Jump to content

New Facebook Pages

Ford Mach E

Ford Thunder

  • Custom Search


  • 0
waynezo

AC Problem 08 Milan 4 cyl 83k

Question

Compressor is short cycling. Still cooling the cabin, but poorly. I checked Refrigerant.  It
is not low.  I suspect the AC clutch switch.  I found it on the smaller high pressure tube
near the firewall.(part# MOTORCRAFT YH39 Alternate/OEM Part Number(s): 6E5Z19D594AA)

Is this the only pressure switch or are there 2?  Is there a way I can diagnose with out
putting in the shop.  Looks like I can change the switch myself.

When the compressor is engaged air is ice cold.  What else would cause these symptoms?

Any advice is greatly appreciated. 

Share this post


Link to post
Share on other sites

7 answers to this question

Recommended Posts

  • 0

You need a set of pressure gauges and a scan tool to accurately diagnose this.

Do you have all your cabin fan speeds?   

Share this post


Link to post
Share on other sites
  • 0

Autozone will lend me manifold gauges.  can you recommend a good tutorial for diagnosis.  All fan speeds work on control head.

Share this post


Link to post
Share on other sites
  • 0

What are your running pressures when the clutch kicks out? Does that agree with the AC pressure sensor as read by the PCM? Does the AC evaporator temp sensor agree with the outlet temp at the vents?  

Share this post


Link to post
Share on other sites
  • 0

 

 

I measured with manifold gauges with ambient Temp at 86 degrees.

The low side is 40 to 45 (sometimes as low as 35) with compressor engaged then goes up to 60 after compressor kicks off.
The high side is 200 to 210 then down to 175 after comp kicks off
Static reading is low side 100 high side 125 

Does that indicate a low side switch?

The schrader valve on the low side access port has a slow leak I noticed after removing the gauge. The cap seems to be holding it for now. Is there a way to get it to seat properly without replacing it?

Share this post


Link to post
Share on other sites
  • 0

I tightened the schrader valve and it stopped leaking.   Early this morning with ambient temp at 75 degrees I got 35 lowside and 157 highside.  After adding approx 4 oz of refrigerant with ambient temp at 80 degrees I get lowside 40 and highside 225.  AC is still short cycling.  Should I worry system is now overcharged?

Share this post


Link to post
Share on other sites
  • 0

There is no low side switch. There is a high side pressure sensor and an evap temp sensor. Your pressures look ok. Now you need a capable scan tool to compare your pressure to the pressure sensor and watch the temp sensor, and PCM commanded clutch control vs actual. 

Share this post


Link to post
Share on other sites
  • 0

Thanks for all the great advice. 

My car has the expansion valve. I spotted it on the firewall where the lines attach.

One other symptom I have had. Previously When sitting at a red light in gear when the compressor kicks on the engine shudders. Since I have noticed it short cycling it shudders less. Could that be a sign of the compressor wearing out and putting less strain on the engine?

What is a good scan tool?  I'm guessing I would have to buy that.  Autozone probably won't loan it.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×