wesnsue Report post Posted July 15, 2020 I have a 2015 36ft HR with a gas v10. When I drive up a hill (doesn’t have to be much) the fan on the dash quits & goes to the defrost. It doesn’t matter if it is outside are, AC, or heat. The Ford truck & RV center had it for 3 weeks & said it was an actuator. They said it was an RV problem. Then the RV repair (where I bought it) center replaced the actuator with no results. After 4 weeks in & out of there shop they gave up saying it is a Ford problem. The Ford truck center does not want to see me again. I now it is a vacuum problem but where? Where is the vacuum reservoir on a class A gas rig? Wes Share this post Link to post Share on other sites
huffypuff Report post Posted July 15, 2020 Vacuum leak, no reserve. Share this post Link to post Share on other sites
dickandlois Report post Posted July 15, 2020 Wes, Welcome to the FMCA Forum ! Totally agree that there is a vacuum issue. This Video might help find a hidden issue with a primary vacuum leak on V 10 engines. The fault codes listed also can come up, as the mileage on the engine increases . The Vacuum leak can cause converter failures down the line over time. Rich. Share this post Link to post Share on other sites
rls7201 Report post Posted July 15, 2020 Rich, I'm curious as to how a vacuum leak can cause converter failure on a Ford F53 V10 chassis. Thanks Richard Share this post Link to post Share on other sites
jleamont Report post Posted July 16, 2020 3 hours ago, RLS7201 said: Rich, I'm curious as to how a vacuum leak can cause converter failure on a Ford F53 V10 chassis. Thanks Richard It will lean out the engine causing it to miss fire, thus damaging the catalytic converters. That was a great question. Share this post Link to post Share on other sites
rls7201 Report post Posted July 16, 2020 18 hours ago, jleamont said: It will lean out the engine causing it to miss fire, thus damaging the catalytic converters. That was a great question. DUH! Brain fart on my part. I thought he meant torque converter. Share this post Link to post Share on other sites
jleamont Report post Posted July 16, 2020 2 minutes ago, RLS7201 said: DUH! Brain fart on my part. I thought he meant torque converter. LOL, I did at first also. Share this post Link to post Share on other sites
dickandlois Report post Posted July 16, 2020 My bad for not saying Catalytic Converter. I had only the engine in mind when I posted the Vacuum issue thoughts. Like, keep an eye on the one on the left-How fare left are you referring Sir? Rich. Share this post Link to post Share on other sites
kaypsmith Report post Posted July 17, 2020 My first thought was 12 volt to 120 converter, then I shook my head to clear that thought, LOL. Share this post Link to post Share on other sites
huffypuff Report post Posted July 17, 2020 Appears that OP got no help at all. Vacuum leak or check valve is first thought has nothing to do with spark plugs or Catalytic Converter. Please find where vacuum line comes through the firewall and trace to leak or check valve in both direction. Share this post Link to post Share on other sites
jleamont Report post Posted July 17, 2020 On most Ford products the problem is usually in one of these plugs. They are notorious for coming loose, another problem area is at the dash pots (actuators) those come loose also and leak. Locating these under the dash of an RV could be a difficult task. Share this post Link to post Share on other sites
dickandlois Report post Posted July 17, 2020 1 hour ago, jleamont said: On most Ford products the problem is usually in one of these plugs. They are notorious for coming loose, another problem area is at the dash pots (actuators) those come loose also and leak. Locating these under the dash of an RV could be a difficult task. Interesting thought Joe ! From the OP it sounds like things work with the AC / heat ducting vacuum switches, but the system defaults to the defrost mode only when the engine is under an increased load while going up a grade. I might be missing something ? Rich. Share this post Link to post Share on other sites
jleamont Report post Posted July 17, 2020 I have had them leak, not disconnect unless kicked which results in "stuck on defrost" complaint. Most times you can disconnect and reconnect and they stop leaking and it solves the loss of vacuum issue that is sounds like the OP has. Share this post Link to post Share on other sites
wildebill308 Report post Posted July 17, 2020 5 hours ago, DickandLois said: but the system defaults to the defrost mode only when the engine is under an increased load while going up a grade. I might be missing something ? I think defrost is the default any time it looses or doesn't have vacuum. Bill Share this post Link to post Share on other sites
f442485 Report post Posted July 18, 2020 If the a/c vents work normally under normal driving conditions, the leak could be anywhere. I would start looking for the vac reservoir and testing the vac signal in and out. I have had many reservoir tanks crack (plastic). just a thought Share this post Link to post Share on other sites
huffypuff Report post Posted July 18, 2020 There also should be a check valve to hold the vacuum to the HVAC system when accelerating. Even with a good check valve a leak can also be the source of failure. Share this post Link to post Share on other sites
dickandlois Report post Posted July 21, 2020 Think if you look at the video on my first reply on July 15th. the mechanic shows a bad spot in the Positive crankcase Vacuum line running between the intake manifold and the PCV located in the Valve cover. Not an uncommon issue with the V-10 series engine. Also the V-10 / Trident does not have a vacuum reserve tank. Big Gas power engines make allot of vacuum. The small 4 cylinder and 6 cylinder engines do not make a large source of vacuum. For a Trident to loose vacuum, there is a rather large leak or hole somewhere. Same goes for the 8.1 L V 8 engines. Rich. Share this post Link to post Share on other sites
