Posting my troubleshooting experience on a heater issue on a 1994 GCC Spec LC 80. I was missing a short connector on the wire harness behind the gauge cluster. The story/troubleshooting below. This one may be new to IH8MUD and hope it helps in the future.
History: My heater never worked when I purchased and exported it from the Middle East. I assumed the heater was never needed by PO and I probably had a dead mix servo motor, the gears worn, or just full of Bahrain dust. I never seen it move when I adjusted the hot/cold temp select so that's where I started.
For those that don't know: The Servo mix motor is on top of the heater mix box--it also moves the cable to open the coolant valve in the engine bay allowing fluid to flow into the heater core.
I started my troubleshooting at the servo motor. I checked the plastic gears, grease, voltage and even tested movement with a 9V battery. All Good.
With motor testing good, I moved T/S efforts to the loss of voltage. I started on the back side of the AC heater control unit (button box). Moving the selector from Cold to Hot, I saw a fluctuation of about 2 to 5 volts. 5V being max on heater setting set to max. I found the G-W wire and saw 5Vs leaving the back of the control unit (big blue pin harness).
After the Temperature selector the 5V signal needs to get to the AC System amplifier to give it enough "juice" to move the motor. But before it reaches the amplifier it goes through an A16 short connector. I knew I needed to find this because at the amplifier I did not see the 5Vs. ---It got lost and never made it to the W-G wire. And Y-G (amplified voltage never made it to the motor). Also, somewhere the G-W wire now became W-G.
I searched everything online for a short connector with no luck. In frustration, I was about to unravel the entire wire harness and chase this G-W wire and as I grabbed the wire harness I saw two plastic connectors with nothing attached to them. The plastic connector (mine being A16) is behind the wire harness and is taped snuggly behind the area where our gauge cluster sits. If you weren't looking for it, you would probably never even know it existed.
Below--photo on the left-- is the plug where a small plastic short connector is supposed to sit (an example from a 97 is on the right photo), it simply connects pins on a plug and mine was missing. Think of it as plastic jumper. I knew I would probably never find the exact part in the time needed to get my LC back in order, so I decided to make my own out of paperclips to connect the circuit to see if this was my fault. With the pins shorted per the schematics (careful not to short or touch each other), I saw my motor moving! I did a cleaner wire connection job with wire clamps and now the heater works with a servo mix motor that moves air from hot/cold boxes and moves the cable in the engine bay when heater temp is selected.
Hope this helps for future reference. I don't know why my short connector was missing or if I bypassed something that I wasn't supposed to (experts feel free to jump in). All I know I was missing the signal, found it, and connected it as the schematic says. Also, the wife is happy with a heater that works.
4 weeks in using the heater and no faults, shorts or fires---Maybe I did something right.
Thanks.
History: My heater never worked when I purchased and exported it from the Middle East. I assumed the heater was never needed by PO and I probably had a dead mix servo motor, the gears worn, or just full of Bahrain dust. I never seen it move when I adjusted the hot/cold temp select so that's where I started.
For those that don't know: The Servo mix motor is on top of the heater mix box--it also moves the cable to open the coolant valve in the engine bay allowing fluid to flow into the heater core.
I started my troubleshooting at the servo motor. I checked the plastic gears, grease, voltage and even tested movement with a 9V battery. All Good.
With motor testing good, I moved T/S efforts to the loss of voltage. I started on the back side of the AC heater control unit (button box). Moving the selector from Cold to Hot, I saw a fluctuation of about 2 to 5 volts. 5V being max on heater setting set to max. I found the G-W wire and saw 5Vs leaving the back of the control unit (big blue pin harness).
After the Temperature selector the 5V signal needs to get to the AC System amplifier to give it enough "juice" to move the motor. But before it reaches the amplifier it goes through an A16 short connector. I knew I needed to find this because at the amplifier I did not see the 5Vs. ---It got lost and never made it to the W-G wire. And Y-G (amplified voltage never made it to the motor). Also, somewhere the G-W wire now became W-G.
I searched everything online for a short connector with no luck. In frustration, I was about to unravel the entire wire harness and chase this G-W wire and as I grabbed the wire harness I saw two plastic connectors with nothing attached to them. The plastic connector (mine being A16) is behind the wire harness and is taped snuggly behind the area where our gauge cluster sits. If you weren't looking for it, you would probably never even know it existed.
Below--photo on the left-- is the plug where a small plastic short connector is supposed to sit (an example from a 97 is on the right photo), it simply connects pins on a plug and mine was missing. Think of it as plastic jumper. I knew I would probably never find the exact part in the time needed to get my LC back in order, so I decided to make my own out of paperclips to connect the circuit to see if this was my fault. With the pins shorted per the schematics (careful not to short or touch each other), I saw my motor moving! I did a cleaner wire connection job with wire clamps and now the heater works with a servo mix motor that moves air from hot/cold boxes and moves the cable in the engine bay when heater temp is selected.
Hope this helps for future reference. I don't know why my short connector was missing or if I bypassed something that I wasn't supposed to (experts feel free to jump in). All I know I was missing the signal, found it, and connected it as the schematic says. Also, the wife is happy with a heater that works.
4 weeks in using the heater and no faults, shorts or fires---Maybe I did something right.
Thanks.
