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Need a little help with AC Ford 4.6

Posted By: laserred96gt

Need a little help with AC Ford 4.6 - 12/22/18 04:13 PM

The AC in my 04 E150 started acting up a couple of weeks ago, basically it runs good for about 5 minutes than suction line starts to freeze and the compressor clicks on and off constantly.
My initial thought was a restriction, I connected my gauges and pressures seem good but high side needle fluctuated rapidly. I evacuated the system, removed old orifice tube, ran nitrogen through the system, replaced the orifice tube, pulled a good vacuum and still does the same thing, what could it be??

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Posted By: Chris142

Re: Need a little help with AC Ford 4.6 - 12/22/18 04:33 PM

Jump the low pressure switch. See if it stays on. If it does what are the pressures?
Posted By: mattd

Re: Need a little help with AC Ford 4.6 - 12/22/18 04:54 PM

What are the pressures? Are you sure that is the correct orifice tube?
Posted By: laserred96gt

Re: Need a little help with AC Ford 4.6 - 12/22/18 05:26 PM

I don't remember the pressures right now but basically weighed in the the charge, 40 Oz's, the orifice tube I got at O'Reilly, looked just like the one that came out.
Posted By: mattd

Re: Need a little help with AC Ford 4.6 - 12/22/18 05:31 PM

The reason I ask about the orifice tube is that most fords use either a maroon or blue The reason I ask about the orifice tube is that most fourth use either a maroon or blue tube. I would look it up by application to verify. Exact pressures would be more helpful other than what it weighed in at. Have you ever added some type of stop leak to the system? The color looks strange unless you added some type of stop leak or orange dye

Is the fan operating properly?
Posted By: laserred96gt

Re: Need a little help with AC Ford 4.6 - 12/22/18 05:49 PM

Yes there was dye in the system, must have been the previous owner, I have owned the van since 2011 and never had a problem with the AC.
Blower motor is working, it is not blowing as hard as it used when I first bought it though.
I will check the pressures and read them next time.
Posted By: mk378

Re: Need a little help with AC Ford 4.6 - 12/22/18 05:50 PM

Orifice tube systems work by controlling the low side pressure to avoid freeze-up. The boiling point of R-134a varies with pressure. If the pressure is not allowed to fall below about 25 psi, the evaporator won't get cold enough to freeze.

There are two ways to do this. The simple one is to have the low side switch cycle off at 25. Thus the compressor cycles during normal operation. The more sophisticated version is a variable compressor with internal pressure control so it stops pumping below 25. In this scheme, the compressor should not normally cycle. There is a low pressure switch that turns off around 10 to protect against running the compressor in case of a total leak-out.

As others said the pressures are the way to diagnose this.
Posted By: mattd

Re: Need a little help with AC Ford 4.6 - 12/22/18 05:54 PM

When I said fan I mean condenser/radiator fan
Posted By: laserred96gt

Re: Need a little help with AC Ford 4.6 - 12/22/18 06:30 PM

There's are a couple of pictures of the pressures with the compressor on and off.

low side reads 30psi/+1
High site125psi/+15

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Posted By: laserred96gt

Re: Need a little help with AC Ford 4.6 - 12/22/18 06:41 PM

.

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Posted By: mattd

Re: Need a little help with AC Ford 4.6 - 12/22/18 07:14 PM

Those pressures aren’t bad the high side is on the low side are you sure the system is properly charged? What is the ambient temp? Also when you see the suction line freeze the compressor cycle off? At whatlow side pressure does that happen? If they stay at those pressures it shouldn’t cycle off. It won’t cycle off until less than 10-15psi or less on low side.

Make sure the cooling fan clutch isn’t frozen making it run all the time
Posted By: FSully1

Re: Need a little help with AC Ford 4.6 - 12/22/18 09:45 PM

Need ambient temp......looks under charged, if no compressor issue.
Posted By: Kode

Re: Need a little help with AC Ford 4.6 - 12/22/18 11:24 PM

I would look at some sensor as the culprit.
Posted By: Colt45ws

Re: Need a little help with AC Ford 4.6 - 12/23/18 01:26 AM

Im gonna say there isnt enough charge in it and thats why its freezing up.
Posted By: WyrTwister

Re: Need a little help with AC Ford 4.6 - 12/23/18 03:08 PM

Originally Posted by laserred96gt
Yes there was dye in the system, must have been the previous owner, I have owned the van since 2011 and never had a problem with the AC.
Blower motor is working, it is not blowing as hard as it used when I first bought it though.
I will check the pressures and read them next time.

If the evaporator blower is not moving enough air , it can affect the suction pressures . Maybe , even to the point of freezing the coil .

If the condenser blower is not moving enough air , high pressure will be too high .
Posted By: bdcardinal

Re: Need a little help with AC Ford 4.6 - 12/23/18 11:41 PM

Originally Posted by laserred96gt
Yes there was dye in the system, must have been the previous owner, I have owned the van since 2011 and never had a problem with the AC.
Blower motor is working, it is not blowing as hard as it used when I first bought it though.
I will check the pressures and read them next time.


Fords tend to have dye from the factory.
Posted By: DONWATERS

Re: Need a little help with AC Ford 4.6 - 12/24/18 03:43 AM

I say dirty leaf clogged evaporator core.
Posted By: clinebarger

Re: Need a little help with AC Ford 4.6 - 12/24/18 03:52 AM

If this van has Auxiliary A/C.....It's way undercharged at 40 ounces.
Posted By: laserred96gt

Re: Need a little help with AC Ford 4.6 - 12/24/18 11:36 PM

No it is a cargo van, it only takes 40ozs, yeah what im leaning at is a partially clogged evap in combination with lower ambient temperature and weak blower motor not moving enough air across the coil. Noticed early this morning when it was colder outside that lines started freezing right away, I also noticed the problem the first cold day we had in Florida.
Posted By: laserred96gt

Re: Need a little help with AC Ford 4.6 - 02/12/19 11:21 AM

Sorry to bring back an old thread but found the problem to be a bad low pressure switch, hopefully this will help someone, thank Chris and everyone for their replies.
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