Struggling A/C at idle/ low speed/ high ambient temps. (1 Viewer)

Joined
Jan 23, 2018
Messages
148
Location
San Diego, CA
Looking for some advice on where to start.

The Truck:
-1HDT 1991
-PDI Front Mount intercooler (this appears to have had an even more negative impact)
-A presumed original AC system that does work.

Symptoms:
-Struggles to stay cool at idle
-Really struggles if ambient is above 90F ambient
-Struggles at low speeds under 35MPH

The system doesn't have a leak that I can tell. It is full I have confirmed with a bottle of refrigerant from auto store. It was actually past the green and into the yellow? (not sure if this is a negative effect but the can just says it is full and to stop adding). The condesner appears to be original and quite old obviously, I suspect this may be part of the issue. Sometimes it is so cold I have to have it on low and have the temp range adjusted in middle on the console and this is usually on the freeway doing 60mph. Sometimes even with the compressor running and on high its mediocre at best.

Before I buy a new condenser I wanted to see what some of you have to say.

Cheers!
 
Joined
Jan 23, 2018
Messages
148
Location
San Diego, CA
You know the idle up solenoid is working, is it at factory set point?
I really don't think this is the problem. if it was the AC would start working when I'm moving which depending on outside temps it doesnt.

However I dont know the AC idle RPM from the FSM but i will check and its easy to adjust.
 
Joined
Jul 29, 2005
Messages
317
Location
north bay, ontario
 
 
 
I would have have the pressure checked to be sure it's actually full. I wouldn't rely on a throw away can, just saying. Is the condenser fins cleaned of debris and whatever is in front of it like a intercooler?
 
Joined
Jan 23, 2018
Messages
148
Location
San Diego, CA
I would have have the pressure checked to be sure it's actually full. I wouldn't rely on a throw away can, just saying. Is the condenser fins cleaned of debris and whatever is in front of it like a intercooler?
Yea the condenser is old and has bends but it’s clear of junk, same as the intercooler but the intercooler is brand new
 

ceylonfj40nut

Waiting for Barn Time
SILVER Star
Joined
Jan 11, 2015
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3,072
Location
TX
 
Hook up real gauges and tell us what the readings are at idle with and without compressor on with AC on high with windows closed. Rev/ hold at 1200 rpm and share pressure readings. What altitude are you at? Also share ambient temp during above tests. Is this r12 or r-134 refrigerant?
 
Joined
Jan 23, 2018
Messages
148
Location
San Diego, CA
Hook up real gauges and tell us what the readings are at idle with and without compressor on with AC on high with windows closed. Rev/ hold at 1200 rpm and share pressure readings. What altitude are you at? Also share ambient temp during above tests. Is this r12 or r-134 refrigerant?
I don’t have the gauges capable I’ll need to buy some. It is r-134 for sure though. I’m at sea level currently but I noticed a major negative change when I hit 3,000ft during this road trip I’m currently on. It seems I may just need to bite the bullet and get it checked out at a AC shop.
 
Joined
Jul 29, 2005
Messages
317
Location
north bay, ontario
 
 
 
After reading my 60/70 fsm and there can be many reasons it's acting the way it is. Replacing parts is not a way to troubleshoot but having a expert check it over would be wiser, just saying. It can be something simple or ouch, welcome to the world of mobile AC and you're not alone. Let us know on the outcome.
 
Joined
Jan 23, 2018
Messages
148
Location
San Diego, CA
So I finally got around to testing it today. These are my pressure readings at idol
Which was 42psi low side 315psi high side
3BF540AC-2FA2-4430-B44C-B35E2876033B.jpeg

And then at 1200 rpm
8F9636A5-F29D-46BD-BF31-DE0A45AC4F07.jpeg

I still haven’t been able to track down a specific graph for ambient temps and high and low side values per a FSM. I used something generic and off the internet. And according to that my low side is ok but my high side is too high. Today it was 85 and above 60% humidity
B87C1029-5ECE-4AF1-BBB3-30B055B85EDA.png


Knowing this I’m suspecting I have a blockage somewhere and I’m thinking it is my AC drier because it’s foaming white in the sight glass with the AC on.

thoughts?
 
Joined
Jul 29, 2005
Messages
317
Location
north bay, ontario
 
 
 
My 85bj60 was using R12 and high pressure was around 206-213psi and low pressure was 21-28psi.
IIRC, the R134A runs at a higher pressure, I've no clue how much more.
Could there be moisture in the system?
 
Joined
Jan 23, 2018
Messages
148
Location
San Diego, CA
My 85bj60 was using R12 and high pressure was around 206-213psi and low pressure was 21-28psi.
IIRC, the R134A runs at a higher pressure, I've no clue how much more.
Could there be moisture in the system?
I wouldn’t imagine after running a vacuum on it for an hour
 
Joined
Jul 18, 2018
Messages
45
Location
Southern California
Do you have a condenser fan? Many of the Hdj81s did not come with one and if you have a front mount intercooler there may not be room for it as well. They are known to have trouble cooling at higher temperatures and low speeds when not equipped with the condenser fan. Should do fine on the freeway though.

Also check that your evaporator is not clogged up. There is a metal sensor screw to the side of it that you can takeoff and peek in there. Mine wasn’t too bad, but I’ve seen YouTube videos online where they are completely Clogged up with debris.

I retrofitted mine with the fan from a Toyota Sequoia. There are several threads on fitting aftermarket ones as well, but I do not have an intercooler.

Not Sure about the pressures for R134a, Mine runs R12 still and the FSM specifies appropriate pressures at 2000 rpm.
 
Joined
Dec 7, 2019
Messages
398
Location
North Carolina, USA
If your condenser is not properly cooled then your AC will not put out cold air. My retrofit AC has the condenser too close to the radiator so once the engine gets hot it radiates heat into the condenser and the AC doesn't cool effectively. If you have some type of non factory add on intercooler in front of your condenser which is heating up the condenser then that is likely your problem.............In my application my AC is not cold at idle cause it's pumping slow, it is great around town at slow speeds. After 10 min on the highway the cold air stops as the radiator heat soaks the condenser.
 

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