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Old 01-13-2013, 05:08 PM   #1
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More "DASH" A/C questions/concerns. Cold as it should be?

I've read a few old threads about the dashboard A/C on some RVs not blowing too cold, or not made to be too cold. And many drivers using the rooftop (coach) A/C units to cool the RV when on the road.

I tried to post to one, but it was too old. I wasn't allowed, so I started yet another.

I've got a couple quick questions before I go get gauges/manifold to check out my dash A/C.... Or call in the cavalry, to make sure I'm good and/or doing things right.

I've got a '99 Winniebago 35' (V10, Ford chassis).

It's about 65F outside (in the shade), and maybe 70-72 in the sun... and my vents on max AC are only blowing 58F at engine idle. If I bring the idle up to 2300rpm or so, and hold it for 2-3minutes... the AC at the vent will get down to 52.

If I go strictly to "vent", and high on the blower... it'll climb to 75+

Would this be a "normal" cooling capacity for my RV ya think?

I just dumped 2 cans of R134 from my local Autozone into the system thinking it would help (I know it's not always the "cure all" - but I had to try. And I know I should measure the high side, hence the need to get a gauge setup) and honestly, it didn't change much from my initial readings.

If you all tell me the 20 drop is "good", I'll simply get the gauges to check and make sure I'm okay. If you tell me it's "just okay", but could be better... I'll move onto the next step of asking my Ford tech for some help.

Thanks in advance!
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Old 01-13-2013, 06:00 PM   #2
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Well...
Per this post;
Dash heater and A/C controls, not operating correctly

I found a blue vacuum line that wasn't allowing my AC to go from "AC" to "MAX AC". Once I repaired it... I'm now down to 43.5F at the vent, with a tested ambient temp on "vent", at the vent... at 75

Not too bad from what I've been reading. Would you all agree?
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Old 01-13-2013, 06:25 PM   #3
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If you can see the AC compressor and get to the lines check the suction line and see if it is real cold. the suction line should be the bigger one of the two. Be careful and if there's not enough room to do it safely get a set of gauges to check pressures. Sounds like a low freon level or maybe the expansion valve could be stuck. I know what to check but hard to explain, hope this will help a little. Jim PS the engine needs to be running to check if line gets cold.
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Old 01-13-2013, 06:33 PM   #4
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I have had 5 motor homes and none of them have had a decent dash AC. Sounds like yours may be doing ok.
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Old 01-13-2013, 06:47 PM   #5
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The dash A/C is not designed to cool the whole coach. And just "dumping" in a couple of cans of R134a is dangerous. The units are designed to operate with a certain amount of refrigerant in the system. These are know as Critical Charged units...meaning that in order to work properly, they require a certain amount of R134a.

By over charging, you can damage the system as you can by running low on refrigerant charge. You need to understand the pressure temperature relation for the refrigerant and how the system operates to properly charge it.

Rather than spend the money on refrigerant and gauge sets, spend the money for a proper leak check, repair and recharge.

Ken
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Old 01-13-2013, 06:49 PM   #6
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Your heater control may not be closing the hot water from your radiator completely from the AC/Heater coils.
Use a pair of vise grips and clamp it on one of the heater hoses and see if cooling improves.
If it does than install a ball valve like some of us have done.
Just remember to open valve during winter months or wife may think its kind of cool during winter months.
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Old 01-13-2013, 07:20 PM   #7
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Quote:
Originally Posted by rvjimmy View Post
If you can see the AC compressor and get to the lines check the suction line and see if it is real cold. the suction line should be the bigger one of the two. Be careful and if there's not enough room to do it safely get a set of gauges to check pressures. Sounds like a low freon level or maybe the expansion valve could be stuck. I know what to check but hard to explain, hope this will help a little. Jim PS the engine needs to be running to check if line gets cold.
It's cold, and a bit of condensation is forming. Looks/feels normal to me.

And engine running... you serious? I mean... telling me that. Doesn't everyone know this?

Quote:
Originally Posted by bbeane View Post
I have had 5 motor homes and none of them have had a decent dash AC. Sounds like yours may be doing ok.
"Okay", as in... "could be better"? Or... okay, as in... it's fine, don't mess with it.

Quote:
Originally Posted by TXiceman View Post
The dash A/C is not designed to cool the whole coach. And just "dumping" in a couple of cans of R134a is dangerous. The units are designed to operate with a certain amount of refrigerant in the system. These are know as Critical Charged units...meaning that in order to work properly, they require a certain amount of R134a.

By over charging, you can damage the system as you can by running low on refrigerant charge. You need to understand the pressure temperature relation for the refrigerant and how the system operates to properly charge it.

Rather than spend the money on refrigerant and gauge sets, spend the money for a proper leak check, repair and recharge.

Ken
Understood. And anyone who thinks the dash A/C should cool the RV is ... nuts. It'd take forever unless the outside air was colder then inside.

And also why I said... "I know... I know..." about the 2 can dump. I know it's risks and possible causes... A risk I was willing to take I guess. Sometimes, learning the hard way... is the only way for me.

I wasn't going to spend any money on a gauge set. I was going to borrow it from a Ford tech friend of mine who offered.

Quote:
Originally Posted by 007 View Post
Your heater control may not be closing the hot water from your radiator completely from the AC/Heater coils.
Use a pair of vise grips and clamp it on one of the heater hoses and see if cooling improves.
If it does than install a ball valve like some of us have done.
Just remember to open valve during winter months or wife may think its kind of cool during winter months.
I've heard of this valve (and the ball valve mod to correct the problem)... but wouldn't know which line to pinch off.
... have a picture (as example)?
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Old 01-13-2013, 07:23 PM   #8
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AND... to all that have responded... THANK YOU... however, ALL BUT ONE didn't answer my question about the amount of degrees it's cooling down, and if it seems okay. I've read lots and lots of forums about the ball valve mod, or how people shouldn't rely on the dash A/C to cool the RV...etc.etc. I'm just looking to see if my pull down percentage should be greater. Or if it seems normal and what most other RV owners have experienced.

So...

Measuring at the vent, with digital thermometer

FROM - 75 (knob on "vent")
TO - 43.5 (knob on "max ac")

That is good, great, or ???
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Old 01-13-2013, 07:23 PM   #9
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Also, if it is tool cold it won't work either.

There is a valve that controls the release of liquid into the evaporator, reason is to keep it from icing up, if ambient air us too cool the valve will sense this and reduce the output.

You tossed in gas, that is a bad thing, higher temperature will mean higher pressure, so DO GET THE MANIFOLD ON IT!

There is a chart that will tell you the correct pressure for ambient temperature, your system may be okay bring overfilled now, this summer maybe not.

The 20 degree rule applies to most all air conditioning units under one condition, they need to be operating under normal operating conditions.

Sorry it came out that way but it sounds good.

What it means is the AC is usually used in the summer when it is warm. So it will cool the warm air the 15 to 20 degrees inside and pump it to the 90 degree outside.

It is not designed like a wine cooler that cools cold air
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Old 01-13-2013, 07:28 PM   #10
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Originally Posted by TQ60 View Post
Also, if it is tool cold it won't work either.

There is a valve that controls the release of liquid into the evaporator, reason is to keep it from icing up, if ambient air us too cool the valve will sense this and reduce the output.

You tossed in gas, that is a bad thing, higher temperature will mean higher pressure, so DO GET THE MANIFOLD ON IT!

There is a chart that will tell you the correct pressure for ambient temperature, your system may be okay bring overfilled now, this summer maybe not.

The 20 degree rule applies to most all air conditioning units under one condition, they need to be operating under normal operating conditions.

Sorry it came out that way but it sounds good.

What it means is the AC is usually used in the summer when it is warm. So it will cool the warm air the 15 to 20 degrees inside and pump it to the 90 degree outside.

It is not designed like a wine cooler that cools cold air
Got'cha... Will do!!
I'll have the manifold on it sometime this next week. If not me ... the Ford Tech will be making sure I didn't foul things up.
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Old 01-13-2013, 07:41 PM   #11
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This picture is in the link provided:


It does not matter which hose you use. This would improve you cold reading.
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Old 01-13-2013, 08:01 PM   #12
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This picture is in the link provided:


It does not matter which hose you use. This would improve you cold reading.
Excellent...! Thank you.

Now, for the dumb(er) question; Where should I be looking (it's dark out now, and I'll have to do so tomorrow)? In the doghouse area (engine), or under the hood (front of coach)? I'll look for the evans valve in your picture first (not sure my coach has that brand). But more insight to where I'm looking would be great!

... I've got the rear heat too. So I know there's two water lines running to the back (had to re-zip tie them today as they were rubbing on hose clamps). Lots of hoses... and I want to be sure I am doing the right one!!

EDIT: Found some threads on the subject to give me better pictures/insight;
Maximizing dash air

I also don't think I have the evans system. I think it's Frigitte (or however you spell it)
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Old 01-13-2013, 09:17 PM   #13
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You just need to find one heater hose to the dash AC/Heater box under your hood up front.
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Old 01-13-2013, 09:36 PM   #14
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You just need to find one heater hose to the dash AC/Heater box under your hood up front.
Got it...
I'll look for them tomorrow. And, I'd like to find the "valve" and see if it's operating properly too.
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