99 Maxima poor cooling *SOLVED*

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cmilot6329
Posts: 19
Joined: Thu Oct 17, 2019 2:18 pm
Location: Mesa, AZ

Re: 99 Maxima poor cooling

Postby cmilot6329 » Sun Jul 12, 2020 6:18 pm

Ok checked the air mix door actuator under the dash. I can see when I move the slider from hot to cold it is turning and opening and closing the air mix door properly and all the way. So doesn't appear hot air from the heater core is getting mixed in.
robmaxfli
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Joined: Fri May 13, 2016 7:07 am

Re: 99 Maxima poor cooling

Postby robmaxfli » Sun Jul 12, 2020 6:53 pm

To verify that there is a blend door type issue , you could pull off the 2 heater hoses from the heater core, buy a connector/bridge to join those 2 hoses together. I just did this and it proved to be a blend door issue. This will take the heat out of the heater core so you can get a heat-free reading out of the vents.
Al9
Posts: 157
Joined: Tue Mar 10, 2020 3:26 am

Re: 99 Maxima poor cooling

Postby Al9 » Mon Jul 13, 2020 12:02 am

Or you could just turn AC on as soon as you start a cold engine, while the coolant is still cool. If you get anything better than 70F vent - and ideally this has to happen in a few secs with a brand new compressor and a properly charged and oiled system, more so when in the shade - reheating is your problem.
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Cusser
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Re: 99 Maxima poor cooling

Postby Cusser » Mon Jul 13, 2020 5:59 am

Al9 wrote:Or you could just turn AC on as soon as you start a cold engine, while the coolant is still cool. If you get anything better than 70F vent - and ideally this has to happen in a few secs with a brand new compressor and a properly charged and oiled system, more so when in the shade - reheating is your problem.


This.
cmilot6329
Posts: 19
Joined: Thu Oct 17, 2019 2:18 pm
Location: Mesa, AZ

Re: 99 Maxima poor cooling

Postby cmilot6329 » Mon Jul 13, 2020 9:12 am

Definitely not getting any colder with a cold engine so don't think it is an issue with the blend door. AI9, when you say reheating is your problem what does that mean exactly?

Thanks!
Al9
Posts: 157
Joined: Tue Mar 10, 2020 3:26 am

Re: 99 Maxima poor cooling

Postby Al9 » Mon Jul 13, 2020 11:06 am

What Cusser is saying. Reheating happens whenever air that has passed through a live evaporator is routed through a live heater core. Either done on purpose to get all glasses demisted at the snap of a finger, or unintentional (malfuctioning heater core valve/air flap/control mechanism or system).
cmilot6329
Posts: 19
Joined: Thu Oct 17, 2019 2:18 pm
Location: Mesa, AZ

Re: 99 Maxima poor cooling *SOLVED*

Postby cmilot6329 » Mon Jul 20, 2020 11:33 pm

**SOLVED**

Updated OP
Al9
Posts: 157
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Re: 99 Maxima poor cooling *SOLVED*

Postby Al9 » Tue Jul 21, 2020 2:19 am

Great, so you can see how correct TXV operation is critical with these systems.

You might now want to have the system recharged to the precise refrigerant amount through an RRR station as i said before. There's no "just about right" with these compressors at all. Specified charge weight, or you lose performance.

Oil plays an important part too. I hope you either flushed the system or adjusted the new compressor oil charge to the amount recovered from the old one, and that you used the required PAG 46 (thicker oil may separate from the refrigerant phase at lower temperatures inside the condenser, creating a boundary layer that hampers heat exchange).

Finally, another observation to be made is that replacement compressors often come with "universal" control valves. The replacement one i've bought for my car comes with a control valve that will control the suction pressure to 44 psi absolute under high discharge pressures, that is, a slightly higher than 34F evaporator temperature. The original control valve the car came with controls it to 42 psi absolute, that is, a 32F cold evaporator. "Hang meat" kind of AC might even be overboard especially if it means less mpg, but if the performance loss will be noticeable, i'll have to replace it (not immediately; if the compressor turns out to be faulty it might lose warranty if returned with a different/clearly tampered with CV).

You might also want to test the faulty TXV to understand how it failed. It's a matter of blowing compressed air through while you're cooling the disc up with a freeze spray. With one meant for a variable displacement compressor, the airflow is actually supposed to taper off slightly as it cools down and never cease completely, though a block type TXV in my possession (a Denso 447500-1600) just eventually snaps shut completely for some reason (on this one the adjusting nut comes screwed on almost fully, likely to give a really high superheat to a warm evaporator, and this ends up narrowing the modulating range; unscrew it slightly and it stops doing that) even though it's used with a variable displacement compressor and many scroll compressors. The genuine one for my car doesn't do that, airflow just tapers off slightly and you can see the metering pin inside move closer to the orifice but never close it fully, and my car has a variable displacement compressor too.
Last edited by Al9 on Wed Jul 22, 2020 8:21 am, edited 1 time in total.
cmilot6329
Posts: 19
Joined: Thu Oct 17, 2019 2:18 pm
Location: Mesa, AZ

Re: 99 Maxima poor cooling *SOLVED*

Postby cmilot6329 » Tue Jul 21, 2020 6:21 pm

Awesome thx for the additional info! Probably won't have this car too much longer so not sure the extent I wanna continue to mess with this. For now I'm happy just having some cool air again.

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