So I had unhooked the battery....

After-which... I only had heat.
Found that my blend door stopped working.
Ordered a replacement gear on ebay and replaced the cracked gear inside my actuator. (seems to be common).
Got things back together; removed both RDO fuses to reset the actuator a few different times....
It just keeps cycling back and forth; hot, cold, hot, cold.....

In the process of trying to figure this out; I broke the plastic tab off the lever that the VAC Unit is connected to in the photo:
(photo looking inside glove-box area)


What does this VAC unit do ? All my HVAC functions still appear to be working.

I cracked the HVAC box near this lever that is broke; probably going to pull the whole dash now so I can get adhesive in there and repair it.

1. What is the fix for the blend door that keeps going hot cold.... ?
2. What is the VAC unit for in the photo ?
3. Is there a "how to" for removing the dash ?

Thanks.

 

Ok, I think I have all the data for removing the dash.

Still curious to 1 and 2.

Thanks.

 

Ok.... kinda disappointed that I did not get a single comment on this thread. With that being said....
If your blend door continuously cycles hot/cold over and over; I have the answer and how to fix it. Very easy fix and I'm sure many have given up and just spent the $100+ on a new actuator. I have searched all over the web and all I find is "remove the RDO fuse, etc...." or "use jumper wires on the actuator..." If you have disassembled the actuator or powered it on while removed from the blend door; it is over-driven or out-of-time. Removing the RDO fuse will not correct this. It needs manually re-timed.

Post a reply if you want help.

 

I actually do not know for certain what the vac actuator does, but I thought it was for the Fresh or Re-circulate function. I think this is only used for the MAX A/C and normal A/C...but again not for certain.

I had a similar problem on a '95 Corvette that I once had, where the blend door got out of synch or timing with the controller. I had to have the cover off of the actuator with the electrical connector attached and then move the temp setting **** and watch the gear position...remove gear, reset gear, try again. Took several adjustments, but once I got it in the the correct position for full hot and full cool....it is still working fine.

Did you have to do something like this?

 

I took the electric actuator all the way apart, had a ohm meter on the potentiometer and realized it was a single turn 8k pot. At 8k it would jump back to zero; which is what throws the computer off. I centered the pot at 4k "middle" and then centered the output gear. DO NOT power the actuator yet, put it back on the HVAC box, then test. The actuator can travel something like 90 degrees or more, the door on the HVAC box only moves half that. I have some photos I can use to elaborate if anybody needs help.

 

Hey, i have exactly the same problem. I had unhooked the battery and now it works only at full hot or full cold.

Some photos would be great!!!

 

So you can still get it to blow cold AND hot ?

Open the glove box all the way. The actuator is labeled "problem" in the photo above.
CAREFULLY remove the vacuum unit in front of it, then use a 7/32 socket to remove the (2) screws on the actuator. Get on ebay and search for the blend door actuator gear. Disassemble the actuator and replace the gear.
The KEY here is to NOT move the little blue gear, and put everything back in at the exact same clocking. Do not plug in the harness or restart the vehicle until the actuator is back in the truck.

 

Yes, there are just two positions now, full cold and full hot.

I replaced the blend door actuator last year and it worked great until i unhooked the battery.

I will disassemble the actuator and look if there is a gear broken.

How did you adjust the pot?

 

Does your truck have the automatic climate controls ?


Adjusting the pot requires a multi-meter.

 

Yes, automatic climate control.