87 C68 Control Head Problem
Thread Starter
Pro
Joined: Oct 2003
Posts: 506
Likes: 12
From: Savannah GA
87 C68 Control Head Problem
I'm freezing on the way to work..... So I know the heater door is closed all the way. AC, defroster works reasonably, not a programmer problem.
I get the blinking temp on start.
Diagnostic mode 8 shows code 01 for improper feedback signal.
At the heater door motor I don't get a change in voltage polarity when moving the temp from 60 to 90.
FSM says replace the controll head. I'm not intrested in $350 for a rebuilt one.
Can someone give me some hints? I can feel up there, the rod is in place. I don't want to break some impossible to replace 20+ year old plasitc.
I read the system moves the motor back and forth to determine it's position on start. Could something be stuck?
I've been looking for a circuit diagram for the control head. If I can find one I can fix it.
I've had the controller out and I don't think the warped white connector on the face is causing the problem.
If nothing else I'm going to try pull the motor out to get the door open.
It's been cold even down here in Georgia!
Thanks for any help.
JS
I get the blinking temp on start.
Diagnostic mode 8 shows code 01 for improper feedback signal.
At the heater door motor I don't get a change in voltage polarity when moving the temp from 60 to 90.
FSM says replace the controll head. I'm not intrested in $350 for a rebuilt one.
Can someone give me some hints? I can feel up there, the rod is in place. I don't want to break some impossible to replace 20+ year old plasitc.
I read the system moves the motor back and forth to determine it's position on start. Could something be stuck?
I've been looking for a circuit diagram for the control head. If I can find one I can fix it.
I've had the controller out and I don't think the warped white connector on the face is causing the problem.
If nothing else I'm going to try pull the motor out to get the door open.
It's been cold even down here in Georgia!
Thanks for any help.
JS
Racer
Joined: Jun 2006
Posts: 408
Likes: 0
From: Elkton MD
No heat
Are you sure that there's hot water flowing thru the heater core? Earlier years had a flow control valve. Or the core may be plugged up.
To flush the core, take the hoses loose at the block. The core nipples are fragile and pull out of the core easily. If you must remove the hoses from the core nipples, cut the hoses off with a sharp cutter.
Hope this helps.
To flush the core, take the hoses loose at the block. The core nipples are fragile and pull out of the core easily. If you must remove the hoses from the core nipples, cut the hoses off with a sharp cutter.
Hope this helps.
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
Thread Starter
Pro
Joined: Oct 2003
Posts: 506
Likes: 12
From: Savannah GA
WOW, one day I'll learn to read.
The control for the heater motor DOES COME from the programmer up above the gas pedal.
Both heater core pipes are hot. I pulled the motor out and the door isn't stuck and the motor will move with voltage on pins C & D. I ran it some and heat will come in the passenger compartment. It's something how well the heater core is sealed off!
Now I can see if I can convince the crappy programmer to work. I found the diagrams for it.
JS
The control for the heater motor DOES COME from the programmer up above the gas pedal.
Both heater core pipes are hot. I pulled the motor out and the door isn't stuck and the motor will move with voltage on pins C & D. I ran it some and heat will come in the passenger compartment. It's something how well the heater core is sealed off!
Now I can see if I can convince the crappy programmer to work. I found the diagrams for it.
JS
Intermediate
Joined: Oct 2009
Posts: 26
Likes: 1
From: Madison TN
I agree. It is the programmer. I am having the same problems. I found a used one for about $100. I'm waiting for it to arrive and I hope it resolves the problem. Everything else works fine. It just will not cycle back to heat when activated. We'll see.
Thread Starter
Pro
Joined: Oct 2003
Posts: 506
Likes: 12
From: Savannah GA
Here is some more info on C68 heat and AC problems.
For issues with the programmer take a look here:
http://www.batee.com/corvette/acrepa...oard/c68.shtml
My issue was with heat. The heater door motor wouldn't move. Before you take the motor out do the FSM table A4 test.(I think that's the one) Look for 12v and 0v on the motor windings with the temp at 60 and 90. When the temp is changed from one end to the other the voltage changes leads and the motor opens and closes the door.
The problem I found was the circuit board had deterioated on the 140ohm resistor leads. The foil runs are so thin 20+years wore them out. I tried to add more solder but the eyelets around the leads just fell off. I striped out some CATV wire and bridged the burned up runs. It didn't look fantastic but it works. I also added another lead over to the 12v feed to the relay coils.
The 140ohm resistors looked pretty shabby but they were OK resistance wise. I belive they are to limit current through the heater door motor windings.
Many problems are rooted in worn out runs on the programmer board around those two big resistors. The 12v source runs across the top of them and may cause problems with the relays to.
JS
For issues with the programmer take a look here:
http://www.batee.com/corvette/acrepa...oard/c68.shtml
My issue was with heat. The heater door motor wouldn't move. Before you take the motor out do the FSM table A4 test.(I think that's the one) Look for 12v and 0v on the motor windings with the temp at 60 and 90. When the temp is changed from one end to the other the voltage changes leads and the motor opens and closes the door.
The problem I found was the circuit board had deterioated on the 140ohm resistor leads. The foil runs are so thin 20+years wore them out. I tried to add more solder but the eyelets around the leads just fell off. I striped out some CATV wire and bridged the burned up runs. It didn't look fantastic but it works. I also added another lead over to the 12v feed to the relay coils.
The 140ohm resistors looked pretty shabby but they were OK resistance wise. I belive they are to limit current through the heater door motor windings.
Many problems are rooted in worn out runs on the programmer board around those two big resistors. The 12v source runs across the top of them and may cause problems with the relays to.
JS
