AC diagnosis with a/c manifold gauge readings
#1
06-26-2013, 09:31 AM
AC diagnosis with a/c manifold gauge readings
Need help troubleshooting, as I've hit my limit on how to debug
2004 Freestar with manual dual control front and separate rear control, 3lb 5oz is a full charge
initial comment - I'm used to thinking about systems with a single evaporator. Not really sure how the 2nd evap is plumbed / how it affects these readings. Feel free to educate me
initial condition: passenger side air feels cool (not cold), drivers side is cool sometimes and warm others
Step 1: driver blend door doesn't seem to be following controls reliably - replaced. Symptoms don't change
Step 2: noticed compressor cycling every 15 seconds or so. Checked pressures - were low (sorry, I failed to record specific readings at this point).
Step 4: verify current conditions after distractions:
------------------------------------
So at this point, I seem to be overcharged, trying to figure out what's next
Suggestions welcome
2004 Freestar with manual dual control front and separate rear control, 3lb 5oz is a full charge
initial comment - I'm used to thinking about systems with a single evaporator. Not really sure how the 2nd evap is plumbed / how it affects these readings. Feel free to educate me
initial condition: passenger side air feels cool (not cold), drivers side is cool sometimes and warm others
Step 1: driver blend door doesn't seem to be following controls reliably - replaced. Symptoms don't change
Step 2: noticed compressor cycling every 15 seconds or so. Checked pressures - were low (sorry, I failed to record specific readings at this point).
After 1 12oz can R134a:
lo = 38psi hi = 180 psi
ambient = 90F, engine idling, doors open, front AC full blast, rear AC off
compressor quits cycling
vent temperature = ~70F
Step 3: added 2nd 12oz can:lo = 38psi hi = 180 psi
ambient = 90F, engine idling, doors open, front AC full blast, rear AC off
compressor quits cycling
vent temperature = ~70F
lo = 50psi hi = 205 psi
ambient = 90F, engine idling, doors open, front AC full blast, rear AC off
kids require help - have to walk off for several hours
ambient = 90F, engine idling, doors open, front AC full blast, rear AC off
kids require help - have to walk off for several hours
Step 4: verify current conditions after distractions:
vent temp is 61F with an 86F outside ambient
lo = 37psi hi = 255 psi
ambient = 86F, engine 1800RPM, doors open, front AC full blast, rear AC off
big external fan pushing air into the grille
lo = 42psi hi = 275 psi
ambient = 86F, engine 1800RPM, doors open, front AC full blast, rear AC full blast
Step 5: tentatively add 3rd 12 oz canlo = 37psi hi = 255 psi
ambient = 86F, engine 1800RPM, doors open, front AC full blast, rear AC off
big external fan pushing air into the grille
lo = 42psi hi = 275 psi
ambient = 86F, engine 1800RPM, doors open, front AC full blast, rear AC full blast
vent temp is 70F with an 86F outside ambient
lo = 41psi hi = 281 psi
ambient = 86F, engine 1800RPM, doors open, front AC full blast, rear AC off
big external fan pushing air into the grille
lo = 48psi hi = 325 psi
ambient = 86F, engine 1800RPM, doors open, front AC full blast, rear AC full blast
lo = 41psi hi = 281 psi
ambient = 86F, engine 1800RPM, doors open, front AC full blast, rear AC off
big external fan pushing air into the grille
lo = 48psi hi = 325 psi
ambient = 86F, engine 1800RPM, doors open, front AC full blast, rear AC full blast
------------------------------------
So at this point, I seem to be overcharged, trying to figure out what's next
- Blend door is okay, but maybe heater core valve isn't shutting off?
- LO pressure really low enough? Maybe an expansion valve stuck open?
- Guess it might be smart to check the rear vent temperature- haven't looked at this
Suggestions welcome
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