Hino temp gauge problem

But that would show up as starving the starter for juice wouldn't it (doesn't have its own earth)? Besides, I only just replaced this - it ripped a front engine mount and managed to rip the earth strap off, next time someone went to start it the starter took its earth through the PS line which got very hot very quick and blew a hole in it. So I know that earth is good.

While playing with it yesterday I ran a jumper lead from the battery earth to a clean spot on the body - no help. The lights also make it play up. Just with me starting from cold I had to leave it on high ilde for a good 20mins, then with fan and all lights the needle would shoot up over 2/3, switch them off and it drops like you've switched the ignition off. But also so does returning to idle... I measured the the voltage at the two +ve in terminals behind the dash and get battery voltage - 28v or so with no lights or fan, 26v when they're on (this is when it plays up). I then ran a hot straight from the battery to these terminals and no change. When I let the high idle off it drops to 25v and the gauge returns to normal. WTF?

I've been looking for fuse 19 - there is no reference to finding it. I got them to send me the fuse diagram, and it confirms 19 is for the instrument cluster but no closer to finding it in the fusebox itself...

I didn't realise that this was an electronic engine, if this is the case, check the terminals in the multi-pin plug / socket connecting the cpu, as this (as i have found anyway) is the biggest cause of heartache and frustration. The plugs tend to wear or open up the terminals over time due to vibration and such, causing bad connections. Sometimes the plug and cable are not fixed down properly, which makes the problem worse. Hope this helps.
Cheers
Alistair

Bitsa wrote: I didn't realise that this was an electronic engine, if this is the case, check the terminals in the multi-pin plug / socket connecting the cpu, as this (as i have found anyway) is the biggest cause of heartache and frustration. The plugs tend to wear or open up the terminals over time due to vibration and such, causing bad connections. Sometimes the plug and cable are not fixed down properly, which makes the problem worse. Hope this helps.
Cheers
Alistair

Well the fuel pump has a massive electronic unit hanging off the back of it so I guess that makes it an electronic engine... Not CRD though. What do you mean by The CUP? There are units all over the place, how do I find the main one? I've pulled out and cleaned the ones in the dash that many times

The CPU is the main computer to monitor and control the engine, (CPU = Central Processing Unit), sometimes called the ECM,(Engime Contril Module)
There is normally a main unit with looms heading out to all the ancillary units or sensors, to send signals back to the CPU or engine control module. i think these units themselves are fairly robust, just the connection going to / coming from them can and do sometimes give trouble. If the wiring going to the plugs has a bit of length to and is not secured properly, (not allowing much , if any movement), the wiring shakes the plugs about and opens up the terminals enough to cause a bad connection or a complete disconnection. Bad connections can and in some cases do , cause the terminals to heat up enough to melt the plug or start a fire, if enough current is involved.
I would just unplug any you find and make sure that is clean and a good connection.
Hope this helps
Cheers
Alistair

wedgetail84 wrote: But that would show up as starving the starter for juice wouldn't it (doesn't have its own earth)? Besides, I only just replaced this - it ripped a front engine mount and managed to rip the earth strap off, next time someone went to start it the starter took its earth through the PS line which got very hot very quick and blew a hole in it. So I know that earth is good.

A starter motor can draw hundreds of amps, an air con clutch a few amps and the temperature sensor would draw milliamps, so it wont take much of a crook earth to send things awry. I would be tempted to run a jumper wire direct to the sensor body from the negative battery post and see what happens. Then try running a jumper wire from the CPU to the sensor terminal. To access the wire in the CPU plug, unfold a paper clip and solder it to the jumper wire. Then you can push the paperclip between the sensor wire and its seal in the plug to wire everything up with the plugs still connected.

According to the wiring diagram, there is an ECU as well as the CPU, but I think the CPU is sending the temperature information to the ECU, as well as displaying the information on the instrument cluster.