Plastic Surgery

When you take a saw to your dash it is always a little unnerving - there is no turning back. But in order to install a double DIN chassis stereo into the truck it had to be done.  It all seemed to work out. The new stereo provides better connectivity to our iPhones, including Bluetooth, and gives an updated look to our 10 year old truck.

A climate control system problem received a temporary fix so that things are functional enough for the trip. Read on, especially if  re-circulation, blending and vent flow controls are your thing.

Recently the trucks air conditioning has been only marginally effective.  We were concerned that it was not going to be up to the task during our summer travel.  The first thought was that it needed to be recharged, Recharging helped some but the amount of air flow was just not what it had been in the past.  The fan made lots of noise but not much of a breeze.  In addition, the re-circulation setting didn't seem to make any difference, either off or on.

What we discovered is that Dodge trucks have a weakness in their climate control system.  There are 5 flap/doors used to control air temperature and flow.  There are 4 DC servos that control these doors.

The re-circulation door is servo controlled even though it only needs to be in one of two positions, one that closes the inside vent and routes outside air to the fan, and the other that closes off outside air and allows cabin air to be vented into the fan.

Then there are the 'blend' doors, one driven by a servo, and the second linked to the first, that controls the amount of air flow over the heater core.  These are controlled by the blue/red control knob on the dash.

Finally there are the Mode 1 and Mode 2 vent control doors.  Mode 1 door regulates air flow to either the dash vents or to defrost/floor.  When the Mode 1 door is directing air to defrost/floor the Mode 2 door chooses whether air goes to the defrost vents or out through the floor vents.  These doors are set in different positions to provide the various vent flow combinations available on the vent selector knob.

The hinges of these doors are plastic.  Periodically the ECM has to calibrate the servos and it does that by operating these doors through their full range of motion until they hit their hard stops.  This puts the doors under stress.  Eventually the plastic door hinges break. The cost of  removing the entire dash, steering column, and plenum (including draining the cooling system and evacuating the AC system) makes for a very expensive repair.

It was suspected that our re-circulation door had met this fate.  Probing within the cabin air intake verified the broken door and that it had fallen down into the fan intake.  The plastic grate over the vent was broken out and the door fished out.

The Re-Circulation Vent and Grate (under the wire bundle)

Re-Circ Door with Broken Hinge

There is a company that makes durable steel replacement doors but there is considerable disassembly required to pull the servo so the new door can be installed. What was needed was a quick fix to defer this project till after our return from Canada.

The broken door was used to close off the interior vent and secured with duct tape.  This blocks the cabin air intake but keeps exterior vent air from entering the cabin before being cooled or warmed. The outside air is ducted into the system as usual, but we don't have the option of re-circulating inside air until a replacement door can be installed.   We can live with it.  The good news is that strong vent airflow has been restored and we should be able to deal with any hot weather we may encounter during our upcoming trip.

Once again better living through duct tape.  During a recent commencement address the speaker, as part of their Star Wars inspired talk, asked how duct tape was like the 'Force'.  "It has a light side, and a dark side, and holds the universe together."