How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask K. Wiggins Your Own Question
K. Wiggins
K. Wiggins, ASE Certified Technician
Category: Jeep
Satisfied Customers: 2873
Experience:  ASE Certified Technician, Associates Degree in Automotive Technology, 15+ years in the trade
68360881
Type Your Jeep Question Here...
K. Wiggins is online now
A new question is answered every 9 seconds

2004 Jeep Grand Cherokee ac question? what's the best

Customer Question

2004 Jeep Grand Cherokee ac question?
what's the best way to test my ac system to see if it's cold enough? what are the steps I need to take to get accurate results I have a temp gauge for the vent and it is around 60 when its hot around 90 and maybe 48-50 on cooler days in the 70s
Submitted: 1 year ago.
Category: Jeep
Expert:  K. Wiggins replied 1 year ago.

Hello, you want to measure the outlet temperature with the thermometor at the outlet closest to the evaporator core. Usually it's the one all the way to the right on the passenger side. Outlet temp with the AC on recirculate and fan on high should be 36-40 degrees after around 10 minutes of the ac being on and traveling down the road at over 35mph. This inusures the system has had time to stabilize and good airflow over the condenser.

You can also check the high and low side pressures with AC on high and engine at 1500RPM I'll post the temp pressure chart below

Customer: replied 1 year ago.
how don't test the pressures? what does the pressures tell me?
Customer: replied 1 year ago.
thanks
Customer: replied 1 year ago.
can I use a can of 134 that is empty that has a gauge?
Expert:  K. Wiggins replied 1 year ago.

The pressures are used to evaluate the charge in the system Look on that chart at the ambient (outside) air temp and what the pressures should be.

You can use the gauge from the empty can.

Customer: replied 1 year ago.
with the empty can do I need to pull the trigger to read the pressure or should it read as soon as I put it on the low pressure side? should I check the high pressure side as well
Expert:  K. Wiggins replied 1 year ago.

It will read without pulling the trigger. It will only work on the low side port. If you want to read high side as well you will need a complete manifold gauge set. They can be bought on eBay fairly cheap. Seeing both high and low side pressure is very helpful in identifying problems and I do recommend checking both.

Customer: replied 1 year ago.
OK if I get one from Harbor freight can you explain how to check with that type a gauge thank you
Customer: replied 1 year ago.
if I check both high and low side pressures as you stated above on high at 1500 rpm should it be on recirculating too?
Expert:  K. Wiggins replied 1 year ago.

I can and with recirculate on

Customer: replied 1 year ago.
I bought a manifold set today at Harbor freight can you describe out how and what I should be doing and what I'm information I'm getting from this thank you
Customer: replied 1 year ago.
I also bought a 12 ounce bottle of our 134 a does it matter if I used two different brands in the system
Expert:  K. Wiggins replied 1 year ago.

You can use different brands of 134A.

Connect the blue hose to the low side , red to high side with valves closed. Crank up the jeep and turn AC on high. Allow it to run 10 minutes or so for everythingto stabilize.

Now's when you want to look at the chart below and what the pressures should be for your outside air temp. If it's just low on freon both pressures should be a little lower then what's listed.

This page explains the different readings and what they mean. If you're a litle unsure just let me know your ambient air temp and the pressure. Below is the chart with ambient temp in farenheit.

Expert:  K. Wiggins replied 1 year ago.

One other VERY important thing to note. DO NOT open the high side valve to add freon. Only open the low side valve to add freon to the system.

Customer: replied 1 year ago.
ok when I test it i will let you know. will this tell me anything else like if the system is not working right?
Expert:  K. Wiggins replied 1 year ago.

It will tell charge, if there's any restrictions and general health of the compressor

Customer: replied 1 year ago.
if I have to add to the system how don't know how much I am putting in?
Expert:  K. Wiggins replied 1 year ago.

You will have to watch the high side gauge. when it goes up 10-20psi close the valve and wait to see what the pressures go back down to. IT's best to add a small amount many times then add to much and cause too much high side pressure.

Customer: replied 1 year ago.
how do you stop it from entering? shit the low side off when I see the high side go up ?
Expert:  K. Wiggins replied 1 year ago.

That's correct. The high side is what you want to watch while the low side is open. When you are adding freon with the low side open the low side gauge does not show accurate system pressure. once you close the low side valve it's accurate within a few momentsl

Customer: replied 1 year ago.
thanks sorry for all the questions!
Expert:  K. Wiggins replied 1 year ago.

You're welcome, I'm happy to share how to do it safely and accurately.

Customer: replied 1 year ago.
it's 70-72 degrees out ac on max recirculating I hooked up both high and low to gauge and to ac system with couplers and manifold turned to off position.
then opened both sides on the ac and this is what I got for readings? what do you think?
Customer: replied 1 year ago.
I also hooked the yellow up to the manifold see picture
Customer: replied 1 year ago.
which side of the needle do I read
Expert:  K. Wiggins replied 1 year ago.

The high side looks fine, can you close both valves and take another pic?

Customer: replied 1 year ago.
if I close both valves I shouldn't get anything right? you mean both valves on the couplers on the ac right? because the two on the manifold are closed
Expert:  K. Wiggins replied 1 year ago.

I forgot HF gauges had valves on the couplers. OK with both closed on the manifold what the guages are showing is a restriction in the system.

Expert:  K. Wiggins replied 1 year ago.

You're going to need to change the expansion valve, it's stuck which is very common on expansion valve systems. It's located in te engine bay right on the firewall the two ac lines go into it. Once you change it out you'll need to vacuum the system and recharge it. The instructions are below

Customer: replied 1 year ago.
I will try and test it one more time in a few min just to confirm pressures again. I just want tom make sure I am doing his right..... close all 4 valves 2 on manifold 2 on coupler. run system on recirculating on high hook up couplers to high and low and only open the 2 coupler valves leaving then manifold valves closed and take a reading?could it just be low on freon?do you have an item number or know where I can buy this from if not
Customer: replied 1 year ago.
out side temp is 81 - 82
Customer: replied 1 year ago.
what do you think? how would you know if it was low on refridgant
Expert:  K. Wiggins replied 1 year ago.

If it were low on refrigerant the high side wouldn't be as high as it is. What's happening is the expansion valve is keeping the low pressure too low. You could add freon and what will happen is the high side will keep going up but the low side will not change much.

The Valve is FOUR SEASONS 39014 it lists for around 15-20.00 most parts stores will stock it.

Customer: replied 1 year ago.
would it still be some what cold? it is around 50 degrees
Customer: replied 1 year ago.
do you have any pictures of this item
Expert:  K. Wiggins replied 1 year ago.

Yes, it will still blow cool. The expansion valve just has a piston that slides back and forth to control freon flow. I'll post a pic below. Actually here's a video that shows it at the 1 minute mark different year but generally the same to change. You might as well do the accumulator as well

Click here

Customer: replied 1 year ago.
could you explain how to evacuate the system and how much it might require to fill?
Customer: replied 1 year ago.
thank you so much for the help with this I just figured it was low on Freon
Customer: replied 1 year ago.
but glad I got gauges and check it out
Customer: replied 1 year ago.
I just looked under my hood and that must be a different model then my 04 4.0 liter my evaporator is not next to my battery? maybe that video was with a 5.7 ?
Customer: replied 1 year ago.
is that my accumulator? I said evaporator before by mistake
Expert:  K. Wiggins replied 1 year ago.

That is the accumulator some may also call it the receiver/dryer.

By law the refrigerant will need to be recovered before opening the system. Once you have the refrigerant recovered you can change the parts and vac it. Some parts stores will rent you a vac pump or you can pick one up from harbor freight. The air powered one they have works fine with a decent compressor.

When you replace the accumulator you'll need to add 2.4oz (70ml) of pag oil. Also use pag oil to coat any O rings before installing them

You hook the vac pump up to the service hose on your manifold and open both valves, pull it down for at least 15 minutes then close the valves and make sure it holds vacuum.

Once that's done you can start charging. The freon capacity is 27oz so you'll need three cans but will use 2 whole cans and 3 oz of the last one. Basically put in the first two cans then watch the gauges closely when adding the 3oz from the last can. Walmart has regular 134A really cheap in 12oz cans, it's usually on the bottom shelf as they like to promote the more expensive ones with additives.

Expansion valve failure is really common in systems that use them. The piston inside the valve just wears out over time.

Customer: replied 1 year ago.
do you think I could just replace the valve and be good? also can you explain the difference between recover and vac
Customer: replied 1 year ago.
if info just change the valve do I need to coat anything with oil? or anything else that I would need to know.? once I add the last three oz I am watching the gauges to be the correct pressures for the given temp right? like we talked about before
Expert:  K. Wiggins replied 1 year ago.

More than likely you'll be fine just replacing the valve, just don't leave the system open long as the accumulator will absorb moisture in the air.

Recovery involves using an AC machine to pull out the freon so it doesn't go into the atmosphere put is rather stored in a tank for later use, as per EPA regulations. Most shops charge .3-.5 hr to recover. If you had them change the valve as well you'd be looking at .7hr to have that done.

Expert:  K. Wiggins replied 1 year ago.

That's correct on the last 3oz just check the chart and match the pressures to your temp

Customer: replied 1 year ago.
do you think I should not attemp the valve my self? can't I barrow a tank from the parts store and a vac?
Expert:  K. Wiggins replied 1 year ago.

The parts stores only loan the vac pump. The recovery/recycling machine will only be in a shop. You can likely call around and find a shop that will recover the freon pretty cheaply and even vacuum and charge it without charging for freon. Usually smaller shops are more friendly about things like this.

Customer: replied 1 year ago.
how bad of a job is it?
can't i just vac the system pull the valve replace it then recharge?
thanks! how do I send you a tip? after this is all done and said I would like to show my thanks for the help
Expert:  K. Wiggins replied 1 year ago.

It's not a bad job. EPA regulations require it to be recovered....

Vacing is done prior to charging in order to remove moisture from the system as it's not compressable like the refrigerant.

Once you accept or rate the service a box pops up to give a bonus.

Customer: replied 1 year ago.
ok I will call around and see how much to recover .if I would have tried to replace this part without recovering then tried to vac it what would happen?
Customer: replied 1 year ago.
if someone doesn't recover would they still need to vac
Expert:  K. Wiggins replied 1 year ago.

Nothing other than the freon coming out. If a hose is removed quickly and the freon contacts your skin it can cause frost bite.

Customer: replied 1 year ago.
the freon would be sucked in to the vac wouldn't it?
Expert:  K. Wiggins replied 1 year ago.

That's correct, it would go into the pump and depending on the type it would contaminate the oil in it or if air driven just go into the air.

It will need to be vacuumed. Vacuuming causes moisture in the system to boil off.