Front AC not blowing as cold as rear AC?

[rayza]

I have 2 Dometic 13.5

I have a thermapen, and I used it to measure the air coming out of the ceiling vents. The front AC is putting out 62 degrees in the front, and 77 degrees on the rear most vent.

The rear AC (2nd zone) is putting out 55 degrees in the front most vent, and 52 degrees in the rear most vent.

Is this normal? Is this something I should get looked at?

["007"]

Are you using AC's one at a time or both working together?
Your ceiling ducks, one is cool air other is the return air, go front to back full length. of coach'
Both AC's set at same temperature?
Have to realize front return is sucking hot air off windshield possibly.

[rayza]

Originally Posted by "007"

Are you using AC's one at a time or both working together?
Your ceiling ducks, one is cool air other is the return air, go front to back full length. of coach'
Both AC's set at same temperature?
Have to realize front return is sucking hot air off windshield possibly.

Both working together. I am testing now by turning off zone 2 and waiting 15 minutes to see what temperature is coming out of the front.

Both ACs are set the same (70 degrees).

Both AC's have been set at 70 for more than 24 hours, so it (should) be keeping it fairly consistent, but the inside temp in the front is 78 degrees. The back of the RV is 70-71 degrees.

[DGBPokes]

Don’t know the specifics of your rig, but in ours there is a definite temperature imbalance from the front to the back.
1. There is a LOT of heat comes in from the windshield, and the windows, and the door, and the exhaust fan, and the microwave vent. Not found in the bedroom.
2. The thermostat for the front is mid coach, the temp sensor in the bedroom is in the corner, of the bedroom.
3. The rear A/C dumps air directly on to the thermostat-mid coach. So the hot air builds in the front of the coach and the front AC doesn’t come on to deal with it since the rear AC is dumping cold air on the thermostat. And the rear AC runs all the time trying to keep up with the overall temp.

What I have done to help balance the system.
1. Added extra filters in the rear outlets to move more rear air to the front
2. Place aluminum foil in the outlet dumping on the thermostat
3. Wife hates it, but I take a paper pamphlet and insert it over the top of the thermostat to again shield it
4. Set the front AC temp 2 degrees lower than the rear temp.

If you don’t have an IR temp fun ( $20 Harbor Freight ) fun thing to have. One hot summer day in W Texas 104* The temp of the frame around the window, on the INSIDE was 140* That’s a lot of heat add.

[rayza]

Originally Posted by DGBPokes

Don’t know the specifics of your rig, but in ours there is a definite temperature imbalance from the front to the back.
1. There is a LOT of heat comes in from the windshield, and the windows, and the door, and the exhaust fan, and the microwave vent. Not found in the bedroom.
2. The thermostat for the front is mid coach, the temp sensor in the bedroom is in the corner, of the bedroom.
3. The rear A/C dumps air directly on to the thermostat-mid coach. So the hot air builds in the front of the coach and the front AC doesn’t come on to deal with it since the rear AC is dumping cold air on the thermostat. And the rear AC runs all the time trying to keep up with the overall temp.

What I have done to help balance the system.
1. Added extra filters in the rear outlets to move more rear air to the front
2. Place aluminum foil in the outlet dumping on the thermostat
3. Wife hates it, but I take a paper pamphlet and insert it over the top of the thermostat to again shield it
4. Set the front AC temp 2 degrees lower than the rear temp.

If you don’t have an IR temp fun ( $20 Harbor Freight ) fun thing to have. One hot summer day in W Texas 104* The temp of the frame around the window, on the INSIDE was 140* That’s a lot of heat add.

Thanks, I think my sensors are fine, they are far enough away that it shouldn't be an issue. The front AC sensor is in the slide out where the sofa is and it is usually a little warmer there. The bedroom AC is on the wall and no vent is pointed at it.

I did try putting foil in one of the bedroom vents that blows on my wife. She doesn't like it so cold at night so this works out well. I also put one in the bathroom because that room I always have the vent running and it is usually 5 degrees colder than the rest of the RV. I'll see if this helps tomorrow.

I'm also getting Magneshades in 9 days so super excited about that!

[Craig36]

Although I have never measured the exact temps, I have the same issue with my 2007 KSDP. The front AC ducts have to move the air much further, so it makes sense that the air has heated somewhat by the time it hits the front outlets.

That being said...I have often wondered if the front (original) AC unit puts out air as cold as the rear one which I recently replaced.

Last week when it was 102 outside in Salt Lake, the coolest I could get the front area was 85 degrees. Fortunately we sleep in the back where it got nice and cold!

[bruceisla]

You should measure the Delta (the difference) between the warm air inlet and the cool air outlet for both units independently. Holding a bath tissue near the vent will help you identify which vent is inlet vs. outlet. For each A/C unit, the Delta should be 20 degrees (approx). For instance, 90 degrees in should yield 70 degrees out.

[millerj]

On my 2012 43' Ventana one of the three ac's went out when it was less than a year old and had to be replaced. My understanding is there should be a 20-22 degree difference between the temperature of the air between the air intake vent and the output vent. At least that's what I have read.

[rayza]

I put foil on 2 of the vents in the back AC. One in the bedroom, and one in the bathroom (as the bathroom is usually frigid).

I can't really say today how well it helped out as the temperature is now 10 degrees cooler. Will have to see when it gets back into the 90s.