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Old 07-30-2014, 02:39 PM   #1
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Dash AC max pressure

Does any body know what the max pressure I should see on the high pressure side? I know you need cooling air through the condenser but what happens when you are stuck in traffic and the engine isn't hot enough to turn the fan on?
I'm seeing 350 to 400 psi without the cooling air.
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Old 07-30-2014, 02:50 PM   #2
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dash ac max pressure

I think those pressures you're seeing are getting dangerously high.

Many coaches have an electric fan to blow air over the condenser. This fan turns on as soon as the dash AC switch is turned on. If yours doesn't have this, should be pretty simple to add one.
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Old 07-30-2014, 04:03 PM   #3
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Quote:
Originally Posted by rommel View Post
Does any body know what the max pressure I should see on the high pressure side? I know you need cooling air through the condenser but what happens when you are stuck in traffic and the engine isn't hot enough to turn the fan on?
I'm seeing 350 to 400 psi without the cooling air.
The fan should always be turning, slowly when the engine is cold and faster as it warms up. There may be something wrong if it doesn't turn at all. There are many threads on this so you may want to search this forum for more info.
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Old 07-30-2014, 04:33 PM   #4
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Almost all A/C installations have electric fans (or radiator ducted fans) blowing over the condensing coils. They should switch on when the A/C is turned on. Often if you turn ignition to on but don't start engine, the electric fan(s) can be heard.
Often there is a high pressure cut out switch, just like the low pressure switch, that shuts the compressor clutch off when out of range. Your pressures do sound high, but you have to factor in temperature:

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Old 07-30-2014, 05:03 PM   #5
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Short answer is that your freon pressures appear pretty high. Longer answer is that there is at least one full night of reading on this forum concerning dash A/C issues on Alpines. It would also help if you mentioned the model and year of your Alpine--03s and earlier use a mechanical wax valve, while 04s and newer use an electronic controller to govern engine fan speed and air flow.
PS--no electric fans are involved!!!!!
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Old 07-31-2014, 11:32 PM   #6
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I believe the wax valve is on the 04s & electronic fan control started in 05
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Old 08-01-2014, 06:45 AM   #7
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EM--perhaps, I know the 03s have the wax valve and the 05s do not.....
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Old 08-01-2014, 10:10 AM   #8
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If he's sitting in traffic and doesn't see a serious rise in engine temperature, I'd think his fan is working. I'd check the location of the condenser. If it's in with the radiator, inner cooler and transmission cooler it could be dirty and needs cleaning. If, like mine, it's off to the right side with electric cooling fans, it could have a bad fan or be dirty.
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Old 08-01-2014, 01:19 PM   #9
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BF-this is strickly an "Alpine" issue--involving mechanical wax valves and electronic fan controller interfaces....kinda hard to guess on this one unless you have an owners' tee-shirt [smile]--appreciate the interest though.....
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Old 08-01-2014, 01:30 PM   #10
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Quote:
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BF-this is strickly an "Alpine" issue--involving mechanical wax valves and electronic fan controller interfaces....kinda hard to guess on this one unless you have an owners' tee-shirt [smile]--appreciate the interest though.....
WELL EXXCCCUUUSSEE ME. An A/C system is an A/C system. When it is turned on, it should kick the fan to a higher speed for the added cooling needed. I don't think it matters if it's a wax valve or electronic controller, it does the same thing. I repeat, if he reports that sitting in traffic idling doesn't cause his engine temperature to rise, the fan controller is working. It could be a dirty condenser.

I was trying to bring the issue back to the OP's issue instead of arguing what type of controller he has on he radiator fan.
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Old 08-01-2014, 03:12 PM   #11
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OK--here goes...early Alpines uses a mechanical wax valve mounted in the side of the radiator to govern the engine fan, so only heat generated by the engine cause the hydraulic driven, side mounted fan to run. Even sitting in traffic on hot days, the Alpine diesel rarely call for significant fan speed. And since there is no interface, either mechanical or electric, between the AC freon pressure and the mechanical wax valve, the A/C system has no direct effect on the engine fan. Sorry if I hurt your feelings, I was trying to give you a graceful pivot point......
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Old 08-05-2014, 09:30 AM   #12
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OK guys, didn't mean to start anything. I should have posted that I have an 01 36' and it has only the wax valve. When the engine is below 170 deg the fan does not turn, once it gets above that temp it starts to turn and in most cases this is fine. But I was just curious about checking the freon pressures to see if it was fully charged. The local guy who does cars mostly, said he was seeing the high pressures and said I probaby have a blockage some where in the system. The fan was not turning at that time. When the engine is at idle it won't get above about 150 so I guess you have to run it down the road to get it to operating temp. Is there a high pressure cutoff? If so what is the high pressure switch set at? This is getting to be quite the learning experience.
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Old 08-05-2014, 09:53 AM   #13
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Ref my earlier input, my 03 has the wax valve config and has always been "troublesome" during hot weather. I've been curious why some early Alpine owners with wax valves have complained while many others havent. Could be that not all wax valves are calibrated alike--at start up my fan will not run until engine reaches ops temp, other may allow idle speed at startup--dont know.

Besides cooling efficiency, I have had to replace hoses and o-rings, and finally a compressor due to frequent over-pressure issues. Since installing the WRV-recommended aftermarket solenoid valve, most of my concerns are behind me. Though I still worry about the harsh fan starts caused by the solenoid and it impact on the drive shaft that connects the air compressor and hydraulic pump. Accordingly, I keep "looking" at an aux electric fan option.

To answer your question, there appear to be two pressure sensors on the ACME dash A/C system in our coaches [right next to the fitler/accumulator up front]. The lower one is the aux fan sensor that was not used by WRV but the one I tapped to control the solenoid--I think it comes on at 175 and shuts off at 125????? I added a small LED light on my dash to monitor solenoid activation--stopped at lights and slow traffic in warm weather, the solenoid triggers the engine fan quite often.
There is a second freon sensor located just above the first--my guess is that this one is probably the low freon pressure sensor that prevents the compressor from running until a minimum pressure is obtained during the re-charge process, or in the event of a leak. Its possible that this sensor also has a high limit too but it appears to be quite high as I have seen freon pressures in the mid-300s prior to installing the solenoid controller.
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Old 08-05-2014, 10:14 AM   #14
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If the wax valve is working for the engine, is there a way to move the condenser? If you can move it from the radiator, inner cooler, and transmission cooler you'd reduce heat load on them and it's certainly easy enough to use an electric fan controlled by the power for the compressor electric clutch on a condenser fan.
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