trying to charge a/c in 87 graduate - Alfa Romeo Bulletin Board & Forums
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post #1 of 19 (permalink) Old 07-16-2013, 06:40 PM Thread Starter
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trying to charge a/c in 87 graduate

Upon charging, compressor won't start. Don't see low pressure switch in wiring diagram or in system. Also there is what appears to be a high (?) temp switch in series with the comp clutch lead. Looks like possibly thermal protection and should be mounted on compressor, but it is just dangling near the rad. overflow bottle. This also does not appear in diagram. My next step will, of course, be to check for continuity and power to the clutch. Any thoughts? How much pressure is needed to trip the low pressure switch...if there is one? What should the pressure be in the system at rest and equalized?
Also, there is very little air blowing out of the center vents...much more from outer vents. Is this normal?
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post #2 of 19 (permalink) Old 07-17-2013, 03:35 AM
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Was the AC ever working? Could have a leak and be completely empty, if so you'll have to pull a vacuum to charge it once the leak is fixed.

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post #3 of 19 (permalink) Old 07-17-2013, 04:17 AM
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There is no low pressure cutout switch in this particular system.
Question: when you turn on the A/C system, does the electric fan in front of the condenser turn on?
From your description, what appears to be a thermal switch could indeed be a thermal switch. If so, it is not for the compressor but for the electric cooling fan. It turns on the fan should the under hood air temp reach a certain value. The switch should be mounted in the upper right corner of the fan shroud.

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post #4 of 19 (permalink) Old 07-17-2013, 04:30 AM Thread Starter
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System did have a bit of positive pressure and is now holding about 70 psi. I figured out the thermal switch but I wonder if the wiring was modified in the field; it is in series with the compressor. The condenser fan runs when a/c is switched on.
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post #5 of 19 (permalink) Old 07-17-2013, 05:47 AM
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High pressure is just as harmful as low p, it's possible it's overcharged and the switch is a hi/low and it has shut the compressor off.

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post #6 of 19 (permalink) Old 07-17-2013, 06:18 AM
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Sorry for not saying this before but there's no high pressure switch in this system either.

EDIT: The condenser fan turning on with the A/C switch is good in that it confirms both A/C system fuses are good, the temp controller is sending a call for cool signal and the fan relay works. The call for cool signal also provides power to the compressor clutch. So it looks like it may boil down to this non-stock device in the compressor power feed wire. With the A/C turned on, is there power on one side of this device and not the other? Is it possible to post a pic of this thing?

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Last edited by papajam; 07-17-2013 at 06:35 AM. Reason: add edit
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post #7 of 19 (permalink) Old 07-17-2013, 11:53 AM Thread Starter
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Jim, this is definitely the temp sensor that is to control the fan...should be ln the rad fan shroud. Someone, I think, field modified the wiring and put it in series with comp clutch lead. Makes no sense, but that is what it is. I am going to jump it out and see what happens.
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post #8 of 19 (permalink) Old 07-17-2013, 01:54 PM
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Well, having a normally open thermal switch in series with the compressor power wire that could certainly explain no power to the compressor!

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post #9 of 19 (permalink) Old 07-17-2013, 03:57 PM
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Quote:
Originally Posted by mgsteve View Post
Jim, this is definitely the temp sensor that is to control the fan...should be ln the rad fan shroud. Someone, I think, field modified the wiring and put it in series with comp clutch lead. Makes no sense, but that is what it is. I am going to jump it out and see what happens.
Yeah, if I remember correctly from when I had my 86 Spider, there should be a little clip on the fan shroud that holds it. I always thought it was a little goofy!

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post #10 of 19 (permalink) Old 07-17-2013, 08:07 PM Thread Starter
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Hey kevin, I just don't know why someone wired it in series with the comp! I'm going to investigate some more in the a.m. if its a bit cooler.
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post #11 of 19 (permalink) Old 07-18-2013, 09:53 AM Thread Starter
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okay, upon further checking, the wiring is correct. when the unit calls for cooling, there is voltage at the clutch, but the clutch does not pull in. there is continuity from the clutch lead to ground so it looks like the coil is OK. Does anybody have any experience with these clutches; does it perhaps need some WD 40 or some persuasion? Is there any way to determine the viability of the compressor without the nightmare of removing it?
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post #12 of 19 (permalink) Old 07-18-2013, 01:04 PM
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First can you turn the center by hand.
The thing is just a magnet but it if got rusted you might need to hit it up with PB blaster or wd40
But if the center will not rotate aka the compressor is frozen don't bother.
you can also change out the clutch with out discharging the system if the clutch can not be made to work.

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post #13 of 19 (permalink) Old 07-18-2013, 01:17 PM Thread Starter
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Omg...you need such little hands! I'll try to turn it by hand. Can you really get that clutch off in place?
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post #14 of 19 (permalink) Old 07-18-2013, 04:27 PM
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Quote:
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Yeah, if I remember correctly from when I had my 86 Spider, there should be a little clip on the fan shroud that holds it. I always thought it was a little goofy!

Kevin
Goofy? Tell me about it. Mine screws on!! No clip!

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post #15 of 19 (permalink) Old 07-18-2013, 04:28 PM Thread Starter
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Well, the center does turn. Do the three flat bars on the face of the clutch articulate on the pins to allow innerds to expand? Hopefully some wd40 will free that up. Should I be able to flex that with my fingers, if I can get in there?
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