A/C goes to defrost default upon high load

Tiny
CWZRD1
  • MEMBER
  • 1996 FORD RANGER
  • 2.3L
  • 4 CYL
  • 2WD
  • MANUAL
  • 200,000 MILES
A/C goes to default(defrost) upon high load(acceleration). Seen where it's a vacuum leak or accumulation tank/check valve. Replaced accum tank and no change. Upon further investigation realized that with fan off and AC/heater sector to off, if I change the temperature control from cold to hot doesn't blow but temperature changes (blows lightly). I have checked vacuum under hood and can't find a leak. Blend door doesn't make clicking noise like broken.
Tuesday, June 16th, 2020 AT 6:44 AM

7 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
Good morning,

I attached a diagram for you.

There is a check valve that prevents the loss of the vacuum on acceleration.

Check that valve.

Roy
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Tuesday, June 16th, 2020 AT 7:02 AM
Tiny
CWZRD1
  • MEMBER
  • 10 POSTS
How do you check it when it's in the accumulation tank?
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Tuesday, June 16th, 2020 AT 7:30 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
With the engine off, there should still be a vacuum in the tank to move the modes in the truck. It should not bleed-off.

Roy
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Tuesday, June 16th, 2020 AT 7:41 AM
Tiny
CWZRD1
  • MEMBER
  • 10 POSTS
Thank you.
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Tuesday, June 16th, 2020 AT 7:53 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
You are welcome.

Always glad to help.

Roy
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Tuesday, June 16th, 2020 AT 7:59 AM
Tiny
CWZRD1
  • MEMBER
  • 10 POSTS
How much vacuum am I looking for again Roy?
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Tuesday, June 16th, 2020 AT 8:02 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
At least 18-22 inches of vacuum.

Roy
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Tuesday, June 16th, 2020 AT 8:10 AM

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