Seeking Additional Help On Dash HVAC Problem - Page 2

l1v3fr33ord1 · 02-02-2021, 05:47 PM

LeeB-

I'm glad you got it fixed! And, I was happy to help.

imnprsd · 02-02-2021, 09:21 PM

Absolutely! Thanks for letting us know the wires to the back of the Control Board can wiggle loose over time! ...And it did not cost you anything or big bucks and time to take the RV to the shop. So a little encouragement goes a long way.

...Pat yourself on the back too!

...And now you know how a basic relay works!

Speaking of relays, you should hear a beep when you connect Pins 85 to 86 on that old relay, because a coil (wire) is connecting the pins. If you do not hear a beep the coil is bad.

So on one hand you found a loose connection at the control board, and on the other hand you have a "open" or burned coil on that old relay. Hmmm.... there is more correlation going on, but who cares if everything works!

* The heater should always work in any temperature.

* What caused your vacuum line to open? Mice? ...Vibration/chaffing?

* If your AC is not turning on in sub-70F weather, let us know if it starts working when you put a hot towel on top of the TXV. IDK. I've never tried it, but I think it should.

* That binary switch next to your TXV sends power to you compressor.

I do not know if this connection (NC) goes to the control board first or not, but I do know if you connect the two wires with a fuse (or wire jumper) it will turn your compressor on and off as you unplug the jumper. So with the jumper you are taking the binary switch out of the circuit.

==> Using a fuse is a good jumper, and if the male-female ends are compatible it's perfect to use. And you can unplug the fuse easily.

==> You know the binary is bad if the compressor does not turn on "as-is" but will run if you add a jumper to bypass the binary switch.

imnprsd · 02-02-2021, 10:42 PM

When you are diagnosing a problem or fixing a "bug" you should trying one thing at a time and then see if it has a positive affect.

For example: Did you first change that external relay and then see if your fan controls work?

...Or did you also fiddle with that loose plug and and change the relay... and then see if your fan controls work? ...Which would be doing 2 things at once.

And according to the wire colors in the schematic they seem to match your external relay wire colors on the fire wall. Is this correct? If so this is the "High Blower" Connector Relay.

Notice this relay DOES utilize Pin 87a. (See relay diagrams above.) And 87A is NC, but then "opens" when the coil is energized by the trigger on 85 or 86. ...Most relays do NOT use the 87pin at all, but apparently this system does. So that's kind of cool.

Note: A "trigger" is the switch you throw and you can switch the positive or switch the negative. The goal is to complete the circuit so the trigger passes +12V through the coil... that causes the relay to work as you wired it. That usually means this: "Whatever you put on Pin-30 goes out Pin-87."

...And when you turn on the coil... pin 87 turns off.

...And as just explained, when you turn on the coil the higher voltage on Pin-30 is now connected to Pin-87.

So if it's not too much trouble, can you fill in this relay chart:

PINS COLORS FOR HIGH BLOWER RELAY

85 -
86 -
87a -
30 -
87 -

LeeB · 02-03-2021, 10:31 PM

Aswers

Quote:

Originally Posted by imnprsd

What got me to look at the relay first was you identifying it in the picture. I was looking at my work bench and noticed I had one from when I installed NEW fog lights. I did not have to use it. So I thought what the heck I'll replace the one on the MH. The Fog Light relay only had 4 pins and the one on the MH had 5 so I bought a new and installed it.

Speaking of relays, you should hear a beep when you connect Pins 85 to 86 on that old relay, because a coil (wire) is connecting the pins. If you do not hear a beep the coil is bad. I tested the old one going from 85 86 and heard NO beep... So I GUESS it was bad and I lucked out...

So on one hand you found a loose connection at the control board, and on the other hand you have a "open" or burned coil on that old relay. Hmmm.... there is more correlation going on, but who cares if everything works!

* The heater should always work in any temperature.

* What caused your vacuum line to open? Mice? ...Vibration/chaffing? I have no idea what happened to it or why. The only thing I can think of is. Kind of a long story but the MH sat idle for around 5yrs and that green vacuum line crumbled as soon as I touched it. At the time I had no idea what it did I do now. It is on my list to repair.

* If your AC is not turning on in sub-70F weather, let us know if it starts working when you put a hot towel on top of the TXV. IDK. I've never tried it, but I think it should.I'll try it and see what happens

* That binary switch next to your TXV sends power to you compressor.

I do not know if this connection (NC) goes to the control board first or not, but I do know if you connect the two wires with a fuse (or wire jumper) it will turn your compressor on and off as you unplug the jumper. So with the jumper you are taking the binary switch out of the circuit.Got ya

==> Using a fuse is a good jumper, and if the male-female ends are compatible it's perfect to use. And you can unplug the fuse easily.

==> You know the binary is bad if the compressor does not turn on "as-is" but will run if you add a jumper to bypass the binary switch.

imnprsd · 02-04-2021, 10:13 PM

So it sounds like you replaced the 5-Pin High Blower Control Relay in the schematic above and that was the root cause of your AC control board problems. What do you think?

I arrive at this conclusion, because you said your old 5-Pin relay will not "beep" in continuity mode on the Voltmeter between pins 85 and 86. This implies you have a bad High Blower Control Relay.

REGARDING RELAY TYPES: A common "Bosch" relay comes as either a 4 or 5-pin type. It's the female socket that often is the limiting factor... and most relays do not use the 87a pin even if it's available. But if you have 5-wires you need a 5-pin male relay... as you do in this case.

Note: If you have a 5-pin relay and you want to use it with a 4-pin relay female, you can cut off the male Pin 87a if it's not uses. So the "footprint" is just as relevant as the function when dealing with relays.

The relay is a remarkable, simple powerful device that changed circuit design. And when you combine relays it gets even more interesting.

...So did you find a loose wire to the control board or was it disconnected? I'm a little fuzzy on that part in your story?

Glad your system is working. Please keep us posted on how strong your AC is blowing cold. At 93F the lowest temperature I got out of my dash was 49F. That's a -44F difference; and at 103F the your AC system should lower the vent temperature by -45F which equals 58F out the vents.

...Most RV'ers have be operating on much less performance, because they do not know how to overhaul their system. So if you find you do not get at least -44F out of your vents, with average humidity, then you may want to evacuate your system; recharge it with the specified amount of 134A (+10% IMO); and you may try replacing your Receiver Dryer and TXV.

TIP: Try to get all that old PAC100 oil out of your system too! ...And replace with PAC100 with ICE Additive!!! If you want to know how to do this yourself, then search for my threads on www.IRV2.com.

This also explains why your AC system will not turn on at sub 75F temperatures, because you A) Usually do not need AC when in the 70's; and B) turning on your system in 70F weather would freeze over your evaporator if the system is designed to lower temperatures by -42 to -45F in any weather.

Indy Bob · 02-05-2021, 12:00 PM

Here we go. THIS MAY HELP
2000 Ultimate Advantage has no cold air from the dash unit. The 3 knob control was suspect. There were 4 clicks of fan speeds. The ones that worked were the 1st and 3rd. 2nd and 4th (high) to not do anything. Went to a shop where they talked about this.
* the 2 fans in the rear driver side, near the engine, did no run. They are similar to the ones in cars. They need to run to cool the fins for cold air.
The guy says he is going to do something that won't hurt a thing.engine running, controls on high. Nothing coming out. He throws a pale of water on the fans and fins.
TWO SECONDS LATER THE DASH VENTS BLOW PAPERS OFF THE PASSENGER SEAT. I CLICK THE FAN AND ALL 4 SPEEDS REACT. ICE COLD AIR BLOWING OUT
The fans did not work when control was turned on. Further exam
UNBELIEVABLE. The main power harness with 2 wires that go to connections to both fans were CUT OFF. DID a quick power wire test to the exiting wires from both fans. Turned on switch, fans started
Hope the water splash gives you an idea. I did buy a used control from Colaw in Missouri.
Last thing. The large plastic box under front hood to the left (blank brain right now) it has antifreeze running through it. There is a small item with a curled spring that goes in the back side with 2 screws.
I replaced that too. Working great.

CAN YOU BELIEVE SOMEONE GOT UNDER THERE AND CUT MY WIRING OFF FOR THEIR RIG.

LeeB · 02-09-2021, 06:23 PM

UpDate.... The picture is a little blurry but it looks like our HVAC is fixed...... Huge thanks to all that contributed...... Especially a few and you know who you are...... Time to move on to my next project......
Thanks again LeeB

imnprsd · 02-09-2021, 07:53 PM

That's fantastic!

For the price of a relay you are back in business!

When you OAT is in the 60's you will not see more than -20F drop because the system is protecting itself from freezing the evaporator. That's why you only show 40F out the vents, but it's enough to know the AC system is working!

Please send us another picture of your vent temp vs. OAT after it heats up to 85+F; and if you are not seeing a -42F to -45F temperature drop we can suggest ways to deal with that.

You AC will work optimally between 85F-103F, but after that efficiencies drop off.

LeeB · 02-09-2021, 08:01 PM

Quote:

Originally Posted by imnprsd

That's fantastic!

For the price of a relay you are back in business!

Please send us another picture of your vent temp vs. OAT after it heats up to 85+F; and if you are not seeing a -42F to -45F temperature drop we can suggest ways to deal with that.

You AC will work optimally between 85F-103F, but after that efficiencies drop off.

Yes I was pretty happy. I will say this that I did get a small drip of water coming from one of the hoses but a quick tighten of the clamp stopped it. (Remember the coach sat for a few years and I was not really surprised)
Thanks again LeeB

pablonebrot · 02-19-2021, 06:14 AM

I decided to create my own list of reasons - why an HVAC does not turn on. Here are, in fact, 3 items on this list:

The button for turning on HVAC does not work or the wires from the compressor are disconnected.
The fuse is blown (the simplest thing that can be).
There is not enough refrigerant in the system.

Every RV has its own electrical weaknesses, which over time start to cause problems. It can be either poor-quality soldering of an HVAC control unit or unreliable wires/connectors that are constantly torn or disconnected.

Using an HVAC start button, we do not turn on it directly, like a conventional switch, but give a request to an engine control unit (ECU) to turn on an air conditioner or heating. If the button and its circuit have problems, then a control unit, of course, will not receive the activation task.

Check the button (with a multimeter) and electrical connectors on a compressor. And this, unfortunately, is all that you can do on your own. Since, if the circuit is working and the ECU received a request to turn on an air conditioner, this does not mean that it will satisfy your request.

If there is a lack of refrigerant in a system, the ECU will definitely not start a compressor. And this means that you need to contact a technician who will diagnose and fill an HVAC.

Moreover, this information might be useful, too!

Journey cat · 08-09-2021, 10:23 AM

I thought I’d ask here Would anyone know where the dash A/C dryer is located on a 2005 Winnebago 34H Freighter chassis Could it be located inside this black box ?