JD 4600 temperature goes in the red within a minute or so running from cold.

[zaschf]

Hello all,

I have a really weird temperature behaviour on my JD 4600.

Some time ago it started to go in the red within minutes from cold start but, as the engine warmed up it was coming back to a 'normal' temperature reading.
Now it goes in the red within minutes from a cold start and stays in the red even though the engine is not even luke warm.
I've replaced the sender which made no difference.

While testing I noticed in the first minute of running that when I turn off the engine but leaving the ignition on, I get a substantial different reading.

Any ideas would be much appreciated.

Cheers,
Frits.

 

[mrmikey]

just a shot in the dark here never having worked on a JD, how is your voltage reading, could the regulator be going bad? I remember some of the older cars used to have a regulator to run the dash gauges, when that went south all the gauges acted funky.....Mike

 

[zaschf]

Thanks for your suggestion, Mike.

The fuel gauge doesn't have any problems....

A bloke next door from use came up with the idea of a bad engine earth strap. A couple of mVolt could already upset the temperature reading.
The temp sensor is a single wire one.

Cheers,
Frits.

 

[mfreund]

You should be able to test the Guage by disconnecting the wire and reading the guage. Then ground the wire and read the guage. One should be full hot and the other full cold. If that works, it is the sender.

 

[DLTTrekkers]

Good advice

 

[zaschf]

Thanks for that, mfreund.

I've already replaced the sender and it did not solve the problem.
What I can't work out is that with the engine just luke warm, like in the first 30 seconds from cranking, the gauge climbs steadily to well past overheating.
I measured the resistance of the sender within a minute of cranking and it still reads over a 1000ohm which it should be when cold.
At 80DegC it's reading around 250ohm which is correct for the stock sender.

I hope it's not the gauge because that means a whole console replacement.
But then, it sometimes comes right after 10, 20, 25 minutes (it's a bit of hit and miss when it comes right) but most of the time it stays in the red.

 

[doxford jim]

What about installing an aftermarket temperature gauge. The sender can be swapped out and the gauge can be added to the consul. Shouldn't be hard to do and probably pretty cheap as well. Just a thought, maybe a gas filled sensor bulb type might be better then you won't get any electrical problems.

 

[zaschf]

Thanks for that, Jim.
I see what you're saying but it's an integrated console which will be pretty difficult to disassemble without causing problems with the other electronics.
I've already had a go at it with the electrical diagrams available to me.
And bolting a temp gauge on top of the console would look really stupid.

 

[Zebrafive]

The wire from the sensor to gauge might have a short to ground, giving the hot reading.

 

[mrmikey]

Any chance you could have a water blockage or an air pocket where the sending unit is, a screwed up thermostat maybe....Mike