Community Forums

jfguay2 · 03-12-2018, 08:41 AM

Hello,

Upon my recent trip to Florida, I noticed that my Ford E450 blower heater would temporarily turn off when going up a hill. I had the blower to push through the vents, and when it would come back , it would start by blowing on the feet for a second to then go back to vent . Is this normal ?

JIMBO34PA · 03-12-2018, 09:02 AM

you have a vacuum leak in the hvac or engine . The hvac defaults to blow air on windshield with no vacuum . The blower doesnt stop just the airflow out vents switches to windshield . There is a reservoir can that holds vacuum for accell up hill (low vacuuum situations) , but if a hose to one of the vacuum motors or there is a split in hose it will default uphill to windshield . Check on passenger side under dash sometimes the white stripe hose gets knocked off the vacuum actuator motor by foot. Sometimes the check valve is defective too. jim

TonyMac · 03-12-2018, 09:06 AM

What you might be seeing is a loss of vacuum due to wide open throttle (wot). If your hvac distribution is run by vacuum -- not uncommon at all -- and your vacuum depletes due to prolonged wot, your hvac distribution will resolve to its emergency vacuum lost distribution which is defog. You could have a vacuum leak as well, might wanna check for that. Once you terminate wot, the system will build vacuum and begin normal hvac distribution.

TonyMac · 03-12-2018, 09:09 AM

Redneck check for vacuum leak:
1. Get a beer or 12
2. Get some starter fluid.
3. Start engine
4. Drink beer
5. Spray starter fluid on vacuum items in the engine bay. The engine will rev slightly when you spray the leaking component.

Waiter21 · 03-12-2018, 12:41 PM

Quote:

Upon my recent trip to Florida, I noticed that my Ford E450 blower heater would temporarily turn off when going up a hill.

The systems are designed so that if the vacumn fails, it should revert back to the defrost mode.

I suspect your blower isn't failing. When you mash down on the gass with full throttle, you're producing little vacuum, and the heater mix doors are going to the defrost mode.

As other mentioned, you may have a vacuum leak that's aggravating this

spyderRV · 03-13-2018, 02:57 AM

The typical vacuum system has a one way valve to lock in the vacuum in a canister when there is no vacuum. So it could be a leak in the system or the valve could be bad.

jfguay2 · 05-27-2018, 03:40 PM

Ok so I finally resorted to bypassing the oem vacuum reservoir and check valve by connecting the vacuum line that is hooked to the intake directly to the hvac distribution module. Now it seems that i am getting the default switch to defrost even more often which would indicate that th vacuum reservoir is indeed needed ( i did not add one back and have yet to add a check valve as well. What is a good replacement option for a 2008 Ford e450? I am not finding much on amazon...

JIMBO34PA · 05-28-2018, 08:38 AM

Find the leak, it defaults faster now because the reservoir added capacity is gone . Very common is the hose gets kicked off the outside air door vacuum motor (white stripe hose) in passenger side foot well .

jfguay2 · 05-28-2018, 07:14 PM

Hey I Finally got a Dorman vacuum reservoir 47 076 , which has a check valve .

Installed it in my bypass circuit and gave it a try. Once the vacuum was going I disconnected the intake and still it kept the vacuum and the head did not got to defrost ! YES !

Thank you all for helping out ! Name: vaccum%20tank.jpeg
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Name: vaccum%20tank.jpeg
Views: 471
Size: 8.9 KB

wa8yxm · 05-29-2018, 06:04 PM

You have a vacuum leak more than likely as this should NOT happen

If yoru rig is a gasser when you open the throttle all the way there is not a whole lot of manifold vacuum. So the defroster is the DEFAULT for the HEVAC system (you may find it is blowing on the windshield if yoru co-pilot wishes to check)

Every time this has happned to me I had a vacuum leak in the ssytem, Assorted vehicles. never my RV though.

jfguay2 · 05-29-2018, 06:14 PM

Quote:

Originally Posted by wa8yxm

You have a vacuum leak more than likely as this should NOT happen

If yoru rig is a gasser when you open the throttle all the way there is not a whole lot of manifold vacuum. So the defroster is the DEFAULT for the HEVAC system (you may find it is blowing on the windshield if yoru co-pilot wishes to check)

Every time this has happned to me I had a vacuum leak in the ssytem, Assorted vehicles. never my RV though.

Do you mean to say that even though i may have had a leak in the check valve of the hvac vacuum line , that the manifold vacuum should still not have gone so low even while accelerating and going up hill ?

DryCreek · 05-29-2018, 09:40 PM

Quote:

Originally Posted by jfguay2

Do you mean to say that even though i may have had a leak in the check valve of the hvac vacuum line , that the manifold vacuum should still not have gone so low even while accelerating and going up hill ?

Possibly so, or maybe....
I think that that post may have missed the part where you added the vacuum reservoir back in the mix. But, while you're at it - check the large hose coming from behind the throttle body and going up to the vapor cannister purge valve. That hose on my Class A had gotten rubbed pretty thin from the doghouse cover. I would suspect that on the Class C chassis the same is possible. Have you ever gotten the oxygen sensor stuck lean code in that cleared and only came back after prolonged idling? That is a clue to a vacuum leak.