Repairing your Electric Heat/AC Actuator

Copied with permission from John D2

Repairing your Actuator....
After diagnosing the problem down to a failed actuator, I decided to see if I could repair it. This is what I found:

The cover is held on by 4 screws, remove them.
- Lift the cover straight off – hopefully leaving the gears on the shafts in the lower ½.
- Make a reference mark on the blue gear with a Sharpie marker… some kind of mark, straight up, 3 o-clock, something to reference the position of the gear.


Inspection:
1) Look for stripped gear teeth. Inspect the largest (top) gear carefully! Mine had a hairline crack from the hub all the way through to the teeth. (This crack was allowing the gear to just spin on the shaft, not turning it… thus no hot air!
2) Look for evidence that the 8-pin IC chip has blown. Mine had a small spot on the circuit board where all the smoke got let out. (Probably from overheating because the motor-drive was constantly “on” with the shaft slippage)


Repairs:
The IC chip was made by Motorola. Numbers on it were: KLG9531 & 0372DP1. These numbers cross-over to a NTE1854M, which is readily available from an electronics supply house. I ordered one from Newark Electronics . Cost $4.19 plus S&H.
- A few days later my new IC arrived, and I de-soldered the old one from the board, then installed the new IC (pay attention to the reference mark/dot on the chip).
- While the soldering iron was still hot, I also carefully “heat-fused” the crack in the main gear – melting the two sides together.

Testing time!
- I reassembled the unit (taking a bit of time to “redistribute” the gear grease back on the gears), checking my blue gear reference mark, and took it out to the car. Started it up and let it get warm. Shut the car off.
- Don’t remount the actuator! Just plug it in for this test.
- Restart the car and cycle the temperature adjustments from full COLD to full HOT. Watch the actuator. It should spin the top/main gear about 60 degrees “lock to lock”. If it does…. SUCCESS! You’ve rebuilt the unit for $4 bucks. If not… you’re probably off to the yard or dealer.

If your repair is successful, re-install the actuator on the shaft ( I used a few dots of epoxy smeared around the inside of the gear so it would fill the voids/splines of the shaft & gear – no slippage), and bolt it down. But, you’re not done yet… it needs to be calibrated!

- Shut off the car, and pull I/P fuse #33 (10A) for at least one minute.
- Reinstall the fuse, and start the car/turn ign. to “run”. This should re-calibrate the unit.

If you still don’t have heat, or the shaft doesn’t turn:
- The splines in the gear are probably shot
- The gear has re-cracked.
- The motor is shot, (It’ll spin “no load”, but not enough torque to move the workings).
You need a new actuator.
Hope this helps!