AC clutch

udidwht · Sep 16, 2022

Will need to adjust the clutch air gap on this Sanden U-7903 part#15680077. When I turn the AC on it will briefly squeal/chirp. I can see the clutch pull in but slip then engage fully.

Anyone able to tell whether this is keyed or splined?

Anyone know whether the armature will come off by hand once the nut is off?

Here's a shot of the clutch side...

someotherguy · Sep 16, 2022

Haven't done one so I don't know, but have you looked at Sanden's support info? Didn't drill down but it looks like what you're seeking may be here: https://www.sanden.com/servicemanual.html

In case the link doesn't show due to the http"S" - try www.sanden.com/servicemanual.html

Finding the specific measurement range for the clutch gap would be wise, too. You might eyeball it and get it close enough to work, but if it's too tight or too loose, might accelerate wear.

OK a quick drill down because I was curious:

7.2.2 Air Gap Check 1. Air gaps exceeding 0.051” (1.3 mm) can prevent engagement. This often is noticed after the clutch and compressor temperature is heated through normal use. Refer to section 8.2.6 for more information setting correct gap.

All of chapter 8 begins with clutch removal so I'd start there instead of going straight to 8.2.6. Looks like a nice thorough service manual.

Richard

udidwht · Sep 16, 2022

someotherguy said:
Haven't done one so I don't know, but have you looked at Sanden's support info? Didn't drill down but it looks like what you're seeking may be here: https://www.sanden.com/servicemanual.html

In case the link doesn't show due to the http"S" - try www.sanden.com/servicemanual.html

Finding the specific measurement range for the clutch gap would be wise, too. You might eyeball it and get it close enough to work, but if it's too tight or too loose, might accelerate wear.

OK a quick drill down because I was curious:

7.2.2 Air Gap Check 1. Air gaps exceeding 0.051” (1.3 mm) can prevent engagement. This often is noticed after the clutch and compressor temperature is heated through normal use. Refer to section 8.2.6 for more information setting correct gap.

All of chapter 8 begins with clutch removal so I'd start there instead of going straight to 8.2.6. Looks like a nice thorough service manual.

Richard

I was actually just looking at that when I noticed the keyed vs spline. Figured someone would be able to tell from my pic. Looking at the front of mine I do not see the (3) threaded holes but (3) flat nubs. So perhaps it's spline and can be removed by hand as the manual states:

8.1.2bSpline Shaft Armature-Removal

5. The spline shaft armature will not have threaded holes to
accept the armature puller

6. Lift off armature plate with fingers. If armature does not come
off easily, spray an anti seizes oil into shaft to
loosen. Armature plate can also be loosened by
gently prying between rotor and armature plate
with two flat screwdrivers.

udidwht · Sep 17, 2022

Confirmed the air gap is too wide. Spec is (.4mm - .8mm). It's at .9mm (engine cold).

Sanden manual for the SD7 states:

Air gaps exceeding 0.051” (1.3 mm) can prevent
engagement. This often is noticed after the clutch
and compressor temperature is heated through
normal use.

So once at normal use temp the gap grows enough that slipping when engaging will occur. Too much and it won't engage at all.

Also checked the field coil for resistance (spec is 2.8 - 4.3) mines at 3.2 (12 volt).

someotherguy · Sep 17, 2022

Were you able to get it adjusted within spec and working again?

Richard

udidwht · Sep 17, 2022

someotherguy said:
Were you able to get it adjusted within spec and working again?

Richard

Waiting for a puller to arrive. I was able to get the nut off though. This one is keyed with (3) threaded holes so a puller is needed which I did not have.

As for working it...it works great but once at operating temp if I turn the AC off then back on it will slip slightly (squeal/chirp) before engaging fully. First thing i thought of was the air gap and sure enough when the engine is cold it's out of spec (.9).

Anyone know what the gauge readings should be (ballpark) for the low and high say on a 70-75 degree day? I currently have a low reading of 38psi and a high of 250ish system is nice and cold. This is with (3) 12oz cans which according to the following chart is shows it as 2.75lb.

https://www.proairllc.com/pub/media/pdfs/eti-Refrigerant%20Charge%20Information%20-%20R134A%20Systems.pdf

Go by gauge reading or just put in 2.75lb?

udidwht · Sep 17, 2022

I'll add this in case anyone needs the info...

Compressor is Sanden U-7803 Part#15680077

Specs:

Air source #s:

Compressor - 5704
Clutch - 5138
Head - NSS
Model - 7H15
Fitting head - SJA
POS - Horz
Fitting size - O/R Pad
Mount - Ear
Diam - 125
Pulley groove - 2
Volt - 12v
Wire end - T5D
Shaft - Key
Oil cc's - 270

1998_K1500_Sub · Sep 17, 2022

udidwht said:
Go by gauge reading or just put in 2.75lb?

@L31MaxExpress has a method he uses based on "superheat"… that’s the proper technical term, but it's a simple process of measuring the temperature at the inlet of the evaporator, outlet of the evaporator and inlet to the compressor, and comparing them, or rather their difference, to a target value.

He's discussed this method recently in other posts (maybe even earlier in this thread, I should look). Perhaps he'll reply.

(edit) Here is his method. Start taking notes where he says "Properly charged...".

Sanden 4440 install

https://www.gmt400.com/threads/sanden-4440-install.58192/post-1249093

udidwht · Sep 20, 2022

Complete!
There were (2) shims underneath. Removed the larger of the (2) and reinstalled the clutch. Air gap is now .4XXmm. Runs beautiful and no more chirp/squeal after haven run a bit and turning off-on and/or cycling.

AC clutch

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