AC not so AC any more... recharge?

shoobs99svt · Jul 20, 2007

99 cobra w/63k

Air conditioning started slowly blowing warmer about a month ago. Could still hear compressor on/off and engine surge at idle etc etc... used ac again frequently last week and only warm air came out. looked underneath compressor doesnt turn but is free to move when by hand. engine DOES however surge a little at idle.

I went ahead and bought the el cheapo R-134a recharge kit (gauge/valve etc.) and took a stab at it. When I hooked the gauge up to what i still think is low-side charge point (5 or so inch forward of accumulator) it read about 140psi (motor was running for 10 min with ac on full blast)? Instructions said to NOT service anything higher than 45psi so i backed off and came here. Ideas?? Bad (el-cheapo) gauge??

ps compressor clutch fuse GOOD
acc belt GOOD

Uncle Meat · Jul 20, 2007

Sorry, wish I could help.... I know NOTHING about automotive A/C systems.

U.M.

Price1 · Jul 20, 2007

Low pressure switches frequently go bad. That switch is on the dryer. Remove the wiring plug and use a paperclip to jump the plug once you remove it. If the AC clutch now actuates when you turn on the AC (watch it and see if it engages when you do this) then you have a bad low pressure switch. It's an easy fix - screw the old one out and the new one in.

There are some good automotive ac forums out there, too.

Price1 · Jul 20, 2007

Oh, and I'm sure you were on the high-side port. High side is typically 150+ while low side is 25-40. The high side port is a larger diameter than the low side port. Also, you ONLY add refrigerant through the low-side port. Check the other port and see what the reading is.

shoobs99svt · Jul 21, 2007

Price...

Yeah ive been up to my eyebrows in the whole low pressure switch forums and how much of a gem that little piece is. first off i pulled more hair out trying to find without a doubt which port is the low side... it makes sense the low side shouldnt be putting out 140psi (this morning cold start 90-100 psi btw). so iwent ahead and put the same gauge on what i thought was the "low side" and it would not fit, at all. i do remember somewhere reading the low-side port is smaller diameter high-side much larger. there we have it. (ps i took pics gimme a day ill post)

went ahead and jumped the low pressure switch like you mentioned sure enough compressor spun cold air spewed. good. what suprised me is that the low pressure port went from 90psi(RED) down to about 30psi (lower but still in the norm FILLED) in about 3 minutes at idle. im really not too sure if that means there is another problem or not, but im stoked to have it easy enough to swap that little switch for now. ps cant seem to find a posted spec on what psi is norm under there, at all.

that said, haynes manual doesnt have any steps whatsoever for taking r/r that switch. do you have any tips, part numbers, or such?? looks like it unscrews off of the dryer with about a 9/16" not sure if im seeing that right. thx

shoobs99svt · Jul 22, 2007

<a href="http://photobucket.com" target="_blank"><img src="http://i53.photobucket.com/albums/g51/shubinj/Picture004.jpg" border="0" alt="Photo Sharing and Video Hosting at Photobucket"></a>
low side is left, just past strut tower

<a href="http://photobucket.com" target="_blank"><img src="http://i53.photobucket.com/albums/g51/shubinj/Picture006.jpg" border="0" alt="Photo Sharing and Video Hosting at Photobucket"></a>
80psi

<a href="http://photobucket.com" target="_blank"><img src="http://i53.photobucket.com/albums/g51/shubinj/Picture007.jpg" border="0" alt="Photo Sharing and Video Hosting at Photobucket"></a>
30psi

Price1 · Jul 22, 2007

Glad you found out the problem.

That low pressure switcy just simply screws out. Sometimes you can actually screw it off by hand. Screw a new one in. Try these auto AC sites:

http://www.acsource.com/

http://www.acpartsnow.com/default.asp?srcheng=google

http://www.airpartsonline.com/

One of these sure could help you. Also, this can be purchased at the dealer, too.

Hope this helps.

Mike

AntL97Cobra · Jul 23, 2007

Good post!!! My A/C has been blowing warm air for I dunno how long. I don't use it much at all because it's a convertible, still I'd like for it to work. I appreicate the pictures Shoobs99SVT, gonna try to get a recharge kit tonight and see what the reading is on my Cobra. Anymore info on where the low pressure switch is on the dryer or even a picture?

Thanks

shoobs99svt · Jul 25, 2007

The low pressure switch is right on top of the dryer (mine is horizontal facing towards the drivers side) and unscrews with a crescent and/or 5/8". seems the plastic expands only when tight on dryer making it too big for 5/8".
<a href="http://photobucket.com" target="_blank"><img src="http://i53.photobucket.com/albums/g51/shubinj/Picture005.jpg" border="0" alt="Photo Sharing and Video Hosting at Photobucket"></a>
auto zone part # MT0444 is $11.99
orig part reads F5VH-19E561-AA 9911
a/c blows cold now, problem solved

AntL97Cobra · Jul 26, 2007

Hey Shoobs, thanks again for the picture and part number information. Just to make sure I'm understanding correctly, that's the low pressure switch circled in yellow in the picture below??

shoobs99svt · Jul 31, 2007

yep thats it

AntL97Cobra · Aug 19, 2007

Mr Shoobs99svt.....you're the man!!!! It worked, it was the low pressure switch!!! Your description of the problem and the pictures you provided were very helpful, much thanks to you for all your help.

SVT32VDOHC · Aug 27, 2007

Price1 said:
Low pressure switches frequently go bad. That switch is on the dryer. Remove the wiring plug and use a paperclip to jump the plug once you remove it. If the AC clutch now actuates when you turn on the AC (watch it and see if it engages when you do this) then you have a bad low pressure switch. It's an easy fix - screw the old one out and the new one in.

There are some good automotive ac forums out there, too.

+1 I had a 97 Cobra 2 years ago. A/C would work one day, then it would blow warm for the next few, and so on and so forth. The switch on the drier solved my problem. It took 1 minute to unscrew and replace. They are the same on all fords, I got mine from a Windstar minvan. (No free-on comes out when you unscrew it either)

MusfangCobra · May 25, 2009

I replaced this switch today and now have wonderful COLD a/c!!! Great post thanks a billion.

SVT32VDOHC · Jun 1, 2009

2 year old thread still saves the day! SN FTW!

timeless2 · Jun 1, 2009

Correct me if I'm wrong, guys, but I think this A/C setup is the same for the SOHC. I need to pressure test (and likely charge) my Roush also.

SVT32VDOHC · Jun 2, 2009

timeless2 said:
Correct me if I'm wrong, guys, but I think this A/C setup is the same for the SOHC. I need to pressure test (and likely charge) my Roush also.

They are pretty much the same. The funny thing is, my computer says 6cyl, 8cyl SOHC, and 8cyl DOHC condensors are all different. This is not true. As long as you stay within certain years, they are all the same. I put a 6cyl condensor in Hack Job with all the 4.6L SOHC stuff and it worked fine....there was no difference.

Early cars have the quick disconnect tools at the condensor and the newer cars have a threaded bolt. There are still quick disconnects on a/c lines, just not at the condensor.

As far as a/c compressors....these are all the same:

Cougar '97 8-280 (4.6L)
Lincoln Mark Series '97-98
Mustang '97-04 8-260 (4.6L)
Mustang '05-06 4.6L (3V)
Thunderbird '97 8-280 (4.6L)

And as for the pressure switches talked about in this thread...like I said in my first post, all Fords use the same switch. I have had a bad pressure switch on an old 97 Cobra. Also, the clutch/bearing assy went bad on Hack Job. I put another used clutch/bearing assy on and it was fine.

jeremy canter · Jun 2, 2009

where can I get a clutch bearing set-up new if I need one ?
and how much is a new switch?

John00Stang · Jun 3, 2009

jeremy canter said:
where can I get a clutch bearing set-up new if I need one ?
and how much is a new switch?

New switch is $10.20 at o'reilly's and the pn is 36486. Not sure about the clutch, im sure they carry that as well.

Now to keep an old post going...lol. what if youve done the swich, drained and re serviced the refrigerant and the a/c still wont blow cold, low pressure line gets cold and thats it...? thanks guys.

SVT32VDOHC · Jun 3, 2009

jeremy canter said:
where can I get a clutch bearing set-up new if I need one ?
and how much is a new switch?

Should be able to get that at the AP store. I just put a used one on because I work at a yard, so we have all types of Mustang parts here. It's on bolt and you need snap ring pliers to take it off.

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