Installing Tire Pressure Monitor System in Airsream Interstate

[jerhofer]

On our recent trip to Florida I had an issue with the inside rear tires losing tire pressure. And I wasn't aware enough to do more than give the tires a visual check as I could not tell by looking that the inner tires were flat. Since I obviously cannot be depended upon, I decided to install a tire pressure monitoring system to be my crutch.

I chose the Dill TPMS trailer kit for six tires. I found it at the Tire Rack and it was here within two days. The kit consists of six transmitters, a windshield mounted monitor, a 12V cord, a hardwire 12V cord and magnetic antenna extender.





There is a short antenna mounted on the monitor. Since this kit may also be used on a trailer, the antenna extender is used to get the signal to the monitor over an extended distance. Fortunately, the AI is short enough that I did not need the extender. If you do need the extender, there are two choices for getting that signal to the monitor. One way is to remove the short antenna and run the antenna wire directly to the monitor. The second way is to mount an auxiliary transmitter under the vehicle with its signal picked up by the small antenna on the monitor. Using the auxiliary transmitter would require running 12V to it but you would not need to run the extender cable inside the vehicle.

On taking the AI to my local tire guy, we soon discovered an issue with the Alcoa wheels. These wheels use a larger valve stem than standard. I called Dill Air Controls and discovered that they do make a larger valve stem. However, it would not work on the Alcoa wheels as the only one they make extends out about an inch and then has a 60 degree turn that is 2.5" from the bend. This valve stem would not work on either the front or rear wheels. The Dill service rep (very, very helpful) went to his engineers who recommended using a banding mounting system. This required buying four bands and the receptacle for the transmitter. Only four were needed as the inside rear wheels are Mercedes OEM wheels which use standard size valve stems.





While I was waiting for the bands to arrive, I decided to hard wire the monitor. I chose to attach the monitor to the windshield in the lower left corner. The main fuse panel is located in the driver's foot well. By pushing back the inside windshield post trim where it meets the dash, I was able to hide the cable and run it down along the side of the dash to the fuse panel.


With my voltmeter I found that fuse #21 was activated by the ignition. I am sure they existed for many years but it was only a couple years ago that I discovered the fuse taps shown below. They make it extremely easy to tap into a power line. The positive lead on the cable attaches to the red line on the fuse tap. To the left of the fuse block I found a pre-drilled hole that was perfect for securing the ground wire. After soldering everything, you simply put the original fuse in one side of the tap an then another fuse for the monitor. Plug the tap in and you have power.










The bands arrived today and, two hours later, we had them all mounted. This required removing the tires from each of the Alcoa wheels, re-mounting and re-balancing them. On the inner rear wheels we only had to break down the tire on the front side as the original valve stem could then be removed and replaced with the Dill unit. The tire guy says Ford uses this same band system in their wheels.

Now that all of the transmitters were finally in place, it was time to set up the monitor. First up is to choose the tire layout for your vehicle. 6a was the correct one for the AI.



The batteries in the transmitters (supposed to last 5-7 years) are activated once a speed of 16 mph is reached. The default base tire pressure is 35 lbs. To set the appropriate tire pressure for the AI, one holds down the R/D button for five seconds until it beeps. After the beep, you then push in the SET button. The monitor then automatically sets the base pressure as you drive down the road. The system goes to each tire and uses the inflated pressure to determine the base. In this case, I set each tire to 61 lbs and the monitor did the rest. It took about five minutes to hear the beep that indicated the base pressure had been set.

I drove about 30 miles so the tire pressure you see on the display below is higher than 61 as the tires heated up. To the right of the tire pressure is the tire temperature. If the tire temperature reaches 176 degrees, the system will beep and indicate the tire (or tires) that have reached that temperature. The system will also beep if the tire pressure is 20% lower or higher than the base pressure. On the left side of the display is an outline of the tire setup on your vehicle.





The actual cause of my tire pressure issues was that I had installed metal valve stem extenders onto the stock plastic extenders that come on the inside rear wheels. The centrifugal force of these metal extenders broke one of the plastic extenders and evidently flexed the stock rubber valve stem enough that tire pressure was lost on the other inside tire as well. Since the transmitter comes with metal valve stems, the flexing will no longer be an issue. I found a pair of 4" straight extenders that I mounted to the new valve stems and the fit perfectly. Checking the inside tire pressure now is a piece of cake.



This is not an inexpensive endeavor. The base system was $382, the bands and mounts were $158 and it cost me $80 for two hours of work by the tire company. Peace of mind...priceless! And I now know why truckers slap their tires with an iron bar!!!!

[73shark]

Nice write-up. Not seeing how the band works to hold the valve stem in the wheel while sealing the hole tho.

[Silver Goose]

On the 4 wheels where he used the bands, the original valve stems remain in place. The strap simply anchors the sensor to the inside of the wheel. That's why they had to dismount the tires to get full access to the wheel interior. Other vendors who use the strap method provide a sensor/battery pack that doesn't have the physical valve stem.

[jerhofer]

Originally Posted by Silver Goose

On the 4 wheels where he used the bands, the original valve stems remain in place. The strap simply anchors the sensor to the inside of the wheel. That's why they had to dismount the tires to get full access to the wheel interior. Other vendors who use the strap method provide a sensor/battery pack that doesn't have the physical valve stem.

You are correct. I forgot to grab my camera during the band installation as I was helping the tire guy.

[jerhofer]

One thing I forgot to mention is that, during my research on installing TPMS, I found in the Mercedes owner manual that TPMS is a factory option. If Airstream is not ordering this option on their new units, they should be. It would be great to have the tire monitoring system integrated into the other operating systems.

[KJRitchie]

I went with the easier way, TireTraker. Sensors screw onto the end of the valve stems and reads pressure and temperature. Probably not as accurate for temperature as the Dill but seems to work well enough. Tire pressures seem accurate when compared with a tire pressure gauge. I take the sensors off when in storage and remove the batteries. I just didn't want to have to bother taking wheels and tires off and trusting a tire shop to jack my Airstream up correctly.

I had one sensor go bad but they replaced it under warranty with fast shipping.

Kelvin

[Protagonist]

Originally Posted by jerhofer

One thing I forgot to mention is that, during my research on installing TPMS, I found in the Mercedes owner manual that TPMS is a factory option. If Airstream is not ordering this option on their new units, they should be. It would be great to have the tire monitoring system integrated into the other operating systems.

It's only a factory option if you use the MB steel wheels, not for aftermarket Alcoa aluminum wheels. Since OEM TPMS is integrated into the OEM valve stems, factory TPMS will not work with the thicker metal of the Alcoa wheels.

On the Sprinter 2500s, it's not even optional; it's mandatory due to the 2500's GVWR, according to Federal Motor Vehicle Safety Standard (FMVSS) 138.

[Boxster1971]

Originally Posted by Protagonist

It's only a factory option if you use the MB steel wheels, not for aftermarket Alcoa aluminum wheels. Since OEM TPMS is integrated into the OEM valve stems, factory TPMS will not work with the thicker metal of the Alcoa wheels.



On the Sprinter 2500s, it's not even optional; it's mandatory due to the 2500's GVWR, according to Federal Motor Vehicle Safety Standard (FMVSS) 138.

There is no factory option for a TPMS on the 3500 Sprinters. If you look at the info in the owners manual it is only for a 4-wheeled Sprinter. The TPMS is only on the 2500 models because it is required by USDOT regulations cited above by Protag. That may change in the future because USDOT is trying to get the regulation extended to all vehicles, especially large trucks.


- - Mike
2013 Lounge EXT on 2012 Sprinter

[k9jackie]

Wow that is surprising... I just assumed it would be there on a MB

[hamiltonmj]

This is a great post!!! I've been wondering how to do this and VOILA, someone posts a narrative with great pictures...thank you.

[jerhofer]

Originally Posted by Boxster1971

There is no factory option for a TPMS on the 3500 Sprinters. If you look at the info in the owners manual it is only for a 4-wheeled Sprinter. The TPMS is only on the 2500 models because it is required by USDOT regulations cited above by Protag. That may change in the future because USDOT is trying to get the regulation extended to all vehicles, especially large trucks.


- - Mike
2013 Lounge EXT on 2012 Sprinter

I stand corrected. I did not read far enough to get all the info.

Even if Airstream cannot order the option from the factory, they could do something similar to what I have done. They already have four of the six tires removed in the process of installing the Alcoa wheels so they would not be adding much additional labor time to installing the transmitters. To make it look more professional they could build the display monitor into the dash which would involve some design work, a small amount of labor and the running of the 12V wiring. If they offered it as a stand alone option, I would bet it would be on at least 90% of the AI's.

[Boxster1971]

Originally Posted by jerhofer

I stand corrected. I did not read far enough to get all the info.

Even if Airstream cannot order the option from the factory, they could do something similar to what I have done. They already have four of the six tires removed in the process of installing the Alcoa wheels so they would not be adding much additional labor time to installing the transmitters. To make it look more professional they could build the display monitor into the dash which would involve some design work, a small amount of labor and the running of the 12V wiring. If they offered it as a stand alone option, I would bet it would be on at least 90% of the AI's.

I agree. Airstream should install a TPMS or at least make it an option. They are added to the Sprinter B-van converted by Advanced-RV as standard equipment.


- - Mike
2013 Lounge EXT on 2012 Sprinter

[cwhaye1]

before I bought a monitor I took the truck to b&b tire shop in rock hill sc. they said I have four aluminum wheel vlve stems and the two inner auto rubber valve stems on the back two. so I ordered 4 transmitters for the aluminum and
2 rubber transmitters, after calling tire minder. these were installed and appear to be working.

[73shark]

Originally Posted by cwhaye1

before I bought a monitor I took the truck to b&b tire shop in rock hill sc. they said I have four aluminum wheel valve stems and the two inner auto rubber valve stems on the back two. so I ordered 4 transmitters for the aluminum and
2 rubber transmitters, after calling tire minder. these were installed and appear to be working.

Welcome to the Air Forums.

What brand did you get?

[cwhaye1]

tire minder

[c21]

Originally Posted by 73shark

Welcome to the Air Forums.

What brand did you get?

A much easier way to go is Truck Systems Technologies TPMS. They have an RV specific system that is very easy to install. The screw-on sensors detect both temp and pressure and they are easy to code to their tire location. They also have user replaceable batteries. The monitor can be hard wired or will run for a week or more on installed battery which can be charged with an included cig lighter plug. It will support up to 22 sensors, I bought 8 with mine, 6 for my AI two more for a trailer I occasionally pull with my motorcycle in it. The monitor cycles thru each tire for about 5 seconds reading out temp and pres. (you can set the monitor to not cycle thru the trailer tires when the trailer is not along). Alarm set points are user adjustable for each axle. Very affordable and easy to use system.

[Protagonist]

Originally Posted by c21bill

It will support up to 22 sensors, I bought 8 with mine, 6 for my AI two more for a trailer I occasionally pull with my motorcycle in it.

Get two more, one for your Interstate spare tire, one for your trailer spare. Spare tires sit and sit and generally get ignored until they're needed. That's the wrong time to discover that your spare is also flat.

[c21]

Originally Posted by Protagonist

Get two more, one for your Interstate spare tire, one for your trailer spare. Spare tires sit and sit and generally get ignored until they're needed. That's the wrong time to discover that your spare is also flat.

Leave it to Protag to come up with an excellent idea!

[Boxster1971]

Originally Posted by c21bill

A much easier way to go is Truck Systems Technologies TPMS. They have an RV specific system that is very easy to install. The screw-on sensors detect both temp and pressure and they are easy to code to their tire location. They also have user replaceable batteries. The monitor can be hard wired or will run for a week or more on installed battery which can be charged with an included cig lighter plug. It will support up to 22 sensors, I bought 8 with mine, 6 for my AI two more for a trailer I occasionally pull with my motorcycle in it. The monitor cycles thru each tire for about 5 seconds reading out temp and pres. (you can set the monitor to not cycle thru the trailer tires when the trailer is not along). Alarm set points are user adjustable for each axle. Very affordable and easy to use system.

I also have a TST TPMS. They have great customer service. I first bought an internal sensor system, but when I had trouble getting it installed they exchanged it for the flow-thru external sensors and refunded the difference.