Location of the vacuum hose

If you go straight back from the middle of the engine compartment, under the PCM, on the firewall you will see a black oblong plastic canister with a vacuum line going in one end. The vacuum line has a tee, one end goes to the brake booster the other goes to the firewall between the A/C hoses and to the A/C controls. Disconect the vacuum line right before it turns into a black plastic line. Plug the canister side of the vacuum line and leave the firewall side unpluged. A vacuum switch could be used to acomplish a switch to disconect the vacuum, lets make sure first that the system will defrost with out the A/C on.

 

You can also wire a switch into the controls. I'll try to find my post, but that's what I've done, and it's worked well.

 

Here's the original thread.

https://www.greenhybrid.com/discuss/...-hybrid-13755/

 

Ah yes... I remember those posts. Very detailed and nice setup. Especially the LED for knowing when the A/C comes on of its own accord.

I'm just ruminating in this case if its effective to close a valve on the vacuum system that would open the top vents on the dash. That might in the end be simpler (less elegant to be sure). Then you'd just put the system in one of the heating modes and pop the switch... it would close the valve to the HVAC vacuum system and as Mark says the default would open up the defroster vents. The A/C logic would be completely unmodified so the system could do whatever it wanted for the battery, the only difference is where the heat comes out.

 

And allot easier to do.

 

While it's true that what you are describing is easier than what I did, a simplified version of what I did would easily work. As I recall, there are two wires that control the AC. All you need to do is hook those to 12v when you want AC, and disconnect them when you don't. A simple switch would have worked.

To me, that seems easier than mucking with the vacuum system. But it had better since I'm an electrical engineer!

 

Does that modification disable the A/C so that the battery cannot request cooling? I'm just more nervous of messing with the A/C controls rather than just redirecting the air is all. If I redirect where the air comes out during a non A/C mode I've done nothing to the A/C control system, so the battery can do whatever it needs. I'm an EE as well.... I just haven't looked deeply into this system to know what the lines control.

 

As Mark E Mark (I mean Smith) pointed out in the other (resurrected) thread, the only thing I muck with is the dashboard input, not the ability of the car to control the AC as it sees fit. It would be equivalent to selecting vent on your face. This mode doesn't request AC. I simply expanded all the modes to not request AC. And I made my AC request a separate input.

I believe the other post provides enough info to show you which control wires would need to be cut and hacked, but if I'm missing something, just ask.

Both methods work, it's just which one you prefer. I am more comfortable cutting wires than cutting vacuum hoses. If you are opposite, then cut away on the hoses.

Incidentally, one of the reasons my method works is because the vacuum control is mechanically linked to the vent location switch. The electrical system never knows where the blower is sending the air.

-salsbr

 

Salbr, I have an idea you could help me with. I would like to cycle the A/C compressor for highway use something like 1 min on 2 min off, but have the off time adjustable. It would work like intermittent wipers. This would help FE when the inside is getting to cold but you don't want to introduce warm air to warm the car or lower the blower speed. Sort of a poormans auto temp control.

 

What do you have in mind? It sounds to me like you want an analog input, say a single turn potentiometer, and something to enable the AC. The real question is how do you want to control it? How would it interact with your current controls?

And then, of course, what would you like from me?