Air Conditioner doesn't stay cold..

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2005.Neon.SXT
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Air Conditioner doesn't stay cold..

Post by 2005.Neon.SXT » Tue Jul 23, 2013 6:22 pm

Not sure where to put this, but it's a real quick question.

When I'm driving, lets say on a trip, and I have the a/c blowing... it's nice and cold for maybe 20 minutes, but then it doesn't seem to blow as hard as it should (when it's on the appropriate dial). I have to turn it off, roll windows down, wait about 15 minutes, then I can turn the a/c on and everything's back to normal... until 20 minutes go by again. To put it in perspective, it seems like there's something blocking the fan... so the air seems restricted. Still cold, but doesn't matter what fan speed it's set... it doesn't blow hard.
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Post by dvon17 » Wed Jul 24, 2013 4:58 am

resistor going bad?
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Post by sidepipe87 » Wed Jul 24, 2013 7:31 am

It may be that it's freezing up and thus not blowing cold air anymore
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Post by r/tguy02 » Wed Jul 24, 2013 9:07 am

^ what ryan said, mine did the same thing, not sure why it freezes up though.
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Post by 2005.Neon.SXT » Wed Jul 24, 2013 12:25 pm

So there's nothing that can be done? I figured it was freezing up... but wasn't sure if there was a fix.

Thanks for clearing that issue up though :thumbup:
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Post by bigbird » Sat Jul 27, 2013 9:27 am

My 05 does the same thing on long trips. I'm sure it's freezing up. I hope someone finds a reason this is happening.
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Post by 2005.Neon.SXT » Sat Jul 27, 2013 10:29 am

Glad I'm not the only one. Love how cold my a/c gets... but only for a short moment... lol.
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Post by JeffM » Sat Jul 27, 2013 12:04 pm

Weird. Mine will cycle, I imagine while it recharges, but it won't just drop off.

But then again, I rarely use my A/C. :lol:
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Post by bigbird » Sat Jul 27, 2013 10:46 pm

it may be the low pressure switch, but I'm not an AC man.
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Post by Hazardsneon » Sun Jul 28, 2013 2:59 pm

I have the same problem. I run just the fan and it gets gradually better. This seems to work but i also hope there is a fix.

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Post by Hazardsneon » Mon Oct 07, 2013 11:09 pm

I've been thinking about this but haven't had a chance to get on the forums in a while. Forgive me because I'm not completely in the know about A/C systems but is there a drain for the condensation that forms on the condenser that is in the cabin? I seem to remember a lack of condensation running from my car during the summer after using the A/C. My wife's Jetta takes a leak all over during the summer but my 02 neon doesn't seem to share a squirt. If the condensation has no where to go and starts freezing, it could cause a lack of air flow.

It doesn't really matter now being that the summer heat is over but I thought I would throw in my 2 cents.

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Post by occasional demons » Mon Oct 07, 2013 11:42 pm

Yes, there is a drain. The system is designed so the evaporator won't get cold enough to freeze water, for that very purpose. The condensation would freeze before it got to the bottom of the HVAC box.

If there is a malfunction tho, it might get cold enough to freeze, and block airflow.
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Post by Hazardsneon » Tue Oct 08, 2013 9:22 am

What kind of system malfunction could cause it to get too cool? It seems like it is a possibility because, like I had previously posted, I am able to get the air flow back up if I run just the fan for a while. This makes me think that it is freezing and melting. Also, where about is the drain for the evaporator?

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Post by occasional demons » Tue Oct 08, 2013 10:05 am

I haven't researched it enough to know exactly how they control the pressure/temperature on the modern systems/neon. On the 70's/80's cars, they limited the pressure in the evaporator so it wouldn't get below freezing.

Basically in simple terms this is how it was done.

With refrigerant it a pressure to temperature ratio. R12 was kind of a 1:1 ratio. If the pressure was 70 psi, the temperature of the refrigerant was ~70ºF. If you pull a vacuum, ie: low pressure on it, it will get cold. So the amount of low pressure was what was regulated.

But if the valve got clogged, it could freeze solid. If it wouldn't close enough, the evaporator wouldn't get cold enough.

The drain is on the lower firewall, towards the passenger side. It is a rubber elbow that points downward. There need not to be excess liquid in there to freeze the evaporator. Just frost build up from freezing condensation will do it.

If there was enough water to cover the entire core, it would have flooded the carpet in the cabin well before it got to that point.
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Post by 04R/T » Wed Oct 09, 2013 3:55 am

This may sound strange, but your system is probably undercharged a bit.

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Post by Hazardsneon » Wed Oct 09, 2013 7:29 am

I checked the pressure and its right on the money. I dont recall what the pressure was but it was good.

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Post by occasional demons » Wed Oct 09, 2013 10:14 am

04R/T wrote:This may sound strange, but your system is probably undercharged a bit.
Not if you understand the pressure/temperature relationship. :lol:
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Post by titansxt » Wed Oct 09, 2013 10:51 am

My 05 SRT does something similar, as do a lot of other 05 Neons. It will run fine cold but then periodically it will get warm. I'll just shut it off for a few minutes but nothing nearly as drastic as 20. I've heard about it being the pressure switch more than a few times.
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Post by sidepipe87 » Wed Oct 09, 2013 12:50 pm

titansxt wrote:My 05 SRT does something similar, as do a lot of other 05 Neons. It will run fine cold but then periodically it will get warm. I'll just shut it off for a few minutes but nothing nearly as drastic as 20. I've heard about it being the pressure switch more than a few times.
This is the same culprit as my brother's 05 and I'd guess the same with others as well.

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Post by thttxboy » Wed Oct 09, 2013 7:47 pm

I had this problem recently in my 04 and yes it was freezing up just slightly enough to start restricting air. Put my gauges on it and I can't remember what the psi was but it was hanging out right around 38 degrees and well freezing is 36 degrees so I guess while driving it would drop. Anyways the case was I aded just enough to get it to 42 degrees or so and no issues since then

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Post by Donkeypuncher » Thu Oct 10, 2013 1:51 am

Is it true that you should never have to recharge the A/C system unless there is a leak somewhere? I've been told that by a lot of people, but I've also heard that the charge can get depleted after years of use.

Mine gets kind of cold after running it on the highway for 20+ minutes, but probably doesn't get below 70 degrees.

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Post by occasional demons » Thu Oct 10, 2013 7:25 am

The only way it gets "depleted" is from a leak. I used to have an old Frigidaire fridge from 1938 that worked great up to the day the compressor died. That was about 2002 ish, so about 60 plus years is far longer than most of our cars will last, let alone never needing A/C service.

Psssst.... Juan, water freezes at 32ºF :lol:
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Post by MichNeon » Fri Oct 11, 2013 11:45 pm

The a/c systems in the 1st gens had a temperature probe in the evaporator fins that helped to prevent the evap from freezing up. The 2nd gens don't have that probe, they use the low pressure switch to regulate the temperature, by way of the low side pressure. The pressure has a correlation with the temperature.
As Occasional said, if you understand the pressure/temp relationship, you'll understand how it works.
Another thing to remember, refrigerators, freezers, home a/c units usually run for years on the original charge of refrigerant, due to the fact that they sit in one spot, they don't move. Cars and trucks move around, and as such, there is a lot of movement of the components, so they develop leaks, which leads to problems and having to be recharged.
For those who want to learn and understand the a/c system on our cars, Doug95Neon did a really good writeup on a/c, it is on the neons.org, here's a link~ http://forums.neons.org/viewtopic.php?f=125&t=365596
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