Climate Control Module
 

I am fighting my Z's climate control system. Currently all it will do is blow hot air out of the defrost vents. I have seen where a lot of people have had this problem but i have gone as far as to pull the dash out and replace almost all of the vacuum tubes and still nothing. I have just bought a new climate control module from 300zxpartsforyou.com. I'm hoping this is the problem cause i have run out of things to check. While i was ordering the new unit i noticed that there is a multitude of different units that look the same but have different identification numbers on it and i wanted to ask if anyone knew what the numbers meant?

Thanks
Michael

Date codes
 

I would Imagine those refer to build date codes and production revisions. As production proceeds on a new model, sometimes adjustments and changes are made, for a variety of reasons such as parts supply and vendor issues or possibly reliability issues. With those codes and a little research you can determine when a part was made. The basic operation of the unit would remain unchanged, but some of the internal parts could very slightly.

you got analog or digital system. makes a difference also turbo vs n/a. you say you pulled the dash and replaced vacuum hose. did you do the engine compartment? there is one hose that goes thru the firewall and then y's out to either side of the dash. that is your main vacuum supply for the system. no vac there nothing much works. the water control valve requires vacuum to close again if that hose is gone it will never shut off as wide open is the failure mode. did you download the fsm from xenon all is explained there. if you just want no hot air while you figure it out run a vac hose straight to the top of the water control valve mounted on or near the firewall at the back right corner of the engine

I have an 86 NA with the digital system. I did replace 3 hoses in the engine compartment, one from the vacuum port on the top of the engine to the vacuum tank behind the passenger headlight, one from the vacuum tank through the firewall to that T, and one from the solenoid on the vacuum tank to the watercock valve.

As of right now i have the hose that goes through the fire wall disconnected completely and moved the line to the watercock valve up to the firewall port so that the vacuum will close it and stop sending water to the heater core. With it like it is obviously there is no vacuum to those vents, but we put a can of R134a in to the system and it cools to about 50 degrees i think it needs one more can and that should be good.

So with the lines in their correct configuration what happens is i get only hot air out of the defrost vents even if it is in AC mode. which means the signal from the control unit is not opening the solenoid valve to close the watercock valve. I cannot change which vents the air comes out. I replaced most of the vacuum lines under the dash when i had it off but nothing changed. I messed up and put the bracket that holds the Climate control and the radio in before the dash so i am going to have to pull it back out anyway, and we are going to go over those lines again and check the wiring harness.

Under the vacuum tank is what i think is the Carbon Canister, and the line that goes over the fan and into the air intake is broken off at the canister could this be part of the problem? I think it is part of a separate system?

Also i have seen that some people have a vacuum pump. I think this is only for turbo models because when they get on boost they lose vacuum from the engine. I'm i correct or should i be checking that too?

Thank you
Michael

The line that goes to the firewall
 

Give the line to the firewall a direct connection to the engine, use a T if you have to, your carbon canister could be clogged, and I think it requires a direct connection, if not it won't hurt to know you are getting full vacuum at the AC controls.

We pulled a vacuum on the firewall line and it held until you turn the climate control on. Apparently i missed a bad line or we have a leaky solenoid. any other thoughts? Other wise i will re-post when i get time to pull the dash and check everything again.

Thanks
Michael

So we pulled the dash out along with the air box that has the heater core in it, and found that the vacuum motor that separates the air flow from the heater core has a leak in it. It is part number PS1-38-22 on 300zxpartsforyou.com. We could buy a new one from Steve at 300zxpartsforyou but we are a little leery of buying another part that is still 28 years old and works now but may go bad within a year. Has anyone retrofitted something else there that does the same thing?

Yeah, I have dealt with this stuff. It made me a big fan of recyclers, especially when Nissan OEM Central started discontinuing parts I really needed - and would have paid their ridiculous prices. "Sorry, no longer available."

I now recommend recycled Z components. I use them all the time and have never had a problem. Z parts work. That's why these amazing cars are still on the road! It makes no sense to me to put a new 30-yr-lifetime part in a car that is 28 yrs old.

You're still not too late to locate your Z model on a recycler's lot. Trouble is that heat/cool module is a pain to get to and remove. For your purposes, the one in a recycled Z would likely work just fine. If you find a recycler who has one - in a Z - you guys need to talk. My recycler here lets me remove stuff myself on the lot (!) :icon_eyes: My na and my turbo have so many recycled parts and run perfect, both of them. Used OEM is great.

Other solution is the guys on this site who are parting out that model. Only question is mileage - and condition. If the Z has been whacked seriously in the front, you could have a problem. Otherwise, ask them for it. The dash might already be taken apart.

For recyclers, check out car-part.com for a common part and sort results by distance from your zip. Call the listed recyclers and see if they have the Z there on the lot. Make a visit if possible. It could be a gold mine for you. Compare prices. You'll see what I mean.

Keep that beautiful Z on the road. ;)