BIG EASY BOB

Tried to use the heater last nite in my 95 coupe and it only blew warm air...Took out the blower resistor to see inside the heater box and the blend door is pulsing in the middle,,Is there any way to shut it so only hot air comes thru and then be able to open it next summer. Thanks in Advance for any Help, Bob

mike c4

try battery disconnect

HAD2HAV2

BIG EASY BOB, I think your AC/ Heater programmer is on the fritz.

pcolt94

This is the first step and will reset the control head and programmer.

The programmer is the primary driver for the blend door which activates the motor.

Make sure it is not wet up in the passenger compartment where your feet would be but higher. If the evaporator drain was slow or plugged, it can back up into the housing and get the blend motor wet. The feedback circuits then don’t work right.

Programmers don’t go bad much but when they do they usually cause the control head not to light or work correctly or lock up. I have not seen or heard of one that pulses the blend door. There are 4 capacitors that usually get changed that corrects most of common problems .

HAD2HAV2

BEB, if your blend door motor doesn't move the door when you move the temp. up or down (never heard of pulsing) then you may have a programmer problem. Have a 88 with C68 and have been there.

CebuRyda

I just went through this last weekend. In my case I had multiple problems. I had my C68 controller display "--.--" at times instead of real values. I tried the clean the edge connector with an erase approach and that worked for awhile. My problem the display would go black even though the I can hear the fan increase or decrease by pushing the up/down arrows. I ended up taking it apart again but this time soldering wire between the connections. I removed the edge connector (there is a great write up on the net, that's where I got my information from)

My 2nd issue was a vacuum leak. I thought maybe there wasn't enough vacuum getting to the under dash programmer module. I found a hose that came from a "T" connector that was supposed to connect to the cruise control module. It has broken off about an inch from the nipple. The connection is underside so unless you know what your looking for it's not that easy to find.

My 3rd issue was the programmer. In a nutshell I had cold and fractured solder joints in the known resistor failure areas. Knowing what I know now it will be a heck of a lot easier the next time I do it. I plan on bi-rating the wattage value of the stock resistors later. One advise is to just remove the drivers seat. I'm about 6' 250 pounds and I barely had enough room stuff my big head under the dash. I'd also remove the PC board without disconnecting the vacuum hoses connected outside the case and disconnect the hoses inside the case. They are much easier to work with and if you have a bad PC board you may have dodged a bullet messing around with the outside hose connections.

I included some photos to give you an idea what it took in getting my heater running. I had the same issue you described. It's not that bad of a project just be patient and keep track of how you took things apart. I took a lot of photos so I could refer back to them later, I'm old so I can't remember much

Cheers and ride safe!

pcolt94

You're doing some good work there. The 88 is quite different than the 94 and 95. There is a write up on those resistors you talk about for years. Doesn’t seem like you need the post anymore.

BIG EASY
Here is my thread on the capacitors and some info from others, just in case…….for the future.

https://www.corvetteforum.com/forums...-repaired.html

CebuRyda

I believe I read your thread during my searches. Seeing how you and others tackled projects motivates me to do the same. Thank you for the links I have it bookmarked.

Cheers and ride safe!

HAD2HAV2

[QUOTE=CebuRyda;1591046124]I just went through this last weekend. In my case I had multiple problems. I had my C68 controller display "--.--" at times instead of real values. I tried the clean the edge connector with an erase approach and that worked for awhile. My problem the display would go black even though the I can hear the fan increase or decrease by pushing the up/down arrows. I ended up taking it apart again but this time soldering wire between the connections. I removed the edge connector (there is a great write up on the net, that's where I got my information from)

My 2nd issue was a vacuum leak. I thought maybe there wasn't enough vacuum getting to the under dash programmer module. I found a hose that came from a "T" connector that was supposed to connect to the cruise control module. It has broken off about an inch from the nipple. The connection is underside so unless you know what your looking for it's not that easy to find.

My 3rd issue was the programmer. In a nutshell I had cold and fractured solder joints in the known resistor failure areas. Knowing what I know now it will be a heck of a lot easier the next time I do it. I plan on bi-rating the wattage value of the stock resistors later. One advise is to just remove the drivers seat. I'm about 6' 250 pounds and I barely had enough room stuff my big head under the dash. I'd also remove the PC board without disconnecting the vacuum hoses connected outside the case and disconnect the hoses inside the case. They are much easier to work with and if you have a bad PC board you may have dodged a bullet messing around with the outside hose connections.

I included some photos to give you an idea what it took in getting my heater running. I had the same issue you described. It's not that bad of a project just be patient and keep track of how you took things apart. I took a lot of photos so I could refer back to them later, I'm old so I can't remember much

Cheers and ride safe!


























Multiple problems suck. The plastic clip that attaches to at air blend door motor to the rod that controls the air flow broke. I fixed that but during the process of testing my fix the AC programmer went bad.

C4 Grey Beard

In my 86 the air blend door was pulsing because of a striped gear. The motor was running but the door was just vibrating.