HJ75 temperature gauge fault (2 Viewers)

[HJ75]

Hi I recently brought a 1989 HJ75 and am experiencing a temperature gauge issue.

All other gauges work perfectly but the temperature gauge reads low, I have replaced the sender and know the car is running at the right temperature, but the gauge only reads cold when it is actually at operating temperature.

Is this a typical fault that any one has had experience with?

Any help would be great, thanks.

 

[coldtaco]

I’m assuming you are talking about the water temp gauge? Usually when these act up there is a ground issue somewhere. You sure the gauge is good? I don’t know how to test them but there’s got to be a way.

 

[RHINO]

How do you know its operating at temp? Did you measure it with non contact?

I only ask because I wonder if the T Stat has been removed?

 

[HJ75]

I’m assuming you are talking about the water temp gauge? Usually when these act up there is a ground issue somewhere. You sure the gauge is good? I don’t know how to test them but there’s got to be a way.

Thanks for the reply, yes water temp. It wouldn't surprise me if there is a bad ground, trouble is finding where the gauge grounds out.

I pulled the cluster out and took an ohms reading across the two gauge terminals, was approximately 50 ohms. I've seen a few conflicting answers about what it should be, from 25-75 ohms.

It is worth noting that when I ground out the sender wire the gauge does go all the way to hot.

 

[HJ75]

How do you know its operating at temp? Did you measure it with non contact?

I only ask because I wonder if the T Stat has been removed?

Thanks for your reply, I have assumed that it is at operating temperature.

The heater blows hot air and the top radiator tank is hot to the touch.

Thermostat housing has definitely been off at some point, so the thermostat may well have been removed.

Judging by the surface temperature of the rad tank, I wouldn't want it to be running any hotter.

 

[sodafeld1]

Why not get an el cheapo ebay 12v temp gauge and plug it into the thermostat housing to take out guess work and rest assure it is the correct temp? Even could get a good led digital gauge, run fresh wires and make it permanent.

I installed two extra oil pressure gauges, electric in dash and mechanical in engine bay, very exact match. Nice, constant and reassuring feeling.

 

[sodafeld1]

Why not get an el cheapo ebay 12v temp gauge and plug it into the thermostat housing to take out guess work and rest assure it is the correct temp? Even could get a good led digital gauge, run fresh wires and make it permanent.

I installed two extra oil pressure gauges, electric in dash and mechanical in engine bay, very exact match. Nice, constant and reassuring feeling.

that 's not jack in cobargo is it?

 

[ibbi]

Hi I recently brought a 1989 HJ75 and am experiencing a temperature gauge issue.

All other gauges work perfectly but the temperature gauge reads low, I have replaced the sender and know the car is running at the right temperature, but the gauge only reads cold when it is actually at operating temperature.

Is this a typical fault that any one has had experience with?

Any help would be great, thanks.

We need to chat asap...I have the same issue on my 85 bj75!

 

[sodafeld1]

One first spanner dates with a new old car is pull all radiator hoses off, and clean, pull radiator reverse flush,(even take to radiator shop and pressure test) put a fresh thermostat (cheap part), reverse flush coolant exit/entrance on the block. reassemble and add fresh anti freeze/boil coolant. Can even run a citric acid flush going through the block recirculating to give it a good clean. Even pull the heater radiator in the dash and clean, but on the hj75 you have to pull the whole dash to get at it..
if you see rust, it needs a clean.

 

[Squash]

Just in case you need to know!
Our diesels need to be working in order for the gauge to move substantially. If you have The 1HZ there is a plug and threads available to add a real time thermo. Believe it's 5/16 " pipe thread. Follow your upper rad hose back to the engine to find the plug.

 

[ibbi]

I believe we both may have the 3b motor if I'm not mistaken... so much little work to do and difficult to disseminate the niche information. I checked my multimeter, fuses, etc but not too sure how to actually get the gauge working.

 

[AndrewHadji]

we used to test both the sensors and thermostat/gauge by getting a pot and a sous vide wand, they only go up to like 94C/ 197F ish (at least the ones ive seen) but its enough to get a good reading

Its a quick test also to see if the tstat opens at the correct temp.

I recently used this method when i replaced my gauge cluster to work out some gremlins. Better than guessing and chasing down wires if you dont have to

 

[HJ75]

One first spanner dates with a new old car is pull all radiator hoses off, and clean, pull radiator reverse flush,(even take to radiator shop and pressure test) put a fresh thermostat (cheap part), reverse flush coolant exit/entrance on the block. reassemble and add fresh anti freeze/boil coolant. Can even run a citric acid flush going through the block recirculating to give it a good clean. Even pull the heater radiator in the dash and clean, but on the hj75 you have to pull the whole dash to get at it..
if you see rust, it needs a clean.

Good thinking, I replaced the radiator and flushed the whole system as soon as I got the car, nothing looked out of place, dirty or rusty. It is worth noting that the car sat without a radiator or water in it for over 12 months.

I think it all comes down to my gauge not being calibrated correctly, it does function, just reads low.

I have since discovered more important issues to address, an inconsistent driveline vibration that I cannot seem to fix....

 

[HJ75]

Just in case you need to know!
Our diesels need to be working in order for the gauge to move substantially. If you have The 1HZ there is a plug and threads available to add a real time thermo. Believe it's 5/16 " pipe thread. Follow your upper rad hose back to the engine to find the plug.

View attachment 2780238

I was unaware that diesels need to be working to register a temp reading, thank you.

I am running a 2H engine, which I have no previous experience with.

A recent 1 hour trip down the highway saw the temp gauge needle end up at '1 quarter', being half way between the bottom at 'cold' and the middle of the gauge. I am guessing this is still wrong??

 

[HJ75]

I believe we both may have the 3b motor if I'm not mistaken... so much little work to do and difficult to disseminate the niche information. I checked my multimeter, fuses, etc but not too sure how to actually get the gauge working.

I have a 2H in my car I'm afraid, so I don't know how helpful I can be.

if you ground out your sender wire, does the gauge move?

 

[HJ75]

we used to test both the sensors and thermostat/gauge by getting a pot and a sous vide wand, they only go up to like 94C/ 197F ish (at least the ones ive seen) but its enough to get a good reading

Its a quick test also to see if the tstat opens at the correct temp.

I recently used this method when i replaced my gauge cluster to work out some gremlins. Better than guessing and chasing down wires if you dont have to

Good thinking, I will give that a try.
For the mean time I have learned to live with the gauge, fortunately it still produces a reading, just lower than what I would expect.

 

[sodafeld1]

My gauge sits like a rock once warmed up at around the 1/5 to 1/4 region from the bottom, summer or winter unless icy or snowy. Very predictable. Heater works fine. I nearly always have the heater radiator open as it gives a little bit more circulation and things are kept flowing to avoid sludge, even when warm weather, I just open the windows.. If I was unfamiliar maybe I would think it reading cold.

Use to have a neglected 40 series b engine, the temp on that went up quickly and not comforting when going up hills. New thermostat and a clean , new fluid fixed that.
I think if temp gauge doesn't shoot all over the place you are ok, definitely below half way. I imagine the electronics of temp gauge to be fairly simple things. Not sure how much is a new one, if not exy worth getting a shiny.

 

[HJ75]

My gauge sits like a rock once warmed up at around the 1/5 to 1/4 region from the bottom, summer or winter unless icy or snowy. Very predictable. Heater works fine. I nearly always have the heater radiator open as it gives a little bit more circulation and things are kept flowing to avoid sludge, even when warm weather, I just open the windows.. If I was unfamiliar maybe I would think it reading cold.

Use to have a neglected 40 series b engine, the temp on that went up quickly and not comforting when going up hills. New thermostat and a clean , new fluid fixed that.
I think if temp gauge doesn't shoot all over the place you are ok, definitely below half way. I imagine the electronics of temp gauge to be fairly simple things. Not sure how much is a new one, if not exy worth getting a shiny.

Thank you, that is very valuable information.

Mine sits about 1/5-1/4 when on the highway (lower when driving around town), similar to what you mentioned. That may just be how it is, and I needed to learn where it likes to sit.

One day I need to replace my weeping water pump on the 2H and might as well give it a new thermostat.
Until then I think I am safe now that I have gotten used to it.

There is a local speedometer repairer, Ringwood speedos. I might take it out and see what they think.

Thanks again,

 

[sodafeld1]

I would get onto the leak. I like things tight n clean. Ends up cheaper on fluids too. Oz summer over 40c, 2-3hrs from civilization, you don't want a leak. Cooling is one of the first places to start love.

 

[HJ75]

I would get onto the leak. I like things tight n clean. Ends up cheaper on fluids too. Oz summer over 40c, 2-3hrs from civilization, you don't want a leak. Cooling is one of the first places to start love.

Very good point, I'll order that replacement pump.
Will be interesting to see how it handles the upcoming summer...