I have a 1991 Corvette that I removed the automatic A/C from. Every part was brand new from GM. The motor in the car is different with a carburetor, now. I'm making a street/ strip car. I would just leave the A/C off altogether, but it is just too hot & humid here in FL, so it has to stay. I have purchased the Manual A/C unit, & controller for it that is located under the dash on the right side of the gas pedal.

My question is this: Do I need to change the electronic blower fan controller with the one that has the resistor coils on it?

 

Yes and you'll need a Relay too and maybe another heater box since the Temp Door will now be activated by a Cable though you can probably modify yours to work. Best to work from a Factory Schematic for the electrical and I'm not sure how or what this will do to the Programming in the BCM, though maybe you've eliminated that too.

 

I have the entire heater box assembly already. I should have mentioned that earlier. Good point! I have a factory repair manual with the schematics for both HVAC types.

Are you talking about the blower relay that goes on top of the resistor, or a different relay?

 

Blower Relay - position it wherever it works for your application.

 

Manual AC on a 91 has 2 blower relays - see pages 8A-63 in the FSM for the wiring diagrams. The relays are mounted on the inside of the left fender well.

Why not just put all the auto AC parts back? Seems like a lot less work to me.

 

1) I'm very familiar with the 2 fender relays. They no longer go to my new dual fan setup. Thanks for the pages.

2) The auto A/C is setup to cutout when you press the gas pedal to the floor. It also cycles the door in the heater box back & forth upon start up. The problem is that the little door control motor is on top of the plastic heater box under the dash. The motor heater door rod holder (which is metal & connects to a metal rod) operates fine, but the plastic inner heater box it connects to keeps busting. I suppose a box could be reinforced or fabricated with some type of metal (like aluminum). I have to take nearly half of the dash apart to change that thing out. It's getting really old. Not to mention, I've had to change 2 of the controllers that are located way up under the driver's side dash. Those things are expensive! I'll be better off in the long run with manual A/C. It's much work, & probably is NOT the solution for most. I agree. I'm not so lazy that I can't move a **** on a Manual A/C head unit once it's connected, though.

3) It seems like I saw the heater box door control motor on a 1996 being located under the heater box. That would be a simple solution, because it could be changed without tearing half of the dash out again & again & again. However, I've removed much automatic stuff from this car. It's more race car than daily driver. As I mentioned earlier, It's just too hot & humid in FL, or I'd just take the whole A/C out.

Thanks for the replies.

 

OK. I was right. After some researching, I found out that there was a very common problem with the heater box door control motor tips breaking. With so much of the dash requiring disassembly, the motor was finally relocated to the bottom of the inner heater box on the 1994 to 1996 Corvettes. The 7v polarity for the motor just needs to be reversed for it to work on the 1991 Corvette. Also there was a change in some of the Heater & A/C Programmer Units with a capacitor to help prevent problems. The desired unit is Part Number: 16155285(6) depending on if it is for a ZR1 or not, but either 5 or 6 last digit should work. So, I guess I'll go this way, & see if I can finally enjoy this automatic A/C for a while without having to repair things that are hard to get at. At least the heater box door motor will be simple to replace, now !!!

 

what keeps breaking? maybe 91 was different then 90, but on my 90 my electric motor is directly connected to the blend-door. The blend-doors shaft comes through the box and into the blendoor motor. So it's a direct drive setup.

 

It is a direct drive setup, but the stops that connect to the motor break from the motor adjusting back & forth over time, & will throw trouble codes to the programmer, which is not the problem at all. The motor will usually spin from slipping. Gordon Killebrew warned GM about putting the motors on the top of the airbox in 1990 before he left GM in 1993. When GM finally switched the motors to the bottom in 1994, GM had to pay him back for his idea.

The main point is that one can save many headaches by buying a 1994 -1996 inner heater box, & relocating the motor to the bottom, & swapping 2 wires if the original motor ever goes out, or the drive slips causing nearly all of the dash on the passenger's side to be removed.


So, what keeps breaking? My heater door control motor, 2 programmers, 1 A/C head unit, & the actual inner heater box composite itself. It was a very expensive fix, since the motor was working. The broken airbox connection caused all of this. If the motor would have been located on the bottom, the problem could have been instantly seen, instead of hidden by so many dash parts. I contacted Gordon Killebrew personally, & he confirmed that GM refused to change the location of the motor until they started having numerous problems. That's why it was finally relocated to the bottom for quick access. The dash no longer has to be removed for the newer location. Gordon was the GM Corvette expert for the C4 Corvettes. I highly reccommend him for difficult C4 problems. He also has a Corvette training school.