuelling all the time?

ECU temp sender is seperate from the gauge temp sender IIRC.

Ian A.

[Nick P]

IPAddis said:

Nick P said: This may also explain why I seem to be burning an awful lot of fuel, because the ECU thinks that the car is not heated up properly and is over-fuelling all the time? ECU temp sender is seperate from the gauge temp sender IIRC. Ian A.

is that definitely correct? If you read in the bible is says that a lot of specialists go for the temp sender as a first stop for fuelling problems...or have I read it wrong?
Anyway, the new sender has only one connector..aaarrrggghhhh, so I'm having to grovel to David Beer for his help!!!

[shpub]

Yes it is. The ECU one has a special two pin plug. See pages 86-89 in the bible. What David is talking about is using the other sensor for the temperature guage.

If the ECU one is faulty, then get a new one.

[Nick P]

Right...I'm really confused now!!!

I took a sensor out which is near the stat and has two spade connectors...next to it is a small round one which I presumed is the spare (or 'bung')

I ordered a new sensor and whenmit turned up, it only has 1 spade connector instead of the 2 that were on the sensor I removed.......
Q1...have I removed the ECU temp sensor (in which case is the wrong one, and where is the temp gauge one because the bible shows it as near the stat)
Q2...have they sent me the correct temp sensor as it fits where the 2 spade one fits?

Sorry if I am being dumb, but the whole V8 thing is new and scarey to me

[shpub]

[
Q1...have I removed the ECU temp sensor (in which case is the wrong one, and where is the temp gauge one because the bible shows it as near the stat)

Yes you have. Page 253 on Temperature guage describes that the sensor has moved about a bit but is at the front of the engine either near a water pipe or in the pump housing. It is crowded around there. It also states that the ECU temp, the fan otter switch and the temp guage are all independent.

P 89 which shows the ECU temp sensor which is the one that you have removed. It also states that the other single spade connector is used sometimes for the temp guage.

Q2...have they sent me the correct temp sensor as it fits where the 2 spade one fits?

They have probably sent you the temp guage one which is not a replacement for the ECU one but should replace the other sensor that is connected to the temperature guage which you need to go find.
I am guessing that you asked for the temp sender for the guage and not the ECU one.


>> Edited by shpub on Tuesday 28th October 14:42

[Nick P]

mmm...Yep...
I now need to go hunting!!!...I did want to get the gauge sensor, so at least I have the correct one (hopefully)

Thanks for all the advice...I know I look like a thicky, but it's all good experience
and it's provided everyone with a chuckle at my expense

>> Edited by Nick P on Tuesday 28th October 14:50

[Nick P]

OK...I have just spent 20 mins under the bonnet and can only see (a)The 2 pin sensor near the stat housing (b)The 'spare' small round single connector next to the 2 pin sensor (c)The otter switch which I replaced last week

For the life of me, I cannot find the other one that I want to change...as mentioned above 'it is on the front of the engine', but no luck....any more clues to its whereabouts????

[david beer]

This type of stuff is good for everybody, in my opinion. The two pin on top of the head(with posh housing) is for the ECU, the single round one next to it is "the spare one" which i use. Behind the distributor is the temp sender, it is pointing forwards on a bit of old pipe about 2in long.Of course yours may be quite different.

[Nick P]

david beer said:

This type of stuff is good for everybody, in my opinion. The two pin on top of the head(with posh housing) is for the ECU, the single round one next to it is "the spare one" which i use. Behind the distributor is the temp sender, it is pointing forwards on a bit of old pipe about 2in long.Of course yours may be quite different.

Lovely...thanks David...guess who's off to the garage with a head torch on!!???...the saga continues ..........watch here for further installments