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Old 09-27-2015, 11:53 AM   #1
242Bleek
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Default 83 245t-AC goes warm under boost

Hi, I Just brought this car back from the dead and never really knew how the AC worked. I recently put a new old stock york compressor on it and the ac blows somewhat cold at idle, I know its not going to be very cold being a york using 134. But when I take off and get into boost its seems as if the ac completely shuts off as long as I'm at full or part throttle and will start blowing cold again when it comes back down to an idle. Seems like the higher the RPM's the warmer it gets gradually.

Not only that but when I get into boost the ac blower fan will divert all the air to the floor vents, and starts working properly again once out of boost, I realize this could be because its losing its vacuum signal but how could it keep a vacuum signal under boost? The check valve is good. This car has a B21F intake if that makes a difference.

Was wondering if somehow these two issues could share the same root cause or if any has ever seen this before. Thanks.
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Old 09-27-2015, 12:13 PM   #2
MistrThou
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You may have a bad vacuum check valve. The door actuators are controlled by engine vacuum. If you have none, they don't function. You may also have a vacuum leak under the dash somewhere.
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Old 09-27-2015, 02:35 PM   #3
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If I am not mistaken isn't there an AC compressor interrupt when under high boost? The idea being when you need to pass someone or suddenly accelerate the AC compressor clutch is disengaged so maximum engine output is given to accelerate.

I forget exactly what pressure interrupts the AC clutch but I am certain this functionality is normal. Perhaps you interrupt switch is faulty or needs adjustment and causes the clutch to disengage at to low of a boost level?


************************************************
Update

I found the green book that talks about it.

Is the installation instructions for B21FT intercooler.

It says the vacuum switch should cut out the AC compressor at 8 +/- 0.3 PSI and 3000 RPM.

Feel free to PM me your email and I send you a copy of the green book.
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Last edited by smoothdurban; 09-27-2015 at 02:50 PM..
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Old 09-27-2015, 09:31 PM   #4
242Bleek
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Quote:
Originally Posted by smoothdurban View Post
If I am not mistaken isn't there an AC compressor interrupt when under high boost? The idea being when you need to pass someone or suddenly accelerate the AC compressor clutch is disengaged so maximum engine output is given to accelerate.

I forget exactly what pressure interrupts the AC clutch but I am certain this functionality is normal. Perhaps you interrupt switch is faulty or needs adjustment and causes the clutch to disengage at to low of a boost level?


************************************************
Update

I found the green book that talks about it.

Is the installation instructions for B21FT intercooler.

It says the vacuum switch should cut out the AC compressor at 8 +/- 0.3 PSI and 3000 RPM.

Feel free to PM me your email and I send you a copy of the green book.
Thats wierd, this car was not factory intercooled, I added one and did not add that switch to it. It seems like it cuts off much sooner than 8 psi, almost right away when boost begins to register.
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Old 09-28-2015, 11:07 AM   #5
dobber13
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Quote:
Originally Posted by smoothdurban View Post
If I am not mistaken isn't there an AC compressor interrupt when under high boost? The idea being when you need to pass someone or suddenly accelerate the AC compressor clutch is disengaged so maximum engine output is given to accelerate.

I forget exactly what pressure interrupts the AC clutch but I am certain this functionality is normal. Perhaps you interrupt switch is faulty or needs adjustment and causes the clutch to disengage at to low of a boost level?


************************************************
Update

I found the green book that talks about it.


Is the installation instructions for B21FT intercooler.

It says the vacuum switch should cut out the AC compressor at 8 +/- 0.3 PSI and 3000 RPM.

Feel free to PM me your email and I send you a copy of the green book.
Not to steel the thread but does the newer type compressors that replace the York in a 240 have the same interrupt switch?
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Old 09-28-2015, 01:02 PM   #6
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It's not the compressor.
On the very very last of the 240T factory TIC cars on the rack of relays behind the driver side headlight (only present on those cars), there are 3 relays:
-Turbo+ "IBS" (Intercooled Boost System) relay for ~+2psi above 3720rpm to the 10.5 from 8 or whatever. (different looking relay in a different location, but does the same thing as it's earlier larger squarer shaped cousin over by the coolant bottle usually on dealier TIC models).
-2x bosch 5 pin relays, one for the aux pusher fan with a temp switch in the lower radiator hose, 1 for the A/C interrupt, which I believe is done at +3PSI and over 3720RPM since the wiring runs over to the 3psi firewall switch for the A/C cutout relay. +8psi would be nice, however, but I don't think there's any switch that senses +8psi.

The rotary compressor has a higher redline draws a lot less power. I probably wouldn't keep the A/C interrupt in that case. Ironically, the old york thing draws so much more power you probably have to use a little more boost to power, it, which would then mean you'd be more likely to engage the cutout.

I don't think they really wanted to to be revving the old york compressor over 4K much at all.

But if not factory TIC or if they didn't add that cutout dealie to your car's electrical, IDK. I've seen it on dealer intercooled cars once in a while, but rarely.
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Old 10-02-2015, 07:35 PM   #7
242Bleek
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Thanks for the input, I clamped off the inlet hose going to the heater core with vise grips and now the AC works phenominal all the time Sorry to waste your time with the AC issue. Im guessing this is a bad heater control valve that cant hold the coolant back when it builds pressure with RPM?

Also the vacuum check valve was bad, replaced it and this corrected the issue of the ac going to the floor.
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