The EGT for my truck (DIESEL) cost $185 and it is a single. It uses 12 volts and is VERY steady and very accurate. The duel one that I bought for the boat cost $135 and it is a joke. I used the K type thermocouples only with my FLUKE digital meter.

Let me get this straight.. you swapped good gauge to bad side, no reading.. ok.. problem is still on bad side.
Moved working good sensor & wiring to the "dead" side and reads fine. Does this mean you took wire from good side and put it on the bad gauge? If so that tells me both your gauges are good.
Or did you take the wire and sensor from the bad side to a known good gauge?
How many wires go to the back of each gauge? Two from sensor, one from 12v for light, and ground?
Try switching sensors and see what happens.. Does the sensor have a 25' lead on it or is there a connector in line with it by the thermocouple??

It would be nice to have a known good gauge that you could move around to check at different points, like a volt meter. That way you can see a go/no go situation..

Tinkerboater,
are both gauges you are speaking of using an exposed tip type of thermocouple? The exposed tip will react much quicker.. just curious.. What brand of gauges are you using anyway..


Dick

Mr gadgets,
Yes, you are correct in everything you said. The bad side has never indicated on a known good gauge, then I replaced the sensor - no change... then I changed the wire ( a 25' Gaffrig wire). There are 2 bolt & nut connectors on leads of cable & sensor (again-Gaffrig sensor). still nothing on any good gauge!!! I am really exasperated :( especially after melting the other engines piston..... this new sensor is somewhat longer than the original also. thanks!!

ok, you have a sensor, then the connection to the 25' lead, with two bolts and nuts? You replaced the gauge with a known good one, and it didnt work. Then you changed the thermocouple, still NG. Then you replaced the wire (25'), still no good.. Ok, take the good gauge, old wire (if it isnt still in the boat) and old sensor. Hook it up and put a match to the end of the themocouple.. You should see a reading. If not, try another sensor, if ng, try the other (new) wire. If the wire seems to be good and the sensor seems good, use a match to heat the thermocouple.. That way you eliminate the engine as a problem..
Now make sure you are safe with the open flame.. you know..gas fumes..etc.

I would also try to connect the thermocouple without the 25' wire.. see if it works then. That is if hooking it up that way is possible..

Dick

I would try MRG.'s idea of heating up the themocouple with a match & take the engine out of it. Sure hope that the engine is OK. I know I ran with a dead cylinder once & only way I knew it was that motor was running with more boost when I was crusing than before.

Dick--- The EGT that I bought for the boat is a WESTACH. It is junk -the needles bounce when you hit a wave. I used the thermocouples along with my FLUKE meter. Works great and reads out in digital with memory recall. The one for the truck is a VDO and the needle doesn't move when you hit a bump. I thought it was bad when I started the truck since it was reading 250 DEG,s on the peg ( lowest reading is 250 ) I didn't realize that a diesel idles at that temp. My boat idles at 750-850

i'm sure everyone knows this....how a TC works is to dissimilar metals touching ALWAYS produce a voltage...as temperature changes so does the resistance. hummmm hence corrosion. so they need no outside power. your TC lead (wring to the dash) MUST match the TC installed...i have had very little luck, long term, with TC's sold to the general public. i now use VERY high quality ones...which i can also swap out in less than 15 seconds if one fails.

placement is very critical as well!!!!

audacity, all components are by the same maufacturer- Gaffrig.

Mr. Gadgets, I am going to try an industrial heat gun on the thermocoupler to see what happens. You cannot connect the thermocouple directly to the gauge however (dang it!!) That nut & bolt thing is the problem, they are VERY small machine bolt & nut. :)

Tinkerboater,
I see what you mean now.. cheap meters dont like bumps..!! :D

blown formula,

I found the chart for K type TC's.. at 500 degrees, you should see 10.56 mv.. or .01056v. At 1000degrees 22.250mv not much change and definitely need a good digital volt meter. But with a go/nogo you test you should see some change from room temp to high temp.
The exposed tip type TC's are the fastest reacting, because they are exposed, but they dont last long.. If there is a case around the TC it will take a while for it to warm up.. The match or propane torch works wonders, but you have to be careful not to melt the insulation on the wire..
At least you will take the motor out of the equation. Good luck and let me know how it works.

Dick

I spoke to the Livorsi Tech line today. They said their TC will output as much as 3-4 volts & can be read on a multimeter!! That's a real surprise after reading other threads about T.C.'s & EGT's. He said to do the "DUMB" test with a lighter or heat gun. I did not get a chance last weekend .....so I will do it next fri or sat.
Tinkerboater.... Gaffrig EGT gauges DO NOT BOUNCE in rough water! That's a fact!:D (at least the dual gauge does not). :)