Recharge Didn't Work; Now What?
 

:help: Admittedly not much of a wrench at all here, so any advice and help will be most appreciated.

2000 F150 4.6L, 89000 miles. Central Florida; A/C used everday. Temperatures now in the mid- to upper-80's with near 95% humidity.

A/C seemed to start 'dying' about a month ago. Takes quite awhile to begin blowing what could even be considered as cool air, but never cold air. Have not checked temp, but even when it's blowing its coolest, it is nowhere near what it was even a month ago. Seems to blow nothing but the humid ambient Florida air for several minutes upon start-up.

The compressor now cycles non-stop on about 5-8 second intervals.

Tonight I went to Wally World and picked up a can of ID's Measure and Charge thinking it just might need recharged (thanks to this board for the instructions!).

When the compressor activated, the gauge needle went into the blue (apparently properly filled); when the compressor deactivated, the needle went to the green (low). Not knowing which to believe, I hit one tiny squirt in the system and the needle jumped into the mid-yellow range when compressor active.

I disconnected and drove her around the block waiting for the miracle to occur, but no change.

Is there anything else I can do (with very limited abilities), before I take her into an A/C specialist or the stealer?

Thank you!

Is the compressor still rapidly cycling? You may have a temperature blend door problem hiding behind the low refrigerant charge.

Still No Cold Air
 

Waited a couple days just to see if anything changed.

In a word, nothing!

Compressor still cycling on/off very frequently; seemingly ambient air blowing for the first several minutes of operation; only cool air (not cold) when at its peak.

Is it time to bite the bullet and have it looked at by a pro?

P.S. I'm no wrench, so anything beyond basics is out of my hands.

Thank you.

Add a little more refrigerant if the compressor is still rapidly cycling. Another 10-12 ounces should do.

I have the exact same symptoms on my 2001 4.6l V8 SCREW.
The AC used to work fine, but died. Now blows ambient (or maybe very slightly cooler, but maybe not).

The compressor cycles, but fairly rapidly (5-8 secs sounds about right).
The control knob seems to work OK (recirc on max AC, non recirc on AC), and the heater works fine, so I've ruled out the blender flap.

In a another thread I read about the possibility of a vacuum leak. If I listen behind the battery when the control is on AC I can hear a slight hiss, which goes away when I turn the control to VENT.

When I look at the bundle of vaccum lines back there there is one black tube that is not connected to anything. There is nowhere obvious that it could have come from.

Does anyone have a vacuum schematic they could send me?
Could a vacuum failure cause these symptoms?
I might try to take a photo of the offending tube and post it tomorrow.

What is the insulated black tank behind and below the battery? Is that the vacuum tank or is that somewhere else?

Thanks!!

Overcharge Danger?
 

Quentin,

Thank you for the responses.

I'm concerned that if I put another 10-12 oz in, I will have overcharged the system.

When I put the small squirt in the last time, the gauge included with the Measure and Charge jumped into the low end of the yellow.

Can I trust the gauge with the Measure and Charge can?

What are the dangers if the gauge is correct and I really do overcharge the system?

Thanks.

Guages (as in a manifold gauge set, not the rinky-dink ones that come with charge cans) in general aren't really an accurate way to determine how much refrigerant is in the system. They'll give you a general idea of what the system is doing and whether it's under or over charged, but that's about it. The only way to know for certain how much refrigerant is in there is to reclaim it using a charging station.

If it was overcharged, worst case is that the pressures may spike high enough to open the pressure relief valve on the manifold line at the compressor and dump some of the refrigerant until pressures are back within normal limits. It might not cool too well if it's overcharged too. But if the compressor is still rapidly cycling at hot idle, I'd say that it's at least 10-12 ounces low, if not more.

That May Have Been It
 

Okay, I put what I would guess to be 75% of the 19 oz. can into the system and lo and behold, the compressor stopped cycling as rapidly as it had been.

When I got back in the cab to shut down, I could have sworn I was getting cooler air than before (although it may have just been wishful thinking!).

Tomorrow will be the true test when the temps and humidity of Florida climb back up to near-unbearable levels.

Quintin, thank you for your guidance and wisdom. :bows:

Kewl. Keep us posted. :)

Question for Quinton: How long should the compressor run with eng at idle with AC on max? Mine runs abt 30 secs and then off abt 4 and then back on for another 30

That depends. Hot engine, at idle, the compressor shouldn't be cycling. If the ambient temps are relatively low, the compressor may cycle more often to keep from freezing the system up. 30 seconds on/off, I'd dare say your system may be a tad low. How cold is the air coming from the vents?

I didn't tell you the whole story. On my 99 f150 I started to get the same symptoms that PaulRevere had I was following your advice to him and I put in abt 10 oz of 134a which improved the air temp quite a bit from what it was when it was cycliong every 5-8 secs. Its bearable now I haven't placed a thermomitor at the vent yet but air feels pretty cold after a few mins with the 30 sec cycle. It sounds like I need more 134a. How much do you recommend? Is it normal for it to go in slowly like in watching paint dry? I appreciate your advice.

Quintin: I checked the temp at the vents. Ambient temp hovering around 80f at 9am with high humidity vent temp 52f. Eng not hot but warming up and compressor only runs for 10-11 secs in high fans/max cool mode. It hasn't been that hot here for the past few days. Normally in low 90's gonna be abt 85 today they say

At this point, it's tricky to say. It should be a little cooler than 52 degrees at the vents though. And at hot idle, the compressor shouldn't cycle very often. Try another 8-10 ounces of 134a, sometimes it takes a bit for the system to suck it in.

Tks Quintin. I'll pick up another can and let you know what happens, gotta go to NC for a few days so I probably won't get her done till I get back. it is cooling alot better than it was before I put the 134a in yesterday. Tks again.