EGT does not work, replaced all!!
 

I had one EGT gauge that did not work when I bought the boat. I relaced the sensor (Gaffrig), replaced the gauge-Gaffrig double indicator), now replaced the wiring.... I have replaced everything and it still does not work. The gauge is proven good. It was originally installed by Arizona Speed.........Any ideas?????

Did you try starting the engine:o :o :D :D Sorry couldn't resist:rolleyes:
Seriously though , you replaced the gauge,thermocouple and wiring. do you need 12v to the guage?
I know the thermocoupler produces a miniscule amount of voltage to operate the guage but dont know if you still need a 12v source.

:eek: Cute....really cute!!:D The gauge requires 12v only for the lights, not used for the gauge needles.....I am mystified!!!:confused:

did you try connecting the bad guage to the good circuit? The one that works. If it does operate, is there a spot by the thermocouple where the wire is spliced. I mean a plug or something. You could put the gauge there and see if you get a response. You know substitute untill you find the broken link in the chain.
Thermocouples use a specific type of wire for each type of thermocouple, "k", "j" types. And the wire is polerized. You cant just hook up the leads, they are color coded for a reason.. If you have volt meter, and there is a connector by the engine, you can check for a voltage at that point, then start the motor and see if it increases!!

Hope this helps, good luck.

Dick

Mr Gadgets,.... I did all that replacement & substitution thing. swapped sides of the gauge & it works..... I cannot however check for thermocouple voltages because they only use milli-volts ofr less. A multimeter is not sensitive enough to read them.
All parts are Gaffrig & new. Wiring polarity was observed. Continuity is good but still no reading. The thermocouple leads are fairly short and the gauge/coupler indicate from 600- 1600 degrees. Pretty warm to be sticking your arms into!!:D

If the sensor is mounted in the manifold at the #2 cylinder, if that cylinder was "dead", would the sensor not read at all??? I would suspect that at WOT, even with a dead cylinder (NOT that it is) it would indicate SOME heat....but nothing!!! Over $200.00 and no fix yet. :(

thermocouple output
 

You said the output of the thermocouple was too little to be read by your meter. I think it is also too little volts to drive their gage without 12 volts to work their signal conditioning. Try emailing their tech department to check wiring and to find out how they suggest to diagnose the proublems. The tech help email is [email protected]

some of the cheaper EGT's use the DC milivolts supplied by the thermocouple. The problem with these is a needle that is not steady. The higher $ units use 12V DC to power the meter. The EGT for my diesel truck is this type.

I would not call $128.00 for a Gaffrig gauge cheap, and Gaffrig sensor was $48.00 and the Gaffrig wire (25 feet) was another $50.00. There instruction sheet says specifically that 12v applied to the meter will cause severe damage. Besides, it is a dual gauge, reading EGT for two engines & one works fine and is steady as a rock. When the engine leads are switched at the gauge, it reads fine on the other side!! :eek: I would say that if these are "cheap" parts, then Gaffrig needs to lower the price or everyone here better quit depending on them for other function monitoring as well. Please re-read the thread & it is said that the gauge works on one engine and not the other & all components were replaced.
I was sure that someone here had experienced a similar problem before and could offer some advise.:confused:

Blown forumula,

"swapped sides of the gauge & it works..... "
You put the good gauge on the bad circuit and it worked?? Did you put the bad gauge on the good circuit, did it work?

I have a sheet somewhere that gives the voltage reading at a certain temp for "K" type thermocouples. I know it is in millivolts, but a good quality digital meter should give you an indication. I am looking at the idea of looking at the circuit in place that is not working. To check the wiring from the gauge back. If you use the good gauge as a volt meter to check the wiring of the bad circuit, does it work? If you swap the wiring from one gauge to the next does the problem switch? If there isnt a way to check the thermocouple in the engine bay, connect the gauge or volt meter directly to the thermocoupl, then you will could remove the thermocouple and put it in the other engine.
I use a Fluke meter with two inputs to check my temps. I also have used a volt meter, but I dont remmber what values I saw on the meter. But I have removed the thermocouple and applied heat from a propane torch to excite the thermocouple to check to see if I get any output from it.
If you subed everything, then the problem should have moved at one point, if you have a bad component. If you have a dead cylinder, it would read room temp or ambient temp. You wont see that with your gafrig gauge, but a volt meter will show some indication. Remove the wire from the good gauge and read it with a 3 digit voltmeter, then do the same with the other one.. see if they are close.. I will look for the chart for temp/volt on thermocouples when I get back into town at the end of the week..

good luck

Dick

Dick, Yes I swapped the good gauge to the bad circuit sensor & wiring and still no reading. moved working good sensor & wiring to the "dead" side and reads fine. How can two sensors &/or two wire sets be bad???? My next trick may be to swap sensors in the engines left to right!! what a bummer!!:)