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Old 08-27-2021, 08:26 PM   #1
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2014 Dash A/C performance on 450hp side radiator - Good?

We have been chasing a non-functioning dash AC system on our 2014 Allegro Bus 37AP. They rebuilt much of the AC system - evaporator core, compressor, dryer, valves. It works great at idle, but not going down the highway. Tech determined the head pressure goes over 300 after a while. Spraying the condenser with water gets the pressure back down. (Cleaned it first to be sure it wasn't just dirty.)

Tech thinks the condenser is plugged, but he asked one question I can't answer: did it EVER cool well? Since we just got the MH in 1/21, I just don't know if this was a design issue from day 1.

So, for anyone with a similar MH, does your dash AC work - no, ok, great?
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Old 08-27-2021, 08:29 PM   #2
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2014 Dash A/C performance on 450hp side radiator - Good?

Have you verified hot water is not flowing through the heater core? This is a known problem on some types of systems.

I would clamp one of the lines and give it a test. Or after a Highway run check the hoses. Should be cool and not hot up front.
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Old 08-27-2021, 08:59 PM   #3
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I have a 450 HP with side radiator and my a/c works fine. Are you sure the refrigerant charge is correct? If your system wasn't properly evacuated before it was charged, you could have non-condensables in it, air or dry nitrogen from leak checking is the most common when a good vacuum isn't pulled before recharging a system
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Old 08-28-2021, 08:11 AM   #4
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Before I took it back in, I verified both the fresh air (it's 95į outside) & heater core blend gates were working correctly by bypassing them. Heater core gate is a manual gate. Tech did the same tests (at my expense), and confirmed they were working correctly as well.

I thought it was low freon, but original work order stated 70 oz, based on system tag. Tech evacuated the system this time and confirmed it had 70 oz.

The fact that the condenser was clean, the head pressure was going up too high and dropped after he cooled the condenser, led him to the conclusion of a poor design or a clogged condenser.

Chuckftboy - thanks for confirming it isn't a design issue. I'll make sure they pull a good vacuum before they refill.
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Old 08-28-2021, 08:46 AM   #5
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70oz sounds like a lot of freon. Could your system be flooded with too much? My Denso tag says 2 lb's. My buddy's 2017 Phaeton is 2.5 lbs. Not sure how different your bus would be.
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Old 08-28-2021, 09:14 PM   #6
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The tag said 70oz. I heard some use as much as 88oz. Not sure why such a range.

I'll email Tiffin to confirm the tag is correct.
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Old 08-31-2021, 08:17 PM   #7
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FYI - Gary Harris from Tiffin stated our Bus has a capacity of 64 oz, but didn't think 70 oz would be too much to cause a problem.

I really like that a knowledgeable person responds to these types of questions from their customers!
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Old 08-31-2021, 08:33 PM   #8
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You have a condensing issue. There isn't enough air flowing across the condenser coil. It is either dirty and needs pressure washing or the fan isn't drawing enough air across it.
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Old 08-31-2021, 09:38 PM   #9
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70 oz for the charge sounds about right for a side radiator coach. The condenser being under the radiator makes for a very long liquid line.

On the other hand, a rear radiator coach has the condenser forward close to the axel with a much shorter liquid line.

If I remember correctly. 90 degree day, 1,200 RPM and about 225 lb head pressure is where mine was at.
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Old 08-31-2021, 10:11 PM   #10
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Quote:
Originally Posted by chuckftboy View Post
70 oz for the charge sounds about right for a side radiator coach. The condenser being under the radiator makes for a very long liquid line.

On the other hand, a rear radiator coach has the condenser forward close to the axel with a much shorter liquid line.

If I remember correctly. 90 degree day, 1,200 RPM and about 225 lb head pressure is where mine was at.
That would make sense. I did not realize the condenser was all the way back at the radiator. Yes, my condenser is up by the axle.

I hope the OP can get it resolved.
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Old 09-01-2021, 05:11 PM   #11
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The tech cleaned the condenser first thing when he saw the head pressure go over 300. Only spraying water on the condenser got the pressure down. Airflow is good.

They have/had it pressured to 300 and put dye in it just to be sure there isn't a leak. I'm still waiting for them to confirm the condenser is the issue, and give me a timeline & cost.
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Old 09-08-2021, 01:52 PM   #12
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They finally determined the cooling fan is cutting off at 900 rpm (as is normal), but it isn't turning back on when the AC is turned on. Manually locking the clutch verified the system cools well if the fan is going.

Does anyone know if there is a relay or sensor somewhere between the ECM and the cooling fan clutch?

One call to Tiffin stated the ECM may need to be reprogrammed but a second call stated no, the clutch needs to be replaced.

I've got another email into Tiffin, but trying to get this resolved this week. Thanks.

We know the clutch is not getting a signal to turn back on but we aren't sure if there is a faulty relay or sensor, or can the ECM be reprogrammed?
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Old 09-10-2021, 09:03 PM   #13
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You should have a fan relay controlled by the ECM but I have no idea where it is on your coach. Maybe a call to freightliner (800-385-4357) might help getting your mechanic pointed in the right direction.

I also checked the refrigerant charge for my coach (72 ounces). My lines are a bit longer so what Tiffin told you for your coach sounds correct. You were correct about a few ounces over probably would be fine as there is always a little loss when connecting and removing the gages.
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Old 09-10-2021, 09:36 PM   #14
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Call Bay Diesel & A/C in Red Bay, AL. They are THE service center for all things Tiffin A/C. The number is 256-356-8830 or 256-356-8803
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