2nd Gen Non-Engine/Transmission Gauge install problems. Please Help.

[QWaller]

I have a 98 12V that has a Diprocol boost and EGT gauge. From the first install they seemed to work fine. It turns out that if left sitting for more than about an hour, the temp gauge reads the wrong value. It can start at 600 and go upward the correct amount, but the actual value is way off. It will then start cold at odd numbers, 1100, 1150, 1400, back to 800, etc. Never correct again until I unplug it and then plug it back in and it seems to reset. Vendor gave me another gauge. Did not help. Same behavior. Power supply seems ok. Thermocouple etc. Any ideas greatly appreciated.

Thanks

Quinn.

 

[Graphic man]

do you have tied into Key power?

 

[QWaller]

The gauge was installed initially by a professional at a diesel performance shop. I moved 2300 miles away 1 week after installation so have been on my own so to speak. Just checked it and it appears to have power constantly. This might be the problem? The power was run into the side of the fuse panel in the cab in a plug that has constant power. If this is the problem, where is the best spot to plug it into?

Thanks

 

[Joe G.]

Where did you check for power? Did you use a meter? If so what is the power reading? I don't know about Diprocol guages but it should work the same as other EGT gauges. The thermocouple generates different voltage depending on the temp. This voltage is very low. Any 12 voltage is used for lights and other gauge needs. Did your vendor send you a new therocouple?

 

[Joe Mc]

I agree w/Joe G. Try a new thermocouple. - MHO

 

[QWaller]

Yes I used a meter. 12. 35 volts wired in constantly. I guess next step is thermocouple if the power issue sounds ok. As I said, two different gauges, same behaivor exactly.

 

[Joe G.]

That's battery power. The thermocouple should have readings something like this list I got from Howard Durand in one of our electronics discussions. It is for a Westach:



The Westach type "K" thermocouple is the one needed for their EGT gauges.

.

Their sensor output as stated in their catalog is as follows:



Degrees F Millivolts



200 = 2. 87

400 = 7. 36

800 = 16. 58

1000 = 21. 31

1200 = 26. 03

1400 = 30. 70

1500 = 32. 90

1600 = 35. 24

1800 = 39. 67



That is the kind of voltage your gauge is reacting to. Do you have the installation instructions for your gauge? If not you could check the manufacture web site and see if they have that info on line. Westach does.



Oh yeah, forgot. Those kind of readings are at the gauge end of the thermocouple wires. The length of the special wires on the thermocouple affect the reading. My Westach installation instructions specifically say to not shorten those wires. They can be lengthened with ordinary wireing, but the special wire lengths have to be left alone.

 

[Mark Craig]

QWaller,



The guages need to be wired to key'ed on 12 volt only, most likely that's the issue!!!



Mark @ DPPI

 

[Graphic man]

i think i said that also in the 2nd post :-laf :-laf

 

[WestTN]

It sounds like you could have one of the thermocouple leads shorting to ground. I think you stated you have changed the thermocouple. If so, the replacement must have 1 yellow and 1 red lead. These things are color coded. The red lead is negative. If you have extended the wires, the junctions of both leads must be in the same temperature domain (isothermal) or error will be introduced.

 

[QWaller]

What is the easiest spot to get switched power? It does sound like the gauge does not like full time power to me?

 

[NoSeeUm]

do you have tied into Key power?

Your symptoms sound pretty close to mine initially. At first my EGT gauge just wandered all over. Turned out to be a power issue in a wiring mistake I had made. In my case it was a bad ground.



Jim

 

[Joe G.]

If there are no other 12 volt connections to the gauge the wire you are looking at is probably for the gauge light. In any case, the 12 volt connection should have no affect on how the gauge reads. It sure sounds like you have a thermocouple or thermocouple wiring problem. Do you have the installation instructions for the gauge? If not, have you checked the Diprocol web site for instructions?



Do you have a service manual? If not you should get one. The wiring diagram will show you the circuits you need.