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Topic: Air pressure sending unit where do they ground at? (Read 1067 times) previous topic - next topic

Air pressure sending unit where do they ground at?

Working thru issues.
Replaced both senders (front & rear air tanks) and they worked.
Then the rear tank gauge quit again, so replaced that sender again, still no joy but noticed that both gauges would "blip" (drop nearly to zero at the same time) intermittently...
so next thing to check is the ground wire(s)
My schematics page shows that the grounds are tied together @ a ground terminal.
Question is ....Where on the coach is the terminal???
Thinking it may be after it enters the interior at or near the banks of reset relays in front of the passenger seat... or is it closer to the alarm in front of the driver??
thnx
red
'02 40' U320t  4010WTFS Build 6036 1 slide
Motorcade # 17841
SKP 151920
Retired truck driver
 5 million miler
Still have itchy feet for travel

Re: Air pressure sending unit where do they ground at?

Reply #1 –
Wouldn't it be just as easy to add another ground? Don't think it could hurt?

Re: Air pressure sending unit where do they ground at?

Reply #2 –
Quote from: DavidS –
Wouldn't it be just as easy to add another ground? Don't think it could hurt?
Have several grounds that ain't up to snuff... so all may be tied to the same ground terminal.
'02 40' U320t  4010WTFS Build 6036 1 slide
Motorcade # 17841
SKP 151920
Retired truck driver
 5 million miler
Still have itchy feet for travel

Re: Air pressure sending unit where do they ground at?

Reply #3 –
are not those gauges grounded under the lift up dash panel like on all other models, mine are there?
JohnH
Coachless, now use aircraft. 2003 Ford Travelair TC280 class C. Super shape. Just for 1 yr .
1994 Ford E350 ClassC,total renovation inside and out. Now sold.
2000 U295  36' Cummins 350 c/w Banks Stinger, Resonator upgrade,Solar, LED lites.Residential fridge with slide out pantry. Build 5674. Sold
ex 92 GV 022C ored Cummins. Sold
ex 95 GV240 cat 3116. Sold
2017 Mini cooper s & 2016 land Rover LR2 HSE  LUX.
jhaygarth@aol.com    SKP #130098
treat everyone as you would like to be.

Re: Air pressure sending unit where do they ground at?

Reply #4 –
My schematics drawing shows that the sending unit "green" wires are terminal grounded and the dash gauge is also grounded.
Hope to find where the wire looms enter the interior of the coach and then just follow them to the dash area..
OR may have to start at the alarm doohicky and follow wires in reverse... I'll figger sumpin out.
Our coach has VDO gauges but use a Stewart-Warner 2 wire sending unit as per FT shop.
The white or red wires are powered and go via the junction box (power/gauges/alarm) to each respective component.

red
'02 40' U320t  4010WTFS Build 6036 1 slide
Motorcade # 17841
SKP 151920
Retired truck driver
 5 million miler
Still have itchy feet for travel

Re: Air pressure sending unit where do they ground at?

Reply #5 –
After leaving MOT I had air pressure gauge trouble.  The front registered 90 and the rear 70.  They had been under the dash moving wires. 

When I got home I unscrewed both senders and the tanks were at 130 on a manual gauge which is about what they always run. 

Called MOT and discovered there is a Stewart Warner box under the dash that both senders pass through on the 2002.  I looked briefly to find the box to check the connections but didn't find it and don't know exactly what I'm looking for.  After moving things around the front gauge is 120 and the rear 100 so I'm sure there is a bad connection somewhere there. 

If you find that box please send a photo or description of it.  I bet that's where both our problems are.  It will be weekend before I can mess w The it again.
Rick & Rhonda
2003 U320 4220  Build #6199
Was
91 36' GV 300 Caterpillar, 92 40' U280 300 Cummins, 97 36' U295 300 Cummins, 2002
U320 450 Cummins
(Guess we're hooked)

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Re: Air pressure sending unit where do they ground at?

Reply #6 –
Quote from: Johnstons –


 discovered there is a Stewart Warner box under the dash that both senders pass through on the 2002. 

If you find that box please send a photo or description of it.  I bet that's where both our problems are.  It will be weekend before I can mess w The it again.
OK thnx for the info... If I do not find it will be @ MOT the  17th... will have them fix it as well as straightening out the touch pad boo boo I did.
Will have them show me where the box is and take a pic or two.

red
'02 40' U320t  4010WTFS Build 6036 1 slide
Motorcade # 17841
SKP 151920
Retired truck driver
 5 million miler
Still have itchy feet for travel

Re: Air pressure sending unit where do they ground at?

Reply #7 –
Quote from: Johnstons –
I looked briefly to find the box to check the connections but didn't find it and don't know exactly what I'm looking for.  After moving things around the front gauge is 120 and the rear 100 so I'm sure there is a bad connection somewhere there. 

If you find that box please send a photo or description of it.

I suspect it is the "blue module" that you're looking for (note per Roger it may also be grey). 

Photo in this thread air gauge on 2003 U320

"Blue Module" Failure
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320

Re: Air pressure sending unit where do they ground at?

Reply #8 –
Rick, your box is probably blue.  Your pressure sender signals go into the box and then from the box to the gauge.  The box probably supplies the reverence voltage to the transducer (pressure sensor) and then tests for alarm conditions and passes some signal to the actual gauge.

If the gauges stop working it is much more likely that something in the gray/blue box has failed.  They are not replacable and as far as I can tel unrepairable.  Both of my air gauges quit at the same time.  I replaced them with direct read mechanical gauges which I like much better.  With no electronic gauges the alarm will ding forever, a switch in the annunciator line takes care of that.  But then there are no turn signal beepers.  A couple of diodes and connections to the sterring wheel harness and they are back.

If it is a bad connection, unplug every connection, add a bit of dielectric grease and reconnect.  It should help if that is the problem.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Air pressure sending unit where do they ground at?

Reply #9 –
Here is my schematic
It shows that the ground(s) are joined at a terminus point, and just the power wires go to the other connection boxes..
No idea why it rotated 90 degrees
'02 40' U320t  4010WTFS Build 6036 1 slide
Motorcade # 17841
SKP 151920
Retired truck driver
 5 million miler
Still have itchy feet for travel

Re: Air pressure sending unit where do they ground at?

Reply #10 –
So where do you put the switch to stop the ding ding when the gauges are replac d with mechanical air gauges?? My coach has had them replaced and now I know why it's ding dinging
2003 U320 4220 42' Tag Axle
"Babe The Big Blue Ox"
Motorcade #18069
🤔Mark and Angela Bumgarner 😎

Re: Air pressure sending unit where do they ground at?

Reply #11 –
Quote from: pressuresolutions –
So where do you put the switch to stop the ding ding when the gauges are replac d with mechanical air gauges?? My coach has had them replaced and now I know why it's ding dinging
I just clipped the ding ding wire, and haven't got back to figure out how to make it not ... got to be a wire  going to that blue/gray box (that I as yet haven't found)
Still Fighting toilet/AquaHot/hyd leak in the slide/leveling issues and broken windshields first.
Then will deal with the ding ding,& rear view camera malfunctions.
'02 40' U320t  4010WTFS Build 6036 1 slide
Motorcade # 17841
SKP 151920
Retired truck driver
 5 million miler
Still have itchy feet for travel

Re: Air pressure sending unit where do they ground at?

Reply #12 –
I replaced mine but zip tied my electronic gauges behind the dash hooked up. It stop the dinging for ten plus years.
2025 Wanderbox Outpost 32 on F600 Expedition Motorhome
2015 Born Free Royal Splendor on Ford 550 nonslide version  for sale
Former Coaches  covering. 360,000 miles
1999 34 U270
2000 36 U320
2001 42' double slide U320
2018 Jeep Rubicon
 

Re: Air pressure sending unit where do they ground at?

Reply #13 –
Quote from: pressuresolutions –
So where do you put the switch to stop the ding ding when the gauges are replac d with mechanical air gauges?? My coach has had them replaced and now I know why it's ding dinging

Look for (maybe just find by sound) the offending dinger. Mine was to the left in the jumble of wires not attached to anything.  It's about 1 1/4" in diameter and an inch long, black. One end has wires connected to it the other has a turnable end that opens or closes the holes to let more or less sound out.    Yours may be different.  Cut either wire to add in a switch.  I used a round 12v switch that fits in a 3/4" hole.  I put the switch in the lower section of the dash panel to the left of the steering column.  It is pretty much out of sight.



These switches are to the right of the steering column, same area to the left for the ding-off switch.

Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN