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I'm back, AC not freezing up


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jjrbus
User

Aug 17, 2017, 1:17 PM

Post #1 of 29 (508 views)
I'm back, AC not freezing up Sign In

93Toyota RV, Toyota pickup. Converted 2 years ago with the help of this forum to 134a. Recently evaporator started freezing up and I got started in wrong direction.

Got system put back together and recharged with 17oz of 134a and had 50° dash temp at 87° ambient. So 37 degree drop.

Since doing recharge I found info that I used 20 oz 134a last time and had dash temp of 41°

Took for 60 mi round trip and couple trips to store and not freezing up. Have ambient temp of 92° and dash temp of 58° so 34 degree drop.

No sign of refrigerant leak and not freezing up. I'm assuming it is not getting cold enough to freeze?

Compressor does not seem to be cycling on and off, I have no idea how often it should cycle and no way to tell when I am driving.

Should I put a bit more 134a in, or look for something else?


Hammer Time
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Aug 17, 2017, 4:18 PM

Post #2 of 29 (500 views)
Re: I'm back, AC not freezing up Sign In

That is not a cycling system so it will only cycle if there is an issue.

Let it go and see how it acts now.



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Sidom
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Aug 17, 2017, 5:42 PM

Post #3 of 29 (492 views)
Re: I'm back, AC not freezing up Sign In

The 41 sounds a little more in line to what I would expect to see from a Toyota, they have pretty good systems on them..

50 & 58 sound too high for this system....

I realize you were just drive around and don't have high & low side pressures...






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jjrbus
User

Aug 17, 2017, 6:10 PM

Post #4 of 29 (484 views)
Re: I'm back, AC not freezing up Sign In

Thanks for the responses, glad to hear it is not a cycling system, I thought something was wrong!

This is what I had when I charged it last week Sat. Ambient temperature was 87° with 67% humidity. I had a lo pressure of 30 and a high of 160 with a dash vent temperature of 50°, which is 37° under ambient.

Tom indicated I should not try and fill the system all at once and drive a bit to let it balance out. When I was charging I could not find the info that I had added 20 oz 2 years ago with a vent temp of 41, so stopped at 17 oz and 50° dash temp.

Should I check pressure again?


(This post was edited by jjrbus on Aug 17, 2017, 6:14 PM)


Sidom
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Aug 17, 2017, 8:48 PM

Post #5 of 29 (471 views)
Re: I'm back, AC not freezing up Sign In

Sometimes too many chef's spoil the broth.......

It sounds like HT and Tom got you up and going and that thread was so long I only read bits and pieces so I'm not sure on everything that has been done....

but at 87 ambient I would expect the high side to be at or over 200, 160 is way low...






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Discretesignals
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Aug 18, 2017, 5:22 AM

Post #6 of 29 (452 views)
Re: I'm back, AC not freezing up Sign In

Don't think that 17 oz is enough refrigerant.

The capacity of that truck with r-12 was 28.8 oz. 80% of 28.8oz is 23.04 oz of R-134A.

Are you running the AC is recirculation mode. Also there is a hot water valve that should be closed when the heater isn't on.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Aug 18, 2017, 5:25 AM)


Tom Greenleaf
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Aug 18, 2017, 6:01 AM

Post #7 of 29 (443 views)
Re: I'm back, AC not freezing up Sign In

Ditto: Charts can be wrong but I show 29oz was OE for R-12 X .80% max is 23.2. That's within "close enough." I've said found many will like less than 80% none wanted more for me,
T



jjrbus
User

Aug 18, 2017, 7:26 AM

Post #8 of 29 (433 views)
Re: I'm back, AC not freezing up Sign In

Thanks for all the responses!

I am running in re-circulation mode (outside air shut off) and when I use AC I keep the Cabin part of the RV separated from the truck part.

You did tell me to try clamping off the heater hose to make sure hot water was not circulating in heater core and of course I neglected to do it.

My Factory service manual shows Specified amount: 700 – 800 g (1.5 – 1.8 Ib) for R 12. Which according to the online converter would be 24.69 to 28.21 oz R 12. Starting at 65% would be 16.4 to 18.33 of 134a and 80% would be from 19.75 to 22.56 oz 134a. Those are the numbers I have been using.

I will add a bit of 134a and report back.


Hammer Time
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Aug 18, 2017, 12:19 PM

Post #9 of 29 (401 views)
Re: I'm back, AC not freezing up Sign In

I really don't understand why you are still looking for problems. You have cold air. You no longer have a freezing problem and yet you are still looking for ways to make it colder.........................why?

Do you want the freezing problem back or do you just enjoy breaking and then fixing things?



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



jjrbus
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Aug 19, 2017, 8:41 AM

Post #10 of 29 (363 views)
Re: I'm back, AC not freezing up Sign In

Now I am confused again. You are saying I should stay with 50° vent temp and 17 oz 134a?

When I originally did this in 2015 I followed Toms instructions http://www.rverscorner.com/indiana.html post #24 and got 41° with 20 oz 134a and it worked fine for over a year till the evaporator started freezing up.


Hammer Time
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Aug 19, 2017, 8:52 AM

Post #11 of 29 (361 views)
Re: I'm back, AC not freezing up Sign In

You have cold air................ It's not freezing

What is the problem?

You should NEVER see 41 degrees out the vent. That is too cold and on the way to freezing.

You are supposed to be checking this out the center vent on high blower. 50 to 55 degrees at idle on a hot day is ideal.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
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Aug 19, 2017, 5:21 PM

Post #12 of 29 (342 views)
Re: I'm back, AC not freezing up Sign In

jj - What I've said in 2015 on some post isn't your car now but applies to how much refrigerant to add when not able to be absolutely sure how much is perfect. Unknowns with a retrofit many reasons get involved. Starting at 65% is prudent and work up till pressures and performance match temps and RPMs within ranges considered normal.


Ha - what is normal? You tell me. Humidity matters - bugs or dirt, fan(s) effectiveness - a whole novel of details. If performing best not to get greedy as little as an ounce too much you just lose all efficiency and system works way too hard. Much more you cause damage or choke compressors most would just screech the belt if lucky or ruin the compressor. That's why,


Tom



Sidom
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Aug 21, 2017, 9:19 AM

Post #13 of 29 (300 views)
Re: I'm back, AC not freezing up Sign In

Do everything the way you have been doing it but put the blower speed on low and see what temp you get?






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Hammer Time
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Aug 21, 2017, 10:08 AM

Post #14 of 29 (294 views)
Re: I'm back, AC not freezing up Sign In


Quote
Do everything the way you have been doing it but put the blower speed on low and see what temp you get?


Are you trying to force it to freeze?



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Sidom
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Aug 21, 2017, 11:55 AM

Post #15 of 29 (286 views)
Re: I'm back, AC not freezing up Sign In

Not at all... If everything is working correctly, it won't freeze on low, that is the purpose of the temp senor or capillary tube whatever is used...

You get your coldest temps on the low speed...

He stated he was getting 50° .... if he turns it on low, I'm guessing he will be in the 45° range...It could go a bit lower but I would probably leave it...

The 160lbs on the high seems low, but if he was spraying water on the cond or something, then that reading wouldn't be accurate..






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jjrbus
User

Sep 4, 2017, 5:39 PM

Post #16 of 29 (233 views)
Re: I'm back, AC not freezing up Sign In

Got tied up, AC in house went out and went away for holiday.

The following is with fan on high and set for recirculate.

Anyway drove a couple short runs around town and AC worked, Temp in the 90's AC dash blowing in the upper 40's and no issues. Drove couple hours towards Orlando in the 90's dash temps in 40's and AC worked fine. Great, can tell the forum thanks and offer everyone dinner.

Drive 40 mi to Fort Christmas temp in the upper 80's dash temp in the 40's and condenser freezes up! Drive from Orlando area to Tampa and works ok, not good but did not completely freeze up, blower sounds like it is struggling. Leave Tampa and head home and 30 miles or so into trip and AC condenser is freezing up, can tell by sound of blower struggling? It is in the low 90's, dash temp is around 45 at 65 MPH.

Stopped for gas and I noticed that the seal between the RV part and the truck cab is loose not completely sealed so truck cab AC is going into camper part. Tightened it up and drove the rest of the way home only about 15 miles but AC may have been working right. Can not be sure on short drive, but we had nice cold air.

If the cab was not sealed would this cause the condenser to freeze? Would be the same as driving with window open.

Lower fan speed causes freezing? I replaced bower fan motor last year, would wrong blower be too slow and cause freezing?


Discretesignals
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Sep 4, 2017, 6:06 PM

Post #17 of 29 (229 views)
Re: I'm back, AC not freezing up Sign In

You may have to put the thermister lower in the evaporator coil to prevent it from freezing. The location of the probe is important. If the condenser has ice on it, there is a restriction in the condenser tubes. I'm sure you meant evaporator and not condenser.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


jjrbus
User

Sep 4, 2017, 6:55 PM

Post #18 of 29 (211 views)
Re: I'm back, AC not freezing up Sign In

Yes evaporator, not condenser!


Tom Greenleaf
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Sep 4, 2017, 8:43 PM

Post #19 of 29 (197 views)
Re: I'm back, AC not freezing up Sign In

Quote ">Lower fan speed causes freezing? I replaced bower fan motor last year, would wrong blower be too slow and cause freezing?<"
You also said sounds like blower is struggling? If iced up air can't flow thru so struggles.* New motor if any good spins same speeds as it's told to but the wheel could be bent - out of balance but would be all the time not intermittent - forget that.


* Notes: Slower or lower fan speeds allow more "residence" time for air passing thru so if evaporator is under 32F has time to freeze faster. As said by DS placement of thermistor could fool it. Otherwise if ice it would blow slower, freeze but work then shut it off for 1-2 minutes work again if stopped make a larger puddle. Freezing is noted by seen frost or no dripping when operating.
Please don't say just ''40s" there 10 degrees of the 40s. Any are OK for conditions at the time but seeing 41F could be too low. Takes two thermos - one to know the air temp while driving along coming in thru grille the other in center vent. Note if doing that along with other info the real air leaving evaps rises about 4>5 degrees if you chose just vent above the real air temp with A/C off. Yes it loses that much to area - ducts etc.


Other is make sure the louvers of vents stay open. With time many are just felt to hold where you pointed them or shut one off for a reason. Can redo felt to stay put.


Those should be left pointing UP not down just FYI the cooled air will fall by itself. That also help with recirculating air you don't just send back cooled air instantly should be picking that up off the lower area of the dash.


I don't see a real problem with anything you posted except your concern of blower struggling? Is it really or you just think that?
T



jjrbus
User

Sep 5, 2017, 8:05 AM

Post #20 of 29 (179 views)
Re: I'm back, AC not freezing up Sign In

Thanks for responses.

Fan struggling, Is a definite, not imagination. Big difference in sound fan makes as evaporator is icing up.

vent temperature is not constant so hard to give one number. Took to fill up for gas this morning and after a few minutes of 50 MPH with fan on high and recirculating air vent temp was slightly under 50, ambient is 88°.

Yesterday when evaporator was freezing speed was 65 MPH, ambient was 93° and vent temp was showing 43/45°. Freezing seems to happen after about 30 miles of driving at highway speed.

Thermister was tested as per Factory Service Manual and tested within specs.


Tom Greenleaf
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Sep 5, 2017, 8:27 AM

Post #21 of 29 (175 views)
Re: I'm back, AC not freezing up Sign In

?? How is 43/45° vent temps freezing water to ice? It's possible to see that with enough heat contamination AFTER evap at the exact time pressure would reflect it really happening - do dripping of condensate and if you could watch frost on return line. Yup - if seriously suspect you (or I would) have to read pressure and route hoses to in sight while this happens to confirm that - odd to tape up gauges to wipers or something.


You've had this for some time and did work so it's much more likely not real.
The only reason I see for high speeds with a camper back (right?) is airflow in general is all screwed up IDK maybe creating a vacuum where outside air picks up?
Temp exchange is supposed to create a slight vacuum under the vehicle at speed such that airflow is forced thru grille then down and out under the set up.


Missing air dams? This camper may not be suited to work with this truck? But didn't it work before ever?
Your thoughts and observations are valid the problem is why. Fan motor noise or feel changes may be the new one is already no good or ducts and doors aren't holding for proper flow for another reason then a real struggle sound and feel but it doesn't show freezing anything just yet to me,


T



Discretesignals
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Sep 5, 2017, 8:55 AM

Post #22 of 29 (171 views)
Re: I'm back, AC not freezing up Sign In


Quote
Thermister was tested as per Factory Service Manual and tested within specs


Thermister is probably fine itself, but it is too high up on the evaporator.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


jjrbus
User

Sep 5, 2017, 11:57 AM

Post #23 of 29 (155 views)
Re: I'm back, AC not freezing up Sign In

Thanks for all the input, but this hurricane Irma seems to be heading for Florida, so will have to put this project on hold for I hope only a short time. We are going to pack it up and head north with some friends till the dust settles.

One question does come to mind, Shouldn't the thermister shut the compressor down if it is sensing a freeze condition?


Sidom
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Sep 6, 2017, 2:55 PM

Post #24 of 29 (129 views)
Re: I'm back, AC not freezing up Sign In

The a/c amplifier shuts down a/c operations when it receives a signal of low evap temps...or abnormally high pressures...






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jjrbus
User

Sep 19, 2017, 6:53 PM

Post #25 of 29 (75 views)
Re: I'm back, AC not freezing up Sign In

I escaped Irma's wrath unscathed. I do not have the evaporator out of my RV this is a picture I took when I had it apart, hopefully it will post. The evaporator is upside down, I need to know where I should place the thermister. Any ideas on how to get to it without removing cooling unit?

http://autoforums.carjunky.com/upload/IMG_0016.JPG






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