400 ISL - What is this sensor? No wiring connector attached.

[Bill R]

On 3/9/2023 at 4:11 PM, Ivan K said:

Well, it isn't what I expected, not for a switch, makes no sense to have a grounded pin. But, for a gauge signal, yes it could be a sender if there is a temp dependent resistance between the two pins, one of which is grounded. I measured 2.2k on a random sensor in my shop, room temp. One of your abandoned wires would also have to have a positive potential - not necessarily enough current for a test lamp unless LED. Something like in the picture. But as you said, it may not even be applicable to your coach if there is no missing function. I myself have used an old sensor just as a plug when testing engines on a test stand sometimes just because it was handy...who knows.

@Ivan K I finally got to the point of removing this, and you were correct in your assumption.  It is a VDO Temp Sensor, 120C, 6-24VDC.  This was stamped on the side.  Here is a link of one I found online.  Looks exactly like it.  https://www.genspare.com/show.asp?id=360

This was Monaco installed and I guess for other models than mine.  My temp gauge reads from the Aladdin, and is fully functional.  This is a thread grounded sensor as you noted.   500ohms at room temp and 200ohms at 210F.  The two wires going to this sensor was the 145 Temp Sensor Wire and a ground wire.  Interestingly, when I hooked up the ground wire to the thread ground terminal, I got an audible alarm behind the dash.  When I connected the 145 Temp Sensor Wire to the other terminal, the alarm went away. 

All this to say, this sensor is no use for my coach.  I figure while Monaco was prepping the engines in 2005 with these sensors, they did not know what coach the engine would be installed for and if it was needed.  Either that, or the various build departments had not quite made the production document changes to eliminate this sensor.  Sensor had a manufacturing date of 4/05. 

 

Edited April 29, 2023 by Bill R

[Ivan K]

Thanks for the follow-up, Bill. Interesting finding about the alert. I wonder if that could actually be what it's for but if you don't need it then all good.

[GringoScot]

Bill R. perhaps a "lifeboat" (or two) for me?  HOW did you get this VDO temperature sender out of the head?  What tool did you use?  I literally determined that this was a VDO (Czech republic) sender today after many an hour searching for such online from cell phone photos I took of the sender.  I cannot find a socket nor box end wrench with a wall thin enough to get between the valve cover and the sender.  LIFEBOAT please! Some background......I have a 2005 Monaco and I have been chasing a high (dash) temperature gauge issue since I became the owner 2 years ago.  I discovered that there was a "floating ground" to my dash gauges.  Each has new, individual grounds at this time.  I have a Scangauge D coming before my trip to Kentucky from San Antonio next week and this should give me the accurate reading, but having the dash gauge functional would be nice.  On my trip from Dallas to Illinois last year I was constantly downshifting when the gauge would drift at or over 200F.  I did all of the maintenance before that Labor Day trip (oil/filter, coolant/flushes/Simple Green, slobber mod, new thermostat and hoses, etc.) but the temp gauge has me borderline paranoid.  I can see from the cell phone photos of the the VDO sender that this is a 103C and I am curious if there should be a 120C sender instead and this is causing the high (calibration issue between 103C and 120C) dash temp gauge.

2nd LIFEBOAT, what is the thread size of your temp. sender?  1/2-14 NPT or NPTF? 

FYI, I noticed that the narrower spade wire (to the high temp dash lamp) was disconnected and coiled back to the plastic cable harness and I will have to get that reconnected once I replace the 103C with the 120C sender.  Thanks in advance.

 

 

VDO A2C59519516 Temperature and Press Senders.pdf

Edited May 24, 2023 by GringoScot

[Frank Bergamo]

Other than an open end wrench, could you grind a box wrench down to slip between the head/valve cover? You may weaken the wrench, but if you can get it around the sensor it just might break loose. Grinding a deep well socket might also be an option. Also, I would spray it with PB Blaster or something similar for 2 or 3 days before I attempted to break it loose. Hope this helps.

[GringoScot]

Frank Bergamo, thanks for the suggestions.  This was my plan tomorrow, if I did not find a narrow wall box wrench.....and my searches at the SA auto parts stores and Harbor Freight were not fruitful. If this tool mod does not work and Bill R. does not have any further suggestions, I may just decommission the current sender, remove an adjacent plug in the head and install the new sender there? 

 

Edited May 24, 2023 by GringoScot

[Bill R]

@GringoScot Here is a link to what I believe the sender is.  https://www.genspare.com/show.asp?id=360  I believe it is a 1/2" 14 NPTF but I have posted a pic below for confirmation.

To get it off I was able to slip a 7/8" shallow socket on it.  I had to bend the tabs to get it pushed down.  The socket was not all the way on but enough to get a good grip.  I then was able to put a socket extension into the socket, but since the socket was a shallow socket, I was not able to get the extension all the way into the socket either.  Needless to say, this was a first attempt to see if I could break it loose doing this, and it did fairly easily.  I did apply some PB Blaster to it as well.   I hope this helps, other methods have been suggested that were going to be my next step methods but I didn't need to.

Let me know if you have any other questions.

 

[GringoScot]

Bill R., thank you for the detailed removal instructions.  This was a concern: "would removal require 'subtle deformation' of the component?"  (A replacement component is about 2 weeks away from the other side of the pond and my trip is in a few days.)  Too, investigating the part number that you generously provided, the 103C (+/-3) that I misinterpreted as the sender max range is actually the alarm position for this sender.  Hence, my theory of an incorrectly installed sender, causing a calibration issue with the dash gauge, is debunked.  Seeing your photo and learning your removal process, I think I will run conductors from the sender unit, across the floor and to the dash temp. gauge and see if the value is more commensurate with the Scangauge D (that should be arriving today,) eliminating the wiring/connectors from the equation.  Again, a big thanks to you and Frank for your quick responses.

[Bill R]

@GringoScot Let us know how things go and glad to help.

One other comment, it is usually helpful to all of us on the forum if you put in your signature the year and model of your coach.

All the best in your troubleshooting.

[GringoScot]

Bill R., well a shower valve socket wrench did the trick.....(a few bucks at a home improvement store).

There is now a slight "twist" to this wrench 🙂, but "winner, winner chicken dinner"!

After cleaning the "green" contacts, I was able to test the sender in a bowl of hot water by the dash and my IR thermal gun proved the sender has seen better days.

I will plug the opening until the new sender arrives from across the pond, but at least I now know and the Scangauge D just arrived today....which should get this 2005 Monaco Knight 40PLQ from San Antonio to the Kentucky auto plant with an accurate coolant temperature reading.

Again, thank you and Frank for you assistance.

Edited May 26, 2023 by GringoScot

[Gary Cole]

Like your solution. I spent a considerable amount of time grinding a deep socket down to nearly nothing  when I pulled my sender. Not a perfect solution.  The problem with a standard  deep socket is that the top of the socket tapers and doesn't provide enough clearance with the upper portion on the sender. 

Edited May 26, 2023 by Gary Cole

[GringoScot]

Reference photos.......