Transmission temperature sender

[crah]

My temp gauge on my dash works normally, but after I drive for an hour or so, the gauge will bounce erratically from normal temp to overheat and keep bouncing up and down. Every once in a while it will work normal. When back to a stop it usually goes back to normal. This all started about a year ago after I changed the fluid and filter. The transmission allison 3000 works flawlessly. I did a search and found what looks like a sending unit on one of the coolant lines but there is no wiring hooked up. The piece looks like a small block around the line with a small nipple type protrusion. It matches the picture I've seen on this forum. I'm not sure where my gauge is getting the temp from but obviously it can't be from there. I don't believe this is an aftermarket gauge. Everything seems factory. Anyone else know a possible place the sending unit could be or why the gauge bounces. It only bounces after prolong drives of hour plus and always goes back to normal at idle.

[8.3Oilbuner]

Hi Crah; Sounds like you have found the location where the transmission sender is located on one of the cooling lines. Mine is the same place on my 01 Windsor with the 3000 series transmission. Is it possible that the wire with the clip on the end that attaches to the sender has detached and has been blown upward next to the transmission and is intermittently grounding itself on the tranny or another metal component making the gauge jump to different readings. I know of no other place where the transmission temp sending unit is located. Others here on this forum who have had their temp gauge not work have found the clip on the end of the wire gone or the clip had become detached from the sending unit and has been blown upward by the force of air when the coach is in motion??? Just an idea to shoot your way.

[CountryB]

Another possibility is that previous owner (if there was one) had a problem with the sender unit on the tranny cooler line and then relocated it to the factory Allison sender unit (the one that provides the Allison ECM temp readings).

He may have just spliced the dash gauge wire into the ECM temp wire (which I think would be a bad thing).

[crah]

Thanks all. I will take a picture tonight. I do recall seeing a wire near that was coiled up about 6-8 inches away. If it's not connected, I'm assuming there is no way the sender can send a signal to the transmission so not sure how the gauge is working. I'm the 2nd owner so precious work could have been done.

[crah]

Ok got a couple of pictures. First picture is what I'm presuming to be the sending unit. 2nd picture is the hanging wiring with the electrical tape on the end. It was coiled up higher than shown in this picture but I pulled it down to get a better picture of the wire. 3rd picture is a close up of the wire. I didn't see anyway this wire could connect to the sender. The wire almost seemed to be a 12 volt terminal end. And I don't see how muly gauge ever worked at all where the wires was bundled up. Any insite would be appreciated.

[vito.a]

Our trans temp gauge was also erratic going down the road. This is a common issue on these coaches. The wire for our gage clips onto the sending unit shown in your first two pictures. The connection was fairly loose, so I crimped it slightly and added some wire ties to hold it securely to the trans cooler hose. It now works great.


Mike may be correct as I don't understand how your gauge can function if it's not connected to the sending unit. There are lots of extra wires in these coaches, so be careful connecting the wire you found to anything until you check both voltage and resistance to ground.

[8.3Oilbuner]

Good afternoon Craig; finally got my grubbies on and crawled under my 01 Windsor. The pictures you have posted with the wire that is taped up is in the exact same location on my Windsor. The wire goes up the passenger side of the transmission and is zip tied to a spare mounting hole on the trany. It is enclosed in the crinkle tubing just like your picture. The wire and tubing continues up just behind the air dryer and then into the harness along the frame. I am going to go out on a limb here, but I bet that loose wire is the one to your transmission temp. gauge on your dash. I could see no harm as to attach it to the sender on the cooling line and see what happens. If this was my coach I would give it a try, but you need to be OK with doing that. You could idle in gear for about 5 to 10 minutes and see if the gauge climbs as it should. As I posted before, do not know of another place to get that reading from unless the previous owner had it moved to another location. Your gauge for the transmission temp on the dash could be getting the reading you have posted by a possibility of not a good ground to the dash gauges. Mine do all sorts of weird stuff when you just turn on the headlights. I have read about Monaco not using a large enough wire to ground the gauges and you can get grounding through different gauges. If you hook the wire up and you get a reading, let us know. I have no other idea on why that wire in your posted picture is just hanging there.

[oldguy70]

The end of my sender was corroded away so I had to get a new sender and put a new clip
on the wire. Why you are getting a reading at all must be the wire from the gauge is getting grounded some how.