Erratic temperature reading !

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derodster

derodster

Member
Posts
17
Location
Co.Kildare, Ireland
Well maybe it's not erratic, but I am mystified as to why the gauge is nearly in the red when i turn the ignition on.
I have checked the earth from the battery and it's well earthed. There doesn't seem to be any problem on the wiring to the gauges ie the clock is running fine and it uses the same earth connection... whatever could be causing this I wonder...
 
sender faulty or the wiring to it chafed and earthing.
try removing the wire off it and shorting to earth, should read max then
 
As above - sender is kaput is the usual suspect IME - but the wiring, as already mentioned, can get fubarred anorl... test as above :)

IMO, a capillary gauge is a good replacement and upgrade, preferably Durite. :)
 
Thank you for the replies,
Indeed I did suspect the sender and wiring, so today I replaced the sender (Steve Parker one) and replaced a good length of the cable. The old one was a rather haphazzard affair done by someone previously just added apiece with twisted connection. I added fresh cable and soldered/crimped connectors.
I also replaced the thermostat.
So, I turn on ignition and needle stays put, then fire her up and wait a few minutes, needle starts rising and rising , into the red zone (if it was red once back in 1985)
Full scale more or less. I did add a resistor that I had used on previous sender, it dropped the needle a little but still up there !!!
What's on my mind is the obvious matter is the sender correct for the 1985 gauge on the dash or is it posssible the water pump isn't working.
How to check it withoout removal,
I did wonder if I took the small top pipe off while running would or should it be pumpimg water out

All guidance and ideas welcome as I would love to get her back on the road
 
derodster said:
Thank you for the replies,
Indeed I did suspect the sender and wiring, so today I replaced the sender (Steve Parker one) and replaced a good length of the cable. The old one was a rather haphazzard affair done by someone previously just added apiece with twisted connection. I added fresh cable and soldered/crimped connectors.
I also replaced the thermostat.
So, I turn on ignition and needle stays put, then fire her up and wait a few minutes, needle starts rising and rising , into the red zone (if it was red once back in 1985)
Full scale more or less. I did add a resistor that I had used on previous sender, it dropped the needle a little but still up there !!!
What's on my mind is the obvious matter is the sender correct for the 1985 gauge on the dash or is it posssible the water pump isn't working.
How to check it withoout removal,
I did wonder if I took the small top pipe off while running would or should it be pumpimg water out

All guidance and ideas welcome as I would love to get her back on the road
Click to expand...
What engine have you got in? Original or conversion? I doubt very much if it’s reaching max temperature within a few minutes, LR diesels take ages to get up to temperature. Sounds like a sender/gauge mismatch.
 
Yes, it's a 1993 ex Disco 200tdi
It was fine up to a couple of weeks ago, then wasn't move ontil a couple of days ago and this happened
It always had a high reading on the temperature gauge so i had inserted a 120ohm resistor is series and that worked fine.
Then recently i decided the Steve Parker sender might work so I tried it but unfortunately not.
But what is really puzzling me is the high reading, theres no prob with the wiring that i can see. battery is well earthed to engine and chassis
I had a look benind the instruments and all looks ok there too
Very puzzling
 
derodster said:
Yes, it's a 1993 ex Disco 200tdi
It was fine up to a couple of weeks ago, then wasn't move ontil a couple of days ago and this happened
It always had a high reading on the temperature gauge so i had inserted a 120ohm resistor is series and that worked fine.
Then recently i decided the Steve Parker sender might work so I tried it but unfortunately not.
But what is really puzzling me is the high reading, theres no prob with the wiring that i can see. battery is well earthed to engine and chassis
I had a look benind the instruments and all looks ok there too
Very puzzling
Click to expand...
I have a Disco 200 in my ‘87. I’ve never got around to fixing the mismatched sender and gauge and I just got used to reading it abnormally! Recently though the gauge has crept up to max, even though outside temperatures have been cold. I checked the wiring and noticed a break in the insulation in the engine bay, I fixed this and this has cured the maxing-out, although it still reads high. I really need to fit a ‘proper’ gauge and sender that accurately reads an actual temperature.
 
Last edited:
I have to ask.:confused: Why are folk so dedicated to trying to make old landy temperature gauges work ? Finnicky and inaccurate at the best and when donkeys years old worse than useless.:eek:
Fit a new after market gauge, TIM or Durite and know what your engine temp is in numbers degrees,:) I did so a long time ago and looking at the gauge as it comes up to running temp I can tell when the stat opens.
 
Rhis mornings update
So i turned the switch, i didnt start her, just turned on ignition and noted zero temperature. Then i left her on for an hour and when i checked back still zero.
So i guess i can discount temperature sender as the problem.
So now I'm deffo thinking its a pump problem, why or how is a mystery but I'll get on it later...
 
Until the thermostat opens that will be the case.
If you are concerned that coolant is not circulating and the temp gauge is not reliable get a IR [ infra red ]
hand held temp reader. You can then point it at head, thermostat housing, rad top and bottom, hoses and even the heater and find the problem.
 
derodster said:
Well maybe it's not erratic, but I am mystified as to why the gauge is nearly in the red when i turn the ignition on.
I have checked the earth from the battery and it's well earthed. There doesn't seem to be any problem on the wiring to the gauges ie the clock is running fine and it uses the same earth connection... whatever could be causing this I wonder...
Click to expand...

No earth on the guage (other than the lamp) .... live in, live out (to the sensor) and this provides the earth. The hotter it gets the lower the resistance and the more voltage passes/the higher the guage reads (an NTC Thermistor).
A resistor in circuit will allow the engine to get hotter and/or the guage move less.
 
Disco1BFG said:
IMO, a capillary gauge is a good replacement and upgrade, preferably Durite.
Click to expand...

tottot said:
Fit a new after market gauge, TIM or Durite and know what your engine temp is
Click to expand...

OP:- there's a theme here... :) IMO, the easy way to KNOW what the temp actually is, is to fit a proper gauge - Durite IME ( have no experience of TIM ) .... Gauge and sender mismatches on re-engined deafeners are pretty much the norm, so, ......;)
 
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