EGT sensors, are they mechanical or electrical?

[kisongo]

I have a 912 with 2x EGT sensors, I am not sure if they are mechanical or electrical, however the gauges are not reading anything. Are these mechanical or more likely electrical ones, how can i fix them or is it just a replacement?
I don't have a skydat, the gauge is a simple gauge with 2 needles- if that helps?

[Duck Rogers]

Egt sensors are "electrical"
The layman's explanation: It consists of two different types of metal wires wound together that generate an electrical current when they are heated up. The gauge is a simple millivolt meter with a different faceplate and the needle deflection is actually the amount of millivolts generated.
If your gauge is not showing a reading the chances are good that the probe is kaput. There are no "positive and negative" connections to the gauge, only the 2 wires that go into the probe. The gauge NORMALLY doesn't pack-up, but it's not impossible.
Also known as a "pregnant" device. It either IS or it ISN'T working........

If you have one gauge that measures both probes (dual gauge) and neither of the needles are deflecting, I would suspect the gauge. It's unlikely that both probes are kaput at the same time but again, it's not impossible as I don't know the circumstances that led to the device not working.

Hope this answers your question

[kisongo]

OK, that helps..It has 2 probes (left and right) and one packed in long before the other. I guess I have to eliminate the problem: it could be the probe, the cable or the gauge. I do not think the gauge is the problem (as one was kaput for a while then the next).
In order to help eliminate the cable and the probe, if the cable is OK, should I be able to measure a current near the probe? You said there are 2 wires, are these coming all the way from the gauge, or one from + terminal and one to the guage?
On some systems, if one touches the cable to the earth direct, it should see the gauge respond immediately ( as the gauge is measuring the resistance from + and -).
If current gets as far as the probe, then one can only assume the cable is OK. If no current, then replace the cable...is this logical.
I am in Tanzania, so I am trying to find the solution before I have to order the complete unit from SA.
Thanks

[Duck Rogers]

Dude, you're creating a lot of confusion for yourself.
There is NO current flowing in that cable unless the probe is heated up REAL good and then it's MILLI-VOLTS.
There is no + and - even though the "cable" consists of two wires.
From what I gather you said it looks like the gauge may be ok, then all you need to determine is whether the probe is ok or not and in most cases the probe and cable is one-piece. They cannot be seperated unless you have a "cable extension" connected to it in order to make the cable longer.
If you really insist on testing the cable, then DISCONNECT the probe (and cable that is attached to it) from the exhaust AND the gauge. Seeing as the two wires are twisted together on one end that are encased in the probe, you can take a MULTIMETER and measure for continuity (or resistance, call it what you will) on the two other ends that normally connect to the gauge. Set the multimeter to OHMS setting and measure across the two ends of the cable. If there's a reading on the scale, the wiring is PROBABLY good. (use of the word "wiring" here includes the probe) If not, get a new probe. It comes with the 2-wire cable attached.
My guess is the probes are no good. Replace them.

Picture this: 2 equal lengths of wire. On one end the insulation of each wire is stripped off and the 2 bare pieces are twisted together and encased in a protective metal tube (this is the probe) The other 2 ends each get connected to a meter. That's it. Nothing more, nothing less

[kisongo]

Thanks, and that is very helpful. I will take a closer look and see what I can do.Sounds like I will have to order some complete units.

[nickjaxe]

If you have a heat source ie oxy acet welding torch...or a small propane torch you can test the probe,

With them removed from the manifold just heat till red at the very tip....if they are working you gauge will ind a temp,


Nick.