strange clicking noise in heater system

[steve-r]

started today. sounds like a door or vent popping or clicking open/closed inside the heater in the cab...about once per second. changes when i push MAX or sometimes when i change fan speed. it will "pop" for 15-30 seconds then stop for no reason. then will start up again. will also "pop" for 15 seconds after I shut off the key. lastly, will stop when i pull the heater/AC fuse. i've been searching the forum but no direct hits... there must be an actuator in there that opens or closes a vent door ...maybe it changes air flow from defrost to floor and back....anyone had this? any suggestions to diagnose or parts to replace? major overhaul of heater/AC system or quick parts exchange.....your thoughts?

[eracers999]

Steve;

I call em Door motors, on the sides of the heater a/c box inside the truck, you will notice these little flat black square boxes with wires running to them. They respond to a reference pulse from you heater control. They arent to bad to change out. Little pricey from GM, cheap at a bone yard. I believe you will need a 9/32 socket. Good luck.

Kent

[fastcat800]

Thanks Kent. I have the same problem too. Every time I start the truck it makes noise for about 30 seconds and does the same thing when I turn it off. It is the fresh air / recirculation door on mine that is making the noise.

[steve-r]

Kent, thx. I called my local GM sevice guy today. He said it was the Recirculating air actuator. there's another one ( actuator ) in there for temperature control. $102 Cdn for the Recirc actuator, and $250-$650 to install it. some are apparently easy to swap, and others require the dash removed. why i don't know but that's what he said. i'll try the boneyard and have a go at it myself before i toss away $650.

[diesel65]

When I had 94's in the fleet, it was always the recirculation door motor that went bad. It was the hardest motor to change. GM says to pull the dash but I was able to do it with a 5.5mm 1/4 drive flex-socket from Snap-On and a 1/4 inch air rachet, with alot of cursing thrown in.
The bottom screw is easy to remove, the upper screw you can't see and have to do it by feel and guessing where to aim the socket.

[charliepeterson]

diesel65 is right about the recirc motor. Another thing to look at is the door pins them self. The pins are in plastic bushings which wear out and can fall down and bind up. If this is the case the heater box really needs to come out now. This is why the job is so expensive, the dash gets layed down on the front seat. The job is all labor for about $2.00 worth of parts.

[steve-r]

how do you spell frustration !!! arrgh!
i got it out without taking out the dash, but what a pain. a few contortions and some torque on my back that i'll feel tomorrow. that back screw near the firewall was almost impossible. at least the clicking noise has stopped. since I never use Re-circ in this climate, I think I'll run without it and see if I notice any problems. i did notice that the re-circ vent now pulls open slightly (1/4 inch) from the fan drawing air as its just on a light spring, so the airflow actually increased slightly.

[fastcat800]

Can you unplug the wires without removing the motor? That would seem like an easy fix if you can.

[steve-r]

you could reach up in there and cut the wires, but no way that I can see to disconnect the wire plug without removing the actuator first. you just can't get your hand up there, nor can you see the plug, its on the top.

thanks all for your comments and suggestions. once again this forum has saved me money. thanks !!

[fastcat800]

I fixed mine for now. I put a 1" long piece of 5/16" gas line to hold the door open about 1/2" and it doesn't make noise. I noticed if I held it open slightly by hand it stoped thumping. It will be OK until I hit Max on the AC and it closes the door and piece of hose falls out.

[portabull]

i betcha this is the same thing i called my
"puppy dog" noise. it seemed the frequency
was about the same as a dog furiously scratching
his ear with his hind leg.

[Scooby]

Has anyone pulled the dash out?? I was wondering
how it comes out, and where you start !!