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I converted my air conditioning system to R-134 about three years back and overall it has been working pretty good.

Lately though....while driving down the road with nice cool air (at least initially), I notice that the air coming out slowly changes from being nice and cool to regular warm air. There is plenty of air still blowing, but it is no longer cool air...it just seems like warm outside air.

So...I switch it back to "Vent", or even to the "Off" position (I have the Electronic Climate Control panel), wait a minute or so while I am still driving down the road, and then back to "Norm A/C" or "Max A/C"....and sure enough, here comes the nice cool air again!!

I don't think I am low on refridgerant because the cool air always seems to come back time and time again. The blower is working fine because the air never stops blowing. Since I am driving down the road when this happens, it's hard for me to say if the compressor is still working or not.

In researching this problem...I see that there is a WOT A/C Cutout Relay. Is it possible that this relay could be causing the problem I described above?

Is there anyway to "test" this WOT A/C Coutout Relay to see if it is intermittent ?

Should I be looking at and considering other problem areas besides this subject relay?

Also....(and this is a little embarrassing), I am having a heck of a time trying to remove the WOT A/C Cutout Relay. I can't seems to get it loose from the little metal bracket that it is secured to. Is it clipped in there some how ? Any secrets to removing the WOT A/C Cutout Relay?

Appreciate any thoughts and comments...
 

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The WOT cutout is triggered by the computer, so I think it is highly unlikely that it is falsely triggering. Since you have electronic climate control, there could be a problem with the unit adjusting the position of the temperature blend door. I've seen this on several 94-97 MN12s with automatic climate control.
 

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When it stops blowing cold, pull over and check to see if the compressor clutch is engaged.
 

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I'd be willing to bet that it's low on refrigerant. Put some gages on it and hold the throttle @1500-2000 rpm. If the needle dips to around 28-25 psi, and the clutch disengages, then you are low and need a top off. Get a UV light and the glasses from the parts house and see where the leak is (more than likely it's the o rings).
 

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Don't our A/C systems on our MN12 T-Birds/Cougars have both high-pressure and low-pressure cut-off switches? If they do (I think pretty much all A/C systems do) and you have enough refrigerant, I'd check them.

I'm willing to bet you're low on refrigerant, though!

Dennis
 

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I found the opposite on my 92 SC.

After charging the AC with 134 conversion to max pressure, it would work fine until it got hot on a highway cruse, then as soon as I threw full boost at it, the cutout would shut off the compressor, but it would not re-engage until a few minutes later.

It did this regularly until I lowered the pressure by leaking a little 134 out, now it doesn't happen as often and still blows colds as 'a dead witches boob in a brass braziere'.
When it cuts out it won't re-engage until a few minutes, only when it's hot outside and the car is running at max temp, but far less often than when I had the max pressure in the AC system. I may need to drop the pressure a little more.

I think I've got something going on with the re-engage function but not sure where to start looking. I suspect an issue or normal function with the high-pressure switch but need to troubleshoot it more.
 

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I found the opposite on my 92 SC.

After charging the AC with 134 conversion to max pressure, it would work fine until it got hot on a highway cruse, then as soon as I threw full boost at it, the cutout would shut off the compressor, but it would not re-engage until a few minutes later.

It did this regularly until I lowered the pressure by leaking a little 134 out, now it doesn't happen as often and still blows colds as 'a dead witches boob in a brass braziere'.
When it cuts out it won't re-engage until a few minutes, only when it's hot outside and the car is running at max temp, but far less often than when I had the max pressure in the AC system. I may need to drop the pressure a little more.

I think I've got something going on with the re-engage function but not sure where to start looking. I suspect an issue or normal function with the high-pressure switch but need to troubleshoot it more.
You may have an issue with the low side switch....but to be sure, take it to a shop and have them pull out the 134 that is in it. They can tell you how much is in there and replace with the correct amount. Just a few ounces too much or too little can have a huge impact on A/C performance. If you don't weigh the cans while you are charging, you will get close, but won't be right. I use a digital kitchen scale and have an empty can to "zero" the scale. I can get within 2 oz of spec.
 

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Don't our A/C systems on our MN12 T-Birds/Cougars have both high-pressure and low-pressure cut-off switches? If they do (I think pretty much all A/C systems do) and you have enough refrigerant, I'd check them.

I'm willing to bet you're low on refrigerant, though!

Dennis
I know the low side cuts out at around 22-28 psi, closes at 40-47psi and the high side cuts out at about 420 psi and closes around 250 psi
 

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I have the same deal going on with mine. My AC pressure is good, and the system is fully charged. When I first turn it on, the AC is NICE and cold, then if I were to drive say 20+ miles it gets to the point that the ac is still working, just not blowing all that cold anymore, eventually getting to the point that it feels like the ac is just blowing outside temp air. Yes the compressor is still functioning at that point.

Do you notice that when you shut the car off, after having the air on, that there is a TON of water that dripps out from the system? Mine does that, almost like the drain tube is clogged and cant drain properly till the car is off and sitting. I thought it was coolant because I just did the intake, but it's not. It's condensation like what SHOULD be dripping out while the AC is functioning.
 

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There isn't a high-pressure cutout switch before 94. It only came on cars that came with R134a originally. Also, depending out blower motor speed, outside temperature and humidity, a properly charged system can disengage when the engine speed is held at 1500-2000 rpm.
 

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Does the ATC on older MN12s use an actuator for the blend door? I know my 94 used to go to warm sometimes and that could be fixed by turning the temp lower. It hasnt done it in forever though. Could be something with the controls or actuator. My 92 LS had a cable for the blend door so I cant attest to this. Another thing to thing about is a weak compressor clutch field coil. If the clutch isnt engaged, but its supposed to be (power supplied to the field coil), you can hit the clutch hub and make it engage the engine while the engine is running. I usually give it a push with a prybar when I try this. If it engages and stays engaged after that, you need to replace the field coil definitely, possibly the other clutch components just for fun.
-Rob
 
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