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Old 10-02-2022, 04:22 PM   #1
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Join Date: Aug 2020
Posts: 21
Default 98 Sun Voyager 460 Ford No A/C and front defrost stuck on

Hopefully this will help someone else with their problem.
Symptoms: A/C was not blowing cold and the front windshield defrost air vents were stuck in the on condition.

First Thoughts: The elements here in SOCAL are pretty rough on RV's. I did not want the front boot to cook in the sun so I usually take it off when I park the rig. Over the years, the sun had baked some of the rubber and plastic components in the front compartment. I had to replace the engine coolant expansion tank and several of the hard plastic vacuum and rubber hose lines.

I tried to check the defrost vent actuator vacuum and it was zero. The line goes through the engine boundary into behind the dash. The temperature control is the old push button type which suggested the old school vacuum line switching.

The engine vacuum lines were spot on.

The Fix: Reading another thread suggested a separate vacuum pump for the HVAC vents. Starting at the vacuum tank (softball sized black ball) I traced the main feed back into the somewhere in the dashboard. It looked good. Then I did a slow inspection of the small hard plastic line coming off the vacuum tank. Yikes, the back half of the line was worn all the way through the line. I guess my prayers were answered in hopes that the problem was in the temperature controls in side of the dash board. A trip to the auto parts store found a length of vacuum hose that would fit, the now cut, ends of the outgoing vacuum line. The worn section was not visible to the eye. Only tracing with the finger tips found the bad section.
I also replaced the windshield wiper wash lines as they also rotted off at the front of the RV and inside the front compartment. I drilled out the through holes to 1/4in to allow a thicker walled line.

Starting the engine, the A/C clutch still not engage. However the defrost vent went into the correct mode for normal air flow. The R-134a fill is in the very front off to the left side near the air flow diverter. I pulsed the AC Pro R-134a bottle. I am not sure if my pulsing the freon refill or if the vacuum tank finally reached it operating condition, but I heard the A/C clutch engage. At that point, I did 10sec freon fill pulses and watch the low end pressure gauge start to come up toward the green. It took a while but I got the low end pressure gauge up to 7/8ths of the low markers before I ran out of refill. PTL, Inside the air was blowing cold air.

I did put in another order for a AC Pro R-134a refill bottle. I guess they do not come in the 20oz size. The order was for a 12oz refill which should put the low side pressure into the green zone.

Lessons learned is that I cover the front end of the RV with a heavy duty sacrificial tarp. They don't last long here but its better than replacing parts in the engine front compartment.

Things to do: I would very much like to put in a spring lift kit, especially in the rear. Over the years, the suspension has sagged a little. (Isn't that the theme for all of us over time?). We have a life time roof sprayed on, but the sides, front and back of the coach have taken a beating. I am not sure what the cost would be for a fresh paint job? I removed the old analog RCA TV from the front dash and am thinking of making a book/TV accessory shelf (lots of options there). Finally, the next thing that is going to be done is replacing the slide-out awning. All the items are neatly written into the Around-To-It list.

Best Regards, JohnF
AppliedThinking is offline   Reply With Quote

460, a/c, f53, ford, vacuum

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