Forgot more than I know

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bevis
Posts: 19
Joined: Thu Jul 30, 2020 12:00 pm

Re: Forgot more than I know

Postby bevis » Mon Aug 03, 2020 8:18 am

I have some more input.
Had the car parked in the big garage because of fake hurricane. we had no winds and zero rain. we are only 10 miles from the open Atlantic Ocean.
So I screwed up my lower back getting ready for storm that never came. This morning I hobbled out to the big garage to get the car out so I could get to the chiropractor. I started it up and backed it out and let it sit and idle while I got that big ass 10x12 door shut .
When I got back in the car, it was blowing 47 degree air. the ambient was 76.5 and humidity 95%. so the ambient was way down from my testing the other day. I drove the car down the driveway to the house garage and now its blowing 45 degree air. I leave and drive to the Chiro and during the drive on a road about 3 miles without stopping and 2000rpm, its blowing 45-48 degree air. I come to a red light and the temp goes up to the 50's low 60's. leave that red light and it cools down more. during the 3 mile road with no stops, the car is at operating temp and its blowing 40's air temps. I'm thinking that takes the reheat issue out of the equation. So it appears that the drop in ambient has a massive impact on the operation of the ac. Am I on point thinking that its either restricted or overcharged ?
Also, can I strap a digital temp gauge to the input of the evaporator on the low pressure side of the orifice tube and adjust the charge from that temp ? If so, im unclear how to get the correlation of temp to pressure.
tbirdtbird
Posts: 34
Joined: Sat May 02, 2020 1:48 pm

Re: Forgot more than I know

Postby tbirdtbird » Mon Aug 03, 2020 11:18 am

From initial post,
"24" fan on high blowing directly into the grill of the car"

May have condenser issue nonetheless.
When temps get hotter instead of the fan use a garden hose on the condenser to see what happens
bevis
Posts: 19
Joined: Thu Jul 30, 2020 12:00 pm

Re: Forgot more than I know

Postby bevis » Mon Aug 03, 2020 12:29 pm

new condenser last year but you never know
Al9
Posts: 203
Joined: Tue Mar 10, 2020 3:26 am
Location: Southern Europe

Re: Forgot more than I know

Postby Al9 » Mon Aug 03, 2020 12:48 pm

Or way too much oil inside...
bevis
Posts: 19
Joined: Thu Jul 30, 2020 12:00 pm

Re: Forgot more than I know

Postby bevis » Mon Aug 03, 2020 12:57 pm

when I did the compressor / accumulator / condenser changeout last year
I dropped exactly 7oz of PAG 46 into the compressor
Dougflas
Posts: 341
Joined: Mon Apr 18, 2016 6:10 pm

Re: Forgot more than I know

Postby Dougflas » Mon Aug 03, 2020 3:04 pm

airflow across condenser
bevis
Posts: 19
Joined: Thu Jul 30, 2020 12:00 pm

Re: Forgot more than I know

Postby bevis » Mon Aug 03, 2020 4:14 pm

both fans kick in and run full tilt and then cycle off and on. when im using the 24" fan, they dont kick on until I run the rpm up for extended periods of time. the better or worse operation of the ac / vent temps are chasing around with the ambient. I may have it over charged . can I take a temp reading at the inlet of the evaporator and adjust the charge with that temp ?
tbirdtbird
Posts: 34
Joined: Sat May 02, 2020 1:48 pm

Re: Forgot more than I know

Postby tbirdtbird » Mon Aug 03, 2020 4:42 pm

The method you want to use to adjust the charge is unconventional, and I am not convinced the charge level is wrong.
Doug just followed me along with the idea of not enough airflow, and he knows lots more than I do.

We do a lot of custom work here, and we always make sure the condenser fan is on if the compressor is on, period. We will use a relay off the main on-off dash switch to run the condenser fan. No cycling for us.
We have also re-wired OEM systems to make sure the condenser fan is on at all times the compressor is on. The condenser function is absolutely critical to the system.

We have also replaced condenser fans that seemed to work OK but in reality they get tired and old and don't blow enough air anymore. Under these circumstances, the engine itself will typically not overheat but the AC function will be sub-optimal.

All of this is why I suggested misting the condenser with a hose, with the engine at 1800 rpm to see if the vent temp comes down.

You are accustomed to a residential condensing unit where the compressor and the fan both come on together and you never even give it a thought. Those 220V fans don't seem to get tired they just go out or the cap dies. You have changed out lots of condensing unit fans in your career, for sure.
bevis
Posts: 19
Joined: Thu Jul 30, 2020 12:00 pm

Re: Forgot more than I know

Postby bevis » Mon Aug 03, 2020 6:07 pm

that's pretty damn spot on !
I was trying to correlate why you wanted the condenser misted .
Now I know.
As far as the fans, I could use a 30 amp relay and tie the coil voltage for that relay
to the hot compressor wire and feed the fans from straight B+ voltage across that relay
tbirdtbird
Posts: 34
Joined: Sat May 02, 2020 1:48 pm

Re: Forgot more than I know

Postby tbirdtbird » Mon Aug 03, 2020 9:41 pm

Wonder what is controlling the fans now?

Imagine cycling the fan on a residential CU (Condensing unit)?

What is the gap between the condenser and the radiator?
Any trash, leaves, etc between the two?
Is there any way air can get around the condenser before it goes thru the radiator? You may need air dams around the perimeter
Are the fans tired?

Misting costs zero and can help a lot with diagnosis

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