AC blows cold, then hot, then cold...

sebryce · 05-05-2006, 06:47 PM

Replaced a vacuum line from the intake plenum that leads to the rear right of the engine compartment... A/C now turns on but will blow cold air for 5 seconds then back to hot for the same. Back and forth seems to be the pattern, Any ideas?

BlazerLT · 05-05-2006, 08:33 PM

You need to get your refrigerant recharged.

You are seeing the compressor cycling on and off due to low refrigerant.

It has nothing to do with the vacuum line.

sebryce · 05-05-2006, 09:15 PM

From the inside of the cabin I can hear what sounds like a opening and closing of vent? The hot is really hot and it does blow cold in between. I have a '98, does this take the new refrigerant? appreciate your advice.

billibong · 05-05-2006, 09:20 PM

It takes the R134a. By a good recharge kit with a gauge and a can of refrigerant, they run about $25-30, but are worth it.

blazee · 05-05-2006, 09:26 PM

It sounds like it could be a blend door problem.

sebryce · 05-05-2006, 09:27 PM

Thanks for the advice! It is easy to recharge? or should I get some help... I just replaced the lower intake manifold gasket and injectors recently and would rather save a buck or two on this one as well..

Pulled down the glove box and switched the blower to floor then back to vent and could see the vacuum device working when I turned the switch. Not sure what the other noise I am hearing inside the cabin is, it just keeps going on and off? (or on and on) similar to a vent opening and closing? It seems be be left of the heater box somewhere but it is definately inside.

BlazerLT · 05-05-2006, 10:49 PM

Quote:

Originally Posted by sebryce

Thanks for the advice! It is easy to recharge? or should I get some help... I just replaced the lower intake manifold gasket and injectors recently and would rather save a buck or two on this one as well..

Pulled down the glove box and switched the blower to floor then back to vent and could see the vacuum device working when I turned the switch. Not sure what the other noise I am hearing inside the cabin is, it just keeps going on and off? (or on and on) similar to a vent opening and closing? It seems be be left of the heater box somewhere but it is definately inside.

Do you hear the AC compressor cycling on and off?

sebryce · 05-05-2006, 10:54 PM

Yes the compressor is going on and off. Hooked up a gauge and it's around 20-25 psi when the compressor clicks on. Where is the high side port? want to avoid that I read. Low side port is on the accumulator? just want to be extra sure.

BlazerLT · 05-05-2006, 11:49 PM

that is low pressure.

I believe you fill through the low side port, never the high side.

You can get refill kits from the auto parts stores that comes with a gauge and everything right on the can.

Do NOT do it without a gauge. Overfilling is much more damaging to seals than it being underfilled.

sebryce · 05-06-2006, 01:22 PM

Help! I recharged the refrigerant and now the compressor stays on and that part is good. BUT I still have Hot and Cold blowing out the vents in the dash. I can hear (behind the glove box) what sounds like a creaking door opening and closing. The vacuum device (that controls flow to the floor ) is not moving but it sounds like it is coming from inside the big black housing that the vacuum mounts on to. I am frustrated and would appreciate any help. Is this the blend door that Blazee mentioned? if so, how in the &*^* do I get to it and is it hard to replace? Here's something interesting... even when I turn the fan and everything should be off, the same noise (opening and closing) still takes place. Is there a vaccum line that controls this?

blazee · 05-06-2006, 02:11 PM

Do you have normal or auto climate control?

MT-2500 · 05-06-2006, 02:21 PM

Quote:

Originally Posted by sebryce

Thanks for the advice! It is easy to recharge? or should I get some help... I just replaced the lower intake manifold gasket and injectors recently and would rather save a buck or two on this one as well..

Pulled down the glove box and switched the blower to floor then back to vent and could see the vacuum device working when I turned the switch. Not sure what the other noise I am hearing inside the cabin is, it just keeps going on and off? (or on and on) similar to a vent opening and closing? It seems be be left of the heater box somewhere but it is definately inside.

It sounds like you have a air cond control problem.
But on the air cond recharge deal.
Do even think about one of the wal mart recharge death kits.
And if you do call 911 before using it .

IF IT IS LOW ON FREON.
I would suspect a major leak.
#1 Freon is non consumable, if it's not there then there is a leak
#2 A/C is a delicate balance between liquid/gas (low side/high side) and too much freon is just as bad as not enough
#3 If you are not prepared to buy a set of A/C gauges, and be willing to possibly buy a vacuum pump or a/c die and replace the proper components, then don't even waste your time.
#4 90% of the time your going to have to pull a vacuum, flush the lines and most the time replace the accumulator and the Orifice tube/expansion valve.
#5 The only easy fix is if one of the pressure switches is bad, there is no just add freon fixes.
#6 Please don't just add freon w/ a charging kit because you think it needs it, It doesn't work like that.
#7 These guys are a excellent source for help and if you listen to the procedures as you are told you will end up w/ some ice cold A/C, being hard headed is expensive.

http://www.autoacforum.com/
#8 And here is a link from AC kits.com to what a person needs to recharge an air conditioning.
A/C starter Kit
#9 Adding freon to a system that has a good charge can be dangerous and can cause you harm, if the pressures get to high and blow the freon can or something in the system.

sebryce · 05-06-2006, 02:38 PM

It has climate control on this '98... the things just keeps turning in there, hot, cold, hot and so forth. You can easily hear it creaking (opening & closing)? I can feel it when I put my hand on the black housing and I can't see anything moving.

blazee · 05-06-2006, 02:52 PM

Here's a picture of the blend door motor that was taken by Josh Barber:

If you have electronic climate controls, I won't be much help because I don't have the schematics for those.

Here's another thread with the same problem, you could ask Josh what he did about his:
http://www.automotiveforums.com/vbul...d.php?t=543981

sebryce · 05-06-2006, 03:02 PM

Thanks for the direction, man all of you know your stuff and you are big help!
I unplugged it and now have cold only. Thanks again. I will look to see how Josh eventually fixed his.

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