Proper vent temp for A/C?

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Jul 20, 2007 | 07:57 PM

#31

lsrx101

Fleet Mechanic

Joined: Feb 2006

Posts: 1,776

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From: Lorain County, Ohio

Quote:

Originally Posted by cbbass123

Weird you say cycling switch....i just replaced that today cause it was messed up and would not turn on compressor. I would have to fiddle with plug and tap switch to make it turn on compressor...but that is fixed compressor stays on...no frosties...temp about 90 to 95 around here

Ok. That all sounds good. Remember, at that ambient temp, the compressor will not cycle (rarely). Lets see if we can get the vent temps down. Those trucks easily do low-mid 40s at 90 degrees.
I need some info:
-Originally R12 or R134? Converted?
-What color was the orifice tube you installed?
- If converted, what brand fan clutch did you use?
-Is the fan shroud in place and not broken?
- At 1500 rpm, feel the inlet and outlet pipes on the evaporator. Are they the same temperature? Is one colder tham the other?
-It's possible that you have heat bypassing the blend door in the dash. Clamp off the heater hoses and see if the vent temps drop lower or if there is any change in the AC.

Let me know what you find.

Jul 21, 2007 | 04:04 PM

#32

cbbass123

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Joined: Sep 2006

Posts: 33

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From: Texas

Quote:

Originally Posted by lsrx101

- Yes, Originally R134
- Orfice tube color, can't remember, tech ordered for my year of truck
- Purchase Hayden severe duty (pt # hdn 2783)
- Fan shroud in place and not broken
- Not sure on what inlet pipes or outlets, but the pipe that runs from compressor to cylinder thing is cold and the outlet thing is cold(sweaty cold) the black box on firewall there are also pipes where orfice located, those pipes are hot and inlet beneath orfice into the black box is cold.
- how would i clamp off the heater hoses, would that make difference?
Please let me know. Thanx

Jul 21, 2007 | 10:18 PM

#33

lsrx101

Fleet Mechanic

Joined: Feb 2006

Posts: 1,776

Likes: 5

From: Lorain County, Ohio

Quote:

Originally Posted by cbbass123

All of that sounds good.
You should check the evaporator pipes right where they go into the "black box". If the larger one is noticably warmer than the smaller one, you're undercharged a bit.
Clamping the hoses off is a test to see if you have heat leaking into the cold air stream. C clamps work well, put a chunk of wooden paint stick on both sides of the hose and clamp then down to close off the coolant flow. If the outlet temp falls, you have a blend door issue. It's best to start out with a cold cooling system so you're not waiting for the heater core to cool.

Jul 23, 2007 | 08:17 PM

#34

cbbass123

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Joined: Sep 2006

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From: Texas

just a follow up...I have yet to have time to bypass the heater hoses, today it rained/cloudy and while driving...ac was blowing cold...and on stop warms up a bit...my question is...why is my compressor constantly running...what makes it do that? is there something else i myself could check
thanks

Jul 23, 2007 | 09:25 PM

#35

lsrx101

Fleet Mechanic

Joined: Feb 2006

Posts: 1,776

Likes: 5

From: Lorain County, Ohio

Quote:

Originally Posted by cbbass123

In rainy/cloudy conditions, regardless of ambient temp, the AC will work better in general. It's when the sun is bright and the humidity is high,(and engine RPM is low) that it's hardest to get MVAC systems to cool well.
It almost sounds like you're undercharged, but the compressor shouldn't be running constantly if that were the case. (look at the clutch at 1500 RPM under the hood).
Can you get a manifold gauge set and verify the pressures? It's important, now, to see what's going on inside the system.
If the system was working right, with that new Hayden fan clutch, you should only note a very slight difference at idle. (if at all). The temps should be down in the 40's.
Clamp off the heater hoses, first thing. (Vise Grips and paint sticks (or other suitable devices). The idea is to clamp off the hose and not damage it. If it's the original hose from 95 and really stiff, well....

Jul 31, 2007 | 12:08 AM

#36

Peter94

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From: St. Peter

Sorry guys for not responding. I just got back from vacation, we took my GF's moms truck up (ext cab 94 F150) and that thing is ALOTALOT ALOT colder than my truck for a/c. I have not had the time nor the money to get a genuine fan clutch from ford. I"m actually afraid to call and ask how much they are. But once I get my head above water financially I should be okay.

lsrx101 or anyone: just a side question i've been having problems with a 98 cadillac catera. The high side service port leaks, It looks like the whole fitting unbolts from the line. Is this true? what exactly is needed to replace the fitting. It looks like a rubber bulb in the fitting instead of a scrader valve? whats the deal with that.

Jul 31, 2007 | 12:19 AM

#37

lsrx101

Fleet Mechanic

Joined: Feb 2006

Posts: 1,776

Likes: 5

From: Lorain County, Ohio

lsrx101 or anyone: just a side question i've been having problems with a 98 cadillac catera. The high side service port leaks, It looks like the whole fitting unbolts from the line. Is this true? what exactly is needed to replace the fitting. It looks like a rubber bulb in the fitting instead of a scrader valve? whats the deal with that.[/QUOTE]

That high side fitting will unscrew from the line, BUT you will lose all of the refrigerant if you unscrew it (and likely hurt yourself). Those valves will leak a little bit. The service port CAP is actually the primary seal on those service fittings. Make sure the seal in the cap is good (about $2 from GM for a new one). Don't use an aftermarket cap, they WILL leak.
If it has leaked down enough to affect the AC operation, you will need a gauge set to "top off" the system properly. If you don't have a gauge set, you need the system in a vacuum and charge the correct amount by weight.

BTW, cbbass123 hijacked the thread and kept it alive. We didn't forget about you in your absence.

Last edited by lsrx101; Jul 31, 2007 at 12:31 AM.

Jul 31, 2007 | 10:42 AM

#38

Peter94

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From: St. Peter

There is no refridgerant left in the car. It leaks enough to loose about 24 oz in about 1/2 an hour. I have access to a vac pump, and I have the manifold gauges. I'm guessing something is messed up with that rubber seal though.