thermostat guage not working

[lectro88]

thermostat gauge not working

I bought a 2005 takeuchi tb135 that just had a engine out rebuild. I was thinking a wire left off. Called local dealer and discovered it has 2 sensors. I checked fuses and grounded the sensor wires, no change in the gauge so now I think the gauge is bad if the wire or wires are not cut from point a-b. Took the console out another real joy, its all one complete unit, no changeable parts and two massive master plugs with more wires than I care to count. Dont want to think how pricey it is. Anybody familiar with or have trouble shooting tips.

 

[r20d12]

I have never worked on one of these but, I have repaired many electrical problems on various machines. I would start by figuring out how the sensors work. You said it has two. One is probably for the warning light which would close at a certain temp and turn the light on. The other probably just changes resistence with water temperature. This one would be for the guage. The manufacture will usually give you a temperature and resistence range. Like 14 ohms @ 180 Degrees. You can let the engine warm up then, measure resistence of the sensor with a volt/ohm meter. If it is out of range you know you need a new sensor. If the sensor measures good then I would use the volt/ohm meter and some jumper wires and measure reisitence from the sensor to the temp guage. You shouldn't have more than one or two ohms resistence. if the meter doesn't change when everything is connected or, shows a high resistence then that wire needs replaced. If the resistence is high it could also mean a bad connection in one of the connectors between the guage and sensor. It may not change anything if you just ground the wires like you can on a fuel guage because you said it has a guage cluster. That could have a little computer in it that interprets the signal from the sensor and then changes the guage accordingly. I hope this was some help to you.

 

[lectro88]

Thank you r20d12 for your help.
I did not consider a chip integrated in this circuit.I remember when I unpluged one of the wires it did make the "temp idiot light" flash on/off as to indicate trouble. I was told by the local dealer the one sensor would shut the machine down if no water or high temp occured. I am going to get a manual as it is needed, on the other hand there is such an abundance of knowledge throughout this forum one could almost take common sense, present knowhow, and a friendly helping hand and fumble his way right through it. I will let you know how I progress. Thank you again.

 

[Vantage_TeS]

Correct, if you just ground the wires there will be very little resistance. Just use an ohm meter to check your baseline reading (machine not started yet but ignition on) and then fire it up and see if your number changes as the machine heats up.

However it would be worth your time checking for voltage first. If you have absolutely no change in your gauge a good way to see if the wire is cut it to find if there is any voltage on it first!

Another useful tool is the parity (usually depicted by the little ->+ sign) selection on a multimeter. Put it on this and then touch the two probes together, your multimeter should beep. This indicates a complete circut. Add a length of wire or two and you can have a helper hold one end of your circut on the sensor and you can climb in the cab and check the other end of the wiring harness with the other probem. No beep = no circut = broken wire. You just keep moving closer and closer down the harness until you find the break!

P.S. this function is VERY handy for checking fuses as alot of times the fuse has a tiny hairline crack in it but to your eye it looks good. I don't know how many hours are wasted looking for other problems when all it really was is a bad fuse. You don't even have to pull the fuse you just stick your probes on those little metal tabs on the top of the fuse. Beep = good.

 

[lectro88]

Thank you for all the pointers, I have not had time to begin a thorough check-out. Weather and work has kept me occupied.

 

[lectro88]

OK. Got it fixed.
1st off it takes a little effort 5-10 min get the console out, and today after a little closer inspection I "THINK" maybe you could replace gauges seperately and idiot lamps/bulbs as needed if required as opposed to my 1st post. Some fairly clever placement of plastic tabs and screws. 1st time I took the console apart it was a real battle, it was all metric @#$%&, saw all the wires and didn't see a way in to replace anything, late in the day and didn't want to leave it in peices, so put it all back together before it was completely dark. This is a fine example of being pushed for time and getting a mental block (your whiped attitude) I started by checking resistance changes with warm-up, all seemed good. I have to admit I thunked it was the gauge all along, knowing in the back of my mind gauges rarely give trouble, usually its anything else, Wire loose/broken wire, fuse. So after identifing wire color and no continuity in the circuit. I pulled on the wire at sensor to again verify color for all the wire loom and the wire breaks very easily 1/4" before the forked lug, hhhmmm that shouldn't happen. skin the wire and touch it to ground gauge shows life, slowly climbing to peg HOT. Yes the wire was broken internally at the engine I think from vibration and bend at termination. Crimped on a new ring lug and she works fine.Thanks again guys for your help.

 

[butchfig8]

where is the temp sender,?
what color wires?