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View Full Version : Plugged in A/C gauges, can anyone confirm my suspicion about this issue? (Vid inside)



CaifanSC
06-08-2016, 10:03 AM
Howdy all,

So after fixing the brake lines on the teal car I noticed the AC temps were not as cold as before. The car did sit for a few months through the winter while I fixed the brake lines. So did some reading, took out the gauges and this is what I found. Can anyone confirm my suspisions?

From the vid below and from reading the 94 shop manual, I believe my freon pressures are within specs for a full system. Visual inspection does not show any leaks that I can perceive. Am I interpreting this correctly? The ambient temperature was about 80*F. I was not able to test output temperature from the vents inside the car bc I didn't have one of those thermometers handy. This would rule out low freon.

IF this is correct, then by the shop manual, the issue is pointing to a faulty compressor cycle switch, correct?

Thanks for any input!



https://www.youtube.com/watch?v=mvge83aTW9w&feature=em-upload_owner

KMT
06-08-2016, 11:02 AM
System thinks it's a tad low on freon, so add some, then if no joy, I'd wonder if bad switch or plugged orifice tube or excessive air gap on A/C clutch. Switch is low hanging fruit, so after adding freon, I'd do that and confirm air gap next.

Would be nice to know the temp out of the middle vent, tho ;)

DrFishbone
06-08-2016, 12:12 PM
If the compressor cycles on and off that fast (clutch should keep it engaged all most all the time or all the time), probably just need to add some refrigerant. I would add a little dye too, unless you know there is already some in the system. You probably have a slow leak somewhere.

I would think it would be unlikely that a pressure switch would fail such that it interpreted the pressure wrong...much more likely either failed open or closed. Won't know until you add some refrigerant though!! :)

TBirdJKC
06-08-2016, 12:34 PM
I would think it would be unlikely that a pressure switch would fail such that it interpreted the pressure wrong...much more likely either failed open or closed. Won't know until you add some refrigerant though!! :)

The pressure switch in my 95 Bronco caused the compressor to cycle like crazy before getting stuck open. Same FS10 compressor (different pulley) and same part number pressure switch as a 95 Thunderbird. So I wouldn't rule it out just yet. If I remember correctly, the switch was super cheap. Something like 6 bucks at the local Autozone. Took 5 minuets to swap and the compressor went back to a normal cycle routine.

DrFishbone
06-09-2016, 12:16 PM
The pressure switch in my 95 Bronco caused the compressor to cycle like crazy before getting stuck open. Same FS10 compressor (different pulley) and same part number pressure switch as a 95 Thunderbird. So I wouldn't rule it out just yet. If I remember correctly, the switch was super cheap. Something like 6 bucks at the local Autozone. Took 5 minuets to swap and the compressor went back to a normal cycle routine.

Good to know! They certainly can get gummed-up before getting completely stuck.

CaifanSC
06-09-2016, 06:25 PM
Thanks for the input gents! The pressure switch seems to be very easy to change so I have a Motorcraft replacement in order. From the shop manual the cycle sensor is only supposed to be hand-tight, is that correct?

The old one seems to have a dirty connector and the blades in the old sensor don't look too clean...but since its easy to swap, might as well rule that out. If that doesn't do the trick - and if I'm interpreting the pressures correctly- i should need very little freon no? Would a small bottle do? I think its 8 oz?

KMT
06-09-2016, 06:37 PM
i should need very little freon no? Would a small bottle do? I think its 8 oz?

Vent temps....you may not need any or it might be time to vacuum it down, dry it out and refill to spec. Resist just dumping in 134...

CaifanSC
06-09-2016, 06:40 PM
Vent temps....you may not need any or it might be time to vacuum it down, dry it out and refill to spec. Resist just dumping in 134...

Ahh yess....i gotta stop by the parts store and get a thermometer. Thanks for the reminder bud! ;)

FrankenBird
06-09-2016, 11:35 PM
Ahh yess....i gotta stop by the parts store and get a thermometer. Thanks for the reminder bud! ;)

no hes not. hes gong to get one of those lighter plug in fans....fricken gangster to the fullest ..
but my guess would be a clogged or next to ac compressor \.

CaifanSC
06-12-2016, 06:47 PM
What do you think fellas?

Received the new cycle switch and replaced it. Tried again and still warm air. Got the vent output temps :D:D and they're below. Ambient temp today is at approx 92*. Should I go ahead and add freon?


http://i48.photobucket.com/albums/f226/Caifanito/A75FE25B-FD0F-4D41-9870-11F8A9E33C0B_zpswsqjrw9e.jpg~original (http://s48.photobucket.com/user/Caifanito/media/A75FE25B-FD0F-4D41-9870-11F8A9E33C0B_zpswsqjrw9e.jpg.html)

http://i48.photobucket.com/albums/f226/Caifanito/0B0AF09B-4C84-4B1A-8382-3C221C118303_zpsb1nmcmop.jpg~original (http://s48.photobucket.com/user/Caifanito/media/0B0AF09B-4C84-4B1A-8382-3C221C118303_zpsb1nmcmop.jpg.html)

http://i48.photobucket.com/albums/f226/Caifanito/E270FD6F-8238-4B92-BAD2-43BE557F0D77_zpsvwp0fitq.jpg~original (http://s48.photobucket.com/user/Caifanito/media/E270FD6F-8238-4B92-BAD2-43BE557F0D77_zpsvwp0fitq.jpg.html)

http://i48.photobucket.com/albums/f226/Caifanito/7B41EC9D-1ADA-4066-AA16-4D697164F9E9_zps0v0bwc1y.jpg~original (http://s48.photobucket.com/user/Caifanito/media/7B41EC9D-1ADA-4066-AA16-4D697164F9E9_zps0v0bwc1y.jpg.html)

KMT
06-12-2016, 06:54 PM
Nice switch.

Are those temps with the doors and windows closed? Is it still short cycling?

Did you check the air gap on the compressor clutch? Either of the lines getting cold where you can reach them?

CaifanSC
06-12-2016, 07:22 PM
Nice switch.

Are those temps with the doors and windows closed? Is it still short cycling?

Did you check the air gap on the compressor clutch? Either of the lines getting cold where you can reach them?

Yessir doors and windows closed. Haven't checked gap....how would that have changed if no work has been done to the compressor? Wear?

KMT
06-12-2016, 07:29 PM
Right - wear.

Maybe it was close to max spec last time it worked and now it's out of spec. Easy to check with a feeler gauge is why I suggested finding out.

Same as any repair, info is your friend.

CaifanSC
06-13-2016, 12:13 PM
Looks like it was low freon in my case. I checked the compressor clutch gap and was within the specs I found browsing the forum. I had a large can of freon so put that in. It was enough to increase the pressures to the spec in the chart below (which is higher than what's in the Ford shop manual). One can was enough to stop the compressor from cycling and to get me back to cool temps! Picking up more freon today to top it off. Looks like pressure is still a little low and hopefully will result in slightly lower output temps at the vent.

I'll have to keep my eyes open for leaks in order to make sure there are no other big issues present.

http://i48.photobucket.com/albums/f226/Caifanito/C15A69E3-8724-49F6-846C-E023382162F5_zpsgaeomc0g.jpg~original (http://s48.photobucket.com/user/Caifanito/media/C15A69E3-8724-49F6-846C-E023382162F5_zpsgaeomc0g.jpg.html)

http://i48.photobucket.com/albums/f226/Caifanito/Temp-pressure-chart-33776F1_zpspcjx3h7y.jpg~original (http://s48.photobucket.com/user/Caifanito/media/Temp-pressure-chart-33776F1_zpspcjx3h7y.jpg.html)


https://www.youtube.com/watch?v=IAlackMVIdU&feature=em-upload_owner

KMT
06-13-2016, 12:29 PM
Terrific, nice job - you 'da man ;)

Now keep an eye out for leaks.

TbirdSCFan
06-15-2016, 11:39 PM
You can get colder temps out the vent if you tweak the pressure switch to pull a lower "low side" cycling pressure. The lower the pressure, the colder the evaparator core. You're shooting for as cold as possible w/o freezeup. Freezeup happens when water in the air condenses out onto the evap core and freezes. This continues until the core is blocked with ice and as a result, no longer allows air to pass through. Generally, 32 is lowest, but it can be even lower. A low side pressure for that is in the 20psi range. This is what I have mine set for. Your stock pressure switch may be calibrated for actual freon. (BTW, you aren't using freon(r12), its r134a... there is a difference).

Here's how you check this. Run the A/C on coldest setting, with the low side guage hooked up. watch it drop down until you hear the compressor disengage and note the reading. If its 30 or higher, you have a lot of room left for more cooling. Remove the connector on the switch, look inside and with a small screwdriver, adjust it 1/8 turn CCW and retest. Watch your high side pressure if you need to add more r134. needs to stay about 3x ambient temp. I run mine at 330 on 100 degree day and I get 36 out the center vent. :cool: