Pyrometer and Pressure

jmacstack · 05-30-2011, 01:31 PM

We are in Rapid City, SD and along the way I noticed my pyrometer was working intermittently. It's acting like a loose wire. Any ideas on where I might look for that on the engine? The pressure side (dual gauge) is working fine. So far so good on everything else except that I have a leaking passenger side window that leaks only when we are not moving. It's been raining the whole way from Montana! Thanks, Jennifer

2dogs · 05-30-2011, 08:47 PM

Jennifer, The sending unit is on the drivers side coming out of the exhaust right after the turbo. on our 87 it was working intermittent, sounds strange but if i tap the air horn it works again! Brian

encantotom · 05-30-2011, 09:59 PM

to help visualize it. the pyrometer is just a sensor(k type thermocouple) that threads into a collar that is a little smaller than a dime that is welded either directly on the turbo housing or more commonly on the exhaust right after the turbo. if you have exhaust blankets covering it there might be a hole in it where the sensor or at least the wire sticks out. the 2 wires (one for plus and neg) will run directly from there up through wire tunnels up to the dash where it hooks directly to the gauge (or to a amplifier box right by the gauge) btw, honking the horn should have nothing to do with it unless there is a loose connection at the dash. the pyrometer sensor sticks through a hole in the exhaust (or turbo)

it is a very simple system with only 3-4 parts. 1. the sensor (k type thermocouple) 2. the wires 3. the gauge itself. 4. the amplifier box

so, if honking the horn makes it work, either it is the biggest coincidence in the world or there is a loose connection up front since the horn vibration shouldnt shake anything back at the engine.

possible the gauge itself or amp box is bad, but less likely than a loose connection.

i installed the pyrometer on mine myself. i also have on one my ford powerstroke pickup. very useful if you use it.

on my newell, the instrument panel had a lot of shared ground wires. i actually ran some additional ground wires from the front main dc panel and have used them for some additional grounding.

loose ground wires on the gauges i think are a common problem for our vintage coaches.

but i have to say that honking the horn is a great first try and certainly the easiest. its kinda like hammering on something with your fist. but sounds better. nothing like the sound of a newell air horn. i always do mine in underpasses.

happy troubleshooting

tom

folivier · 05-30-2011, 10:25 PM

Tunnels, air horns, and jake brakes! Now you're talking!

encantotom · 05-30-2011, 11:11 PM

i have to admit besides always tooting the air horn in a tunnel, i love to hear the jake brake....

tom

chockwald · 05-31-2011, 12:41 AM

You, too?

I just love hitting the airhorn in, or out of a tunnel. I love listening to the jake brake....I remember on family trips in the late 50's early 60's to Idaho I would love hearing the jake brakes at night as we slept in a roadside motel along the way....it meant we were traveling, which I loved to do then, and now! Good memories!!!

Quote:

Originally Posted by encantotom

i have to admit besides always tooting the air horn in a tunnel, i love to hear the jake brake....

tom

2dogs · 05-31-2011, 04:04 AM

Just saying that it worked.. might be a ground issue? when it dosnt work i tap the horn presto and i also love the jake, ours was hooked up one side only [low] so i ran another wire. now have low/high Brian

encantotom · 05-31-2011, 04:19 AM

i believe it worked. but there is always a reason. the old chrysler van i had my kids drive in high school had a cold solder joint on the dash. sometimes to get the car to start you had to pound on the dash....same thing....

gotta love those airhorns and jakes.

tom

folivier · 05-31-2011, 11:52 AM

"the old chrysler van i had my kids drive in high school"

Wow, that's tough love!