a/c-heater blend door or servo motor problems
 

First time needed to use heater in my 89 convertible and found no heat through flloor vent. Ran temperature control to the max and still cold air. Believe problem lies somewhere in the above. Definitely can't hear any opening/closing of blend door. Don't want to pull the dash(unless necessary). Need to check all vacumn lines for leaks and possibyl servo motor. Haynes shop manual no help. Any diagrams or info, even "the spoken word" would help. Thanks.

Me too.... and a 89' Changed Thermo to 180 for winter. Still no heat

Well have done a lot of reading and Heater core not blocked so going to check the operation of the vent door. and then where to buy the servo blend motor? and how much?

Thanks Guys for all the info!

The motor is around $20 at the dealer. I believe mine is a cracked heater door gear so there is a good chance your motor is fine.

Here is a post with a lot of info. Heater Door Thread. I still haven't fixed mine and it's been almost two years now with no heat. Thankfully I live in Florida. Hope to be taking it in soon to have my guy check it out to confirm it's the heater door.

Good luck...

The '89 often ends up with a plugged up core due to exhaust in the coolant which leads to galvanic corrosion. Once it's plugged up, coolant flows over the top of the core but not through it (and if it didn't something would blow apart somewhere). If your coolant is fresh and allready looks like crap, you may have other issues. Otherwise, blend door problems are verified by removing the Blower Motor Module (electronic air) or Resistor Pod (manual air) from the left side of the Evaporator case. You can then observe what the door does while someone operates the controls. If the door doesn't move, electronic air moves the door with a motor that's connected to the door linkage with a plastic clip (manual is simply connected to a cable - later years are gear driven). That clip may have broken, but first, verify that the motor runs. You can either jumper it to battery voltage or simply disconnecting and reconnecting the battery should cause the motor to move through a complete cycle and you should be able to hear it run. If it doesn't, you should jumper it to a power and ground and if it still doesn't run, you know that it needs to be replaced. If it does run while jumpered, the problem is likely in the Programmer - a postcard size device above and to the right of the accelerator. Some take it apart and resolder the board, others buy a replacement.

Mine was the programmer on the 89, lots of fun to change:thumbs:

Well, replaced the Electronic control, my display was out anyways.. Still did not fix it.. Checked the core with the air hose.. Not plugged.. Removed the Module and moved the door to close.. It had resistence on it.. So Put a piece of Cardboard down there to keep in in the "medium" blend setting until I can get time to pull the hush panel and check the arm or gear.. The door would move back to cool but not to hot? So for now I have some Poor man's heat!

And thanks for the replys

But for now been chasing some crazy miss firing! New plugs... Fairly new wires MSD... new cap.. New Module, button etc... All I did was change the Plugs to the Bosh 4's and ran great! But then sprayed off the intake with carb cleaner (checking for vacuum leaks) still ran great... Got in the car a hour later.. Missing... Sprayed it off with water made it worse.. Drove it to a dinner party..@ 30 drive.. Next day still missing... Changed out each plug with a new one and cranked it up each time.. bypassed the MSD.. still missing... I pulled the cap off and sanded the contacts lightly.. Fixed it... Drove it to visit my Handicaped sister... set @ 1 hour.. Miss is back... Also did the night time test with some purple power... slight sparking but not the cause... put a little dielectric greese on all conections, still missing ... Pulled the cap back off because it fixed the problem last time and did nothing to it...fixed it again? could the coil be bad causing it to miss under load and be e-r-r-a-d-d-i-c !!!!!
Plugged the MSD back up and for now... running Great.. But do not like not know what I did to "fix" it.

Drove the car today... Missed a little after warm up and then went away...???????

going to change out the new cap... And then... back to the heat.

Hope to be taking mine in next week to find out about my heater door situation. Have a new motor and new door housing already just in case...

Hello out there! Does anyone know where to get a blend door motor for a 1991 vette? HELP!

Blend door motor
 

Try Coastal Corvette out of florida. They had one for my 89.

Aks for John. 321-269-4995

Check the date on this thread. He's probably found one by now.

i did everything to my `87 and i still get almost no heat, up here in central PA and it is cold here. first problem is getting engine temp up. with new thermo it barely reaches 160, if it it sits still in garage it will go to 195 and thermo opens. i think recirculting motor may be bad because cold air keeps coming in. so first prob, why can`t it stay hot when driving? in summer with A/C on it never overheats, runs to 190/210.

You really should start a new thread, but…

Do you have the C60 manual HVAC or the C68 digital HVAC system? The C60 has a slider to control the temperature and the digital one has a temperature display.

One possibility is that the vacuum check valve next to the distributor is bad and no vacuum is getting into the cockpit to move the HVAC door actuators.

Is the car running hot or overheating??