Installing Tire Pressure Monitor System in Airsream Interstate


2/12/15

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.

2-4-15 TPMS 2 2-4-15 TPMS 3

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.

2-11-2015 tpms 9 2-11-2015 tpms 8

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.

2-11-2015 tpms 4 2-11-2015 tpms 2-11-2015 tpms 10 2-11-2015 tpms 3 2-11-2015 tpms 2

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.

2-4-15 TPMS

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.

2-11-2015 tpms 6 2-11-2015 tpms 5

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.

2-11-2015 tpms 7

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2 Comments

  1. Jerry, I have been thinking about the exact same set up for my Ram 3500 Dually, kinda surprised its not standard on the Longhorn edition. Since I have the factory Alco wheels I’m guessing I will need to follow the steps you laid out here. Thanks for post, tell Sharon & Matt Hello.
    Bill Sheley

    • Good to hear from you and glad this project can help you.


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