Dear Mudders,
My heat (or lack thereof) has been driving me to the point of wanting to sell my 100. For two years or so I have been battling extremely cold air through the floor vents, in some instances AC in winter, and moderate heat from the top vents. I finally fixed it through a succession of maneuvers. Hopefully this list will help somebody else in this same quandary.
1. Install new thermostat under the hood. While swapping heater Ts, back flush both the front and rear heater cores. This should remove the likelihood of “plumbing” being your issue(s). Rear heat worked like a charm after this step.
2. Replace the sensor that reads cabin heat and insure its vacuum line and electrical are hooked up correctly. This is right behind that tiny grill just under ignition. Photo showing grill and new part ($20 ish).
3. Remove blower fan on passenger side under glove box and make sure it is refuse free and clean running. Access at front footwell is easy, three fasteners.
4. Unconnect and reconnect the electrical connector on the small HVAC servo motor in the passenger floorboard area too. This was critical to my problem, either the connection was bad OR I rebooted this servo in the process. See connector in photo. I did this several times to clean up the connection.
5. Here is the sneaky one. Once the servo motor is now working (by giving differing commands at the dash) observe the metal shaft that is supposed to open and close a flap in the heater box near the servo. This shaft (photo) has a flat section on it for a reason, BUT mine was simply spinning in place. I pried the connection arm (carefully) down to make it seat on the flattened shaft, sprayed dry lube around where shaft entered the heater box, and voila The Heater Box flap began to open and close with the operation of the servo motor. This was an exciting moment!
5. Move your attentions to the dash area above the driver’s footwell. If you look up in there, other arms and flaps exist that need dry lube to work as well. Piece by piece, bit by bit, I managed to get all my flaps working again.
My heat appears to be working now to factory spec and it simply stays set to AUTO and a desired temp and delivers as designed. If you have similar issues, I hope some or all of these steps help you. I couldn’t find any of this on this forum, so decided to share. Happy Holidays.
My heat (or lack thereof) has been driving me to the point of wanting to sell my 100. For two years or so I have been battling extremely cold air through the floor vents, in some instances AC in winter, and moderate heat from the top vents. I finally fixed it through a succession of maneuvers. Hopefully this list will help somebody else in this same quandary.
1. Install new thermostat under the hood. While swapping heater Ts, back flush both the front and rear heater cores. This should remove the likelihood of “plumbing” being your issue(s). Rear heat worked like a charm after this step.
2. Replace the sensor that reads cabin heat and insure its vacuum line and electrical are hooked up correctly. This is right behind that tiny grill just under ignition. Photo showing grill and new part ($20 ish).
3. Remove blower fan on passenger side under glove box and make sure it is refuse free and clean running. Access at front footwell is easy, three fasteners.
4. Unconnect and reconnect the electrical connector on the small HVAC servo motor in the passenger floorboard area too. This was critical to my problem, either the connection was bad OR I rebooted this servo in the process. See connector in photo. I did this several times to clean up the connection.
5. Here is the sneaky one. Once the servo motor is now working (by giving differing commands at the dash) observe the metal shaft that is supposed to open and close a flap in the heater box near the servo. This shaft (photo) has a flat section on it for a reason, BUT mine was simply spinning in place. I pried the connection arm (carefully) down to make it seat on the flattened shaft, sprayed dry lube around where shaft entered the heater box, and voila The Heater Box flap began to open and close with the operation of the servo motor. This was an exciting moment!
5. Move your attentions to the dash area above the driver’s footwell. If you look up in there, other arms and flaps exist that need dry lube to work as well. Piece by piece, bit by bit, I managed to get all my flaps working again.
My heat appears to be working now to factory spec and it simply stays set to AUTO and a desired temp and delivers as designed. If you have similar issues, I hope some or all of these steps help you. I couldn’t find any of this on this forum, so decided to share. Happy Holidays.
