New engine, old pyrometer, no work!

[Larry Backman]

repowered from one QSM 670 to new one and kept my old instrumentation, pyrometer, water flow and raw water heat alarms.  The 2 raw water alarms made the cut, the pyrometer did not.

 

i have power to it (lights up with ignition on) but the needle never moves past 90 degrees.   When the I nine came out the probe was removed and put to the side, no wires cut, the gauge was unplugged at the dash, clipped at the 2 12 volt leads and then reinstalled into a new panel.

 

suggestions where to start or just throw the whole kit away and start fresh with a new one?

Topic

[Corey Schmidt]

That’s great news… glad you got it sorted out!

[Larry Backman]

Ha! Thank you Corey, you were spot on.  A twist and tug to the connector, a shot of dielectric grease and hurray, I have a working pyrometer again!

 

 

[Corey Schmidt]

Larry, hard to tell if it’s our gauge without seeing the front of the gauge… however, it does appear that one of the sockets on the connector was pushed back as you suspect?

Maybe use some di-electric grease, reset that one pin, and give it a go again?

If it is our gauge and that pin is not fixable and ends up being the culprit, I can send you a replacement pigtail free of charge…

Let me know…

[Larry Backman]

Actually a Hewitt gauge with a 4 pin connector.  I think the problem is that the yellow female pin socket in the connector is pushed back and not making contact with the gauge pin.

 

im going to try and borrow a probe and wire it up to the gauge and see what happens.  Easier than cutting splices and trying to do an ohms test across 20′ of wire with the winds far apart!

 

is this your gauge?  Here is the pin connector also..you can see the lower left connector is back in the plastic housing.

 

[Clark Leighs]

Do as Corey suggests first.

No dice?, then Do an ohms test of the leads.   If the wiring , the yellow and red leads, are continuous it will show an ohms reading.   Ohms would indicate the wiring and the T.C. itself are ok.

If it shows open or infinite then one of the two leads are broken somewhere or the thermocouple [T.C.] itself is monkeyed.

Check inside the plug that a lead is not broken or loose.

 

If it appears the  T.C. or wiring is at fault  then a new T.C. should be available if that is the case.   It should be possible to get a suitable one from Seaboard as these things are all ‘K’ types that I know of. Just get the right size.

 

[Larry Backman]

It’s an Isspro gauge and I think an SMX probe.  I’m confident the wiring was not disturbed, I’m not confident in either the probe or gauge.  The gauge had a little square plastic plug that carried a thick grey wire and 2 thin #18 wires into the gauge.  The #18 wires go to +/- 12V, the grey wire goes to 2 undisturbed butt connector splices to the probe.

 

i will solve the mystery this weekend.

[Corey Schmidt]

Larry, if you pull the probe out of the mixing elbow and put a lighter flame to the very tip of the probe, what happens on the gauge? Any reading at all? If there is 100% no readings, then you either have a bad gauge, wiring, or probe. I would suspect the gauge first if you’re very confident in the wiring.

Is this one of our SMX EGT gauge kits? If not, I may need to see some pictures of how the gauge is connected on the back…

There is no power input required for the gauge to work as the thermocouple probe transmits a very minute voltage (mA) on it’s own that the gauge can interpret. Testing the signal accurately requires a special device.

Corey

Isspro EGT Pyrometer Testing machine

[Larry Backman]

Trying to avoid doing something stupid till I need to.  This would have been so much easier if I had the brains to ask for it to be tested before put back in place!

 

the probe is in the exhaust fitting, the wiring was never cut, the gauge was disconnected via its plug, then plugged back in and rewired to 12V.  The red and yellow leads are presumably in the grey encased wire that leads from probe to dashboard.

 

The probe was handled more carefully than the gauge which i recall had a weird reading at one point or other when we were fitting it into a new Dash panel.

csn I unclip the plug and do a test on the red and yellow leads to see if I get different readings with engine off and engine on?  Likewise, is there any test I can do at the gauge leads to see if the gauge responds to a stimulus without actually being connected to the wire?

[Corey Schmidt]

Larry,

If it is a single engine pyro gauge the setup is simple…. the 12V+ used is only to light the gauge and nothing else. You will need to test the yellow and red wires first for continuity… then if all is good there, test the pyro with a lighter.

Check out this video on how to test a pyro gauge:

Seaboard Marine – How to test a Pyro Gauge

Let us know how it goes!

[Author]

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