treedweller

Just read lots of noise threads, but can't find one like mine. I have an '02 2500. I just started hearing this noise under my dash. It starts when I turn on the key, with or without the engine being on. It kinda goes buzzzzz--clk-clk-clk-click--click--click. Lasts about 8-15 seconds, stops 8-15 seconds, cycles like that as long as the key is on. I located it inside the plastic housing near the blower motor and can feel vibration and heat coming from the rectangular area circled here:



I don't know what's in there, so I don't know how to look it up in my repair manual. Anyone know what's going on? So far, I haven't noticed any changes in how anything else works.

TIA,
k

torquefan

That is right where your heater core lives. The thing right beside your circle is the blend door actuator. Sounds like it is getting noisy, or something has fallen into the blend door's path and is restricting its movement. Does your heater temperature cycle from hot to cold ok when you switch it?

treedweller

Thanks for the reply. I haven't noticed any problems with heat/AC. This happens when all climate controls are off. Turning on heat/AC works fine.

nickg

just for fun unplug the electric connector on the blend door motor(the one in your picture) to see if your noise stops

treedweller

Okay, you guys are right. Unplugging the motor stops the noise.

So will replacing the motor fix the problem? Or do I need to find a bad switch that isn't turning off somewhere? Cause the heater is definitely off when I hear the noise.

Also, I'm not seeing that part name at Geno's Garage or RockAuto. I did see "ACTUATOR,HTD INT AIR VLV THERMAL" which looks wrong.

Do I need to go to the dealer for this motor?

torquefan

It may do a calibration sweep with every key cycle, so the operation at key-on is probably normal.

To diagnose the noise, I'd remove the actuator from the heater assembly, then move the blend door manually from open to closed and see if it binds or makes noise.

Additionally, with the key on, and actuator removed but still plugged in, you can sweep the temperature **** from hot to cold and back, and watch the actuator move. Look for binding and noise or jerkiness while it isn't attached to the blend door. Pay attention to what position the actuator's shaft is in before doing this, so you can get it back close to its original position to make re-assembly easier.

torquefan

And yes, I would think the actuator is a dealer-only item.

JoeCanuck

Mine was doing the same thing. The problem was not with the blend door actuator but with the connector between the actuator and the blend door. It's a crappy piece of plastic and it can break.

When the control is at full cold or full hot, the motor never powers down. What is supposed to stop it is the blend door bottoming out. The motor is still trying to turn. This provides a constant force against the blend door limits to prevent leaks.

The motor will only hold position when the control is between the 3 and 9 o'clock positions. If the blend door doesn't stop it, it will spin forever at full cold and full hot, with the key on.

Here's a test; put the control straight up, the 12 o'clock position. It will probably grumble for a few seconds then stop. The only time the motor stops on its own is between 3 and 9.

Pull off the motor, (2 phillips screws), and pull straight down. The connector may come off with the motor but probably not. It also comes straight off by pulling down. It may take a some force. Mine was reluctant to come off because it had cracked and was spun on the shaft so it was a bit jammed.

It seems this is a fairly common failure item. You can even find overpriced replacement connectors on ebay. I repaired mine with a metal sleeve and epoxy.

Good luck.

treedweller

I knew this was the place to solve this problem. Thanks to all for the help. I'll get on that test after I finish the newspaper.

k

treedweller

Okay, here's what I found.

First, that #@&!!*#@ bolt at the back of the motor housing is the biggest pain to reach I've seen in a long time. I got it off, but god knows how I'll ever get it back in.

Anyway, dropping the motor, I can turn on the key and watch the lug that moves the door rotate. It will keep going endlessly unless I turn the temp **** to 12 o'clock, as JoeC said. I can turn the pin on the flapper with my fingers and feel a hard stop when it reaches the end of its range in both directions. If I use a screwdriver, I can keep turning it, but it isn't easy. When I mount the motor back on, it does manage to keep turning beyond where I assume it has moved the flapper all the way to either side.

So I took the housing off the motor and looked. Everything seems to look like it should. Nylon gears, but no visible damage to the teeth. I can't tell how the motor knows to turn off. I tried holding the lug to mimic a hard stop but couldn't grip it tight enough to stop it.

So, is it in the module? or do I have to get to the flapper to reinforce the connection there?

If it's the latter, how do I get in there? It looks to me like I will have to pull the blower motor and all the rest of that plastic housing. Any advice before I start that? It look like just a couple of plugs to pull and then a few screws to drop it all, but I'd like to avoid any nasty surprises.

JoeCanuck

It's probably not the module itself. My problem was with the plastic connector between the actuator and the blend door. If you have the actuator off, the connector is probably still stuck on the blend door shaft.

The only task of the connector is to join the actuator shaft to the blend door shaft. If it's cracked, as mine was, the motor will keep spinning endlessly when the heat control is at the extremes.

You can test the motor by plugging it in, without it being mounted. Full cold; it will spin in one direction. Full hot; it will spin in the other. Between 9 and 3 o'clock positions; it will stop and will move in direct relation to the heat control ****.

YOU DO NOT HAVE TO TAKE APART THE DASH...!

It might take a bit of a tug but the connector will come off. I bet it's cracked.

I found taking off the actuator a pain until I got a 90 degree screwdriver, pulling back the carpet and cutting away some of the thick insulation below the carpet. I also took the extra time and removed the passenger seat. It lets you lie on your back in relative comfort. Well worth the 5 or so minutes work.

I also took apart the actuator and found nothing wrong. It was a fluke that I tried the actuator by plugging it in and watching the action.

treedweller

Finally got back to this today, and JoeCanuck called it. I pulled off the plastic piece (had to use pliers) and it was cracked. I reinforced it with a twist of electric fence wire instead of a metal sleeve, but otherwise followed Joe's path to the letter, including cutting away some of the thick rubber below the module so I could get my 90* screwdriver in there. Inelegant, perhaps, but everything seems to be working again.

Thanks, Joe, for helping me avoid some major headaches working this out.

JoeCanuck

No worries...the problem plagued me for some time before I finally got it solved. Glad to help.