Stuck In Defrost Mode

[Duke 48]

My Problem: The heater/ac system on my 2004 Hurricane is stuck in defrost. Research and troubleshooting to this point has led me to believe the problem is in the pneumatic vent control circuit.

Now I need to physically locate the vacuum pump, the reservoir, and the fuse box ( & fuse # ) supplying power to the vacuum pump. Plus, a circuit diagram would be very helpful.

All input is appreciated.

[16ACE27]

Vacuum pump? It's not a diesel, gassers use engine vacuum.

[Duke 48]

Originally Posted by 16ACE27

Vacuum pump? It's not a diesel, gassers use engine vacuum.

Obviously showing my ignorance.

But happy to hear I wont be replacing a vacuum pump.

The engine is a Ford V-10. Should I expect the engine / vacuum connection be similar on most ford trucks of that age?

[16ACE27]

Originally Posted by Duke 48

Obviously showing my ignorance.

But happy to hear I wont be replacing a vacuum pump.

The engine is a Ford V-10. Should I expect the engine / vacuum connection be similar on most ford trucks of that age?

The connection has been the same for decades on all vehicles. The difference is in the details of your HVAC system in that RV. Most Thor Class A RVs have used EVANS TEMPCON systems so that may be a place to start once you determine why/where your vacuum is lost.

[OldWEB]

Many people discuss deteriorated vacuum hoses and then the system defaults to defrost mode.


Good luck

[blw2]

I just went through this a few weeks ago in my E-450 chassis class c. Watched several youtube tutorials, and cobbled together my own version... basically find and cut the hose where it passes through the firewall. install a new accumulator (purchased from amazon) and a new check valve T fitting I had to get from the Ford dealer. Abandoned the old tank and check valve where it is, buried under much stuff....what I understand to be many hours worth of labor to get to...
Stupid design but easy and relatively short fix...not counting the research time.
Mine was easy because it's just like every econoline van. I suppose yours being a class A things will be in different places so you'll have to do some more investigation and tracing...
good luck!

[Lt Keefer]

I had that happen on my last coach. The culprit was rodent damage. Critters had chewed a number of vacuum hoses under the dash. It was quite the effort to repair.

[Duke 48]

I really do appreciate all the information everyone is provided to this point. It has been very helpful.

For me, the challenge is now to access and identify the components, and connection points needed to actually do the line trace and troubleshooting. It is going to be a couple of days before I can get back into this. But, I will keep posting my findings.

[Duke 48]

Think this sphere, attached to the firewall on the passenger side, in the engine compartment, is the vacuum accumulator. Can anyone confirm this for me.

[grizzlyclaus]

Yes that is the vacuum reservoir.

[Duke 48]

UPDATE:

I finally found the vacuum line leak. It was a dry rotted connector between the vacuum line and the vacuum reservoir. Unless there are other problems that I haven't found, it should be easy to replace the connector, and get the system back in order.

I do want to express my appreciation for all those that have helped me troubleshooting this vacuum line leak.