Automotive Air Conditioning Information Forum

I have two Mazda B2200 pickup trucks.

Both have had the AC redone by me, entirely. Took it all apart, flushed each component and went new with driers and expansion valves. All new green O rings throughout.

Truck 1 I did 2 years ago. Its been great. Here in the hot hell of Mississippi I could get the vent temps to 40F and sometimes 36F in the dead heat of summer.

It was my first time messing with and installing AC from scratch. I did well.

I got me truck 2 and decided to get the air in it working correctly.
Long story short. Snowballs at the vent. Same good story as truck 1.

Both are R134A, twenty percent less of the R12 charge, very used compressors, but pressures are good. Trucks run good temps at the coolant gauge. Life is great.



HOWEVER

I decided that truck 1 the compressor was making louder more pronounced noise than it had been. Mind you its always made some noise, but sounded like it was going to make its exit later down the road, maybe months.

I ordered a BRAND NEW one from ackits. Its really new and fresh. Very stiff to rotate by hand, which is fine, its new. I am not used to it, I am used to these older used compressors.

Anyways. I replaced truck 1 compressor with new and I can’t get it as cold as before.
Not sure why just yet.

I pulled a good vac on it, charged it with the same amount as the other truck. I have it down really well. It likes about 20 oz compared to the 26.5 r12 charge it calls for.
It cools but I have noticed that the trucks thermostat is now higher than it used to be and the fan clutch kicks in some.
The condenser is hot is best I can figure but not sure why.

Could it be that the compressor is doing it, like its compressing the gas way better than the used pumps, and its causing more heat?

I have fiddled with the levels of charge and I can’t seem to find a happy place and have lost my way along the way. I do not currently know how much is in there right now. I am going on pressure readings alone right now.

Need advice.

For all I know, it may just need a small condensor fan to help, or it may be under or over charged just a smudge one way or the other, OR what if its compressing so well that it will work of one 12 oz can? I really am unsure at this point. Also Its only 5 degrees difference in vent temp compared to truck 2, but it takes longer to get there and Its just not what it was before the compressor change.

Ideas?

Reference Numbers Recorded at different days.

TRUCK 1 (new compressor)
with Box Fan in front (shady carport)
Ambient temp 85F Humidity 50%
Windows down Fan on high
AC ON
RPM 1500
Low is 33
Hi is 300-325

TRUCK 2 (used compressor)
with Box Fan in front (shady carport)
Ambient temp 92F Humidity 50%
Windows down Fan on high
AC ON
RPM 1500
Low is 33
Hi is 250-275

digeratimvp wrote:I have two Mazda B2200 pickup trucks.

TRUCK 1 (new compressor)
with Box Fan in front (shady carport)
Ambient temp 85F Humidity 50%
Windows down Fan on high
AC ON
RPM 1500
Low is 33
Hi is 300-325

I actually own a 1988 Mazda B2200 truck, mine since 1994, 216K miles now. But mine is still R-12. I also bought and am using a new compressor from ACkits.com in it, I'd say about 5 years now.

Looking over your situation, what jumps out to me is the high side pressures on TRUCK 1. Of course you evacuated the system before you added your R134a. so air in the system gets ruled out. So I'm thinking that your high side pressure being high could be due to a faulty fan clutch - I've had to change mine out every 6 years or so here in Arizona.

Another test would be to mist the front of the condenser with water while running, and see if the high side pressure drops. Your TRUCK 2 high side pressures are more in line with what I would expect.

Did you remove the R-12 type mineral oil when it was converted to R134a so R134a oil could be used? Did you add or measure oil in the new compressor?

Yes I completely flush everything of old mineral oil 2 years ago and went with Pag 100, and all was fine.
This new compressor, came with pag oil, but I dumped it and put in the same amount that came from the old compressor. All new oil, it was like 3 oz.

The fan clutch was suspect, but its working properly and its new. When the truck does indeed get too warm, it activates and cools things down. You can see the High temp drop when the fan blows hard.

Also yes the high temps dropped when I added misting water one day during my testing.

Did you backflush the condenser with solvent to flush out any particles? And use a new drier?

I flush everything on the install in 2016. This summer I just wanted to replace the compressor, so I replaced the compressor and drier. I didnt feel the need to flush the condenser at this time.

I can't see why a new compressor could be a source of higher temperatures or too-high pressures.

At this point I think I'd recover refrigerant, pull good vacuum, and add refrigerant by weight, to make sure that you're not overcharged. What year are your B2200s? It seems that these can have differing refrigerant capacities, depending on the year, less is used on 1991-1993. My own 1988 B2200 sticker states 30 or 32 oz for it (R-12).

I asked about the flushing of condenser because you said the previous compressor was noisy; I understand, possibly you replaced that before there was particle build-up, like the situation I had 2 years ago with our 2005 Yukon: compressor was cooling well, but sometimes would "chug" and break its compressor belt. So on it I replaced just the compressor, did not even change out accumulator or the condenser on it (a parallel flow condenser that cannot be correctly flushed).

I have a 1988 (truck 1) and a 1990 (truck 2)

The 1988 did not come with AC at all. I sourced all the used parts from a parts truck in 2016 and installed it all.
Everything was completely flushed out, and the compressor was good. I flushed it with pag oil, put a new bearing on it and all worked great.
The "noise" was there from the start. It was just a mechanical noise never had issues with it. Over the years the noise seemed louder to me. This may have been because I was comparing it to the the 1990 truck that I just got the air working in. When I replaced the compressor, the only thing was the front seal has started to leak some. When I drained it, the oil was fine, no signs of metal anywhere. I was going to repair that seal and put it on the shelf as a backup.

The 1990 truck CAME with ac but I took it all out and flushed it all just like I did on the other truck. I put a used compressor on it, and its been fine. I have evacuated and charged several times. I believe around 20 oz on the 1990 is a nice sweet spot. Under the hood of the 1990 it says to use 1 lb 10 oz of r12 so thats 26.5 oz right? So math tells me 26.5 * .80 = 21.2 but I feel like it cools best with a little less.

All the AC parts on the 1988 came from a 91 model truck. Under its hood was the same 26.5.

However in my notes when I first did the 1988, I seems that I wrote down that I used 2.5 cans. That would be over charging but it sure did cool well if that was correct. I am not wanting to try that now as the pressures on the high side get crazy high.

Maybe I should just evacuate, and pull a good 4 hour vac then charge back with 20 oz.

I hate for it to not be the same as the other truck and the weather is cooling off some, making this difficult to get right.

---------------------

Today /this morning, when I came to work, I came in the 1990, drove it home at lunch, recorded temps, its 88-90 F outside, and from work to home, which is 5 mins, or 11 mins, it had a vent temp of 40-43 F

Then I drove the 1988 (new compressor) back to work, and traffic lights messed me up, but it was about the same vent temps. Went up some when I got back to town during lunch rush and had to stop some.

I could tell the temp gauge on the truck was rising due to condenser temps. It would be right on par with the 1990 if it would have cooler condenser temps.
On the 1988, there is a new radiator, new thermostat, new fan clutch, new water pump, its fine on all that.

I checked the condenser for obstructions and found none. I may take the grille off, spray the condenser with something and hose it off really good just to be certain.

I am wondering if I should evacuate, take it out, blow it out, then add a little oil back to it, put it all back together, vac it, and charge and see?

digeratimvp wrote:However in my notes when I first did the 1988, I seems that I wrote down that I used 2.5 cans. That would be over charging but it sure did cool well if that was correct. I am not wanting to try that now as the pressures on the high side get crazy high.

2.5 cans is too much !!!

digeratimvp wrote:Maybe I should just evacuate, and pull a good 4 hour vac then charge back with 20 oz.

I like that plan. 1 hour vacuum should be fine. Then do a 1/2 hour leak down check.

digeratimvp wrote:I am wondering if I should evacuate, take it out, blow it out, then add a little oil back to it, put it all back together, vac it, and charge and see?

I don't see where blowing the oil out of the condenser and then adding back some would be helpful, unless you added considerably too much.

Yeah I was talking about blow out the condenser just to see if it had a blockage of any kind. Doubtful.

Yeah the 2.5 cans if my notes was correct, was working, but who knows if that was correct. I have learned so much since then.

Today this afternoon, it was just not cooling all that well and it was about 90 outside so I decided to connect the manifold gauges and see where it was. It was at about 28/230 so I decided to add 3 oz of 134a and its cooling a lot better. It was only 84F a little while ago, its in the afternoon and it was I saw it get down to 35F at the vents, so Im gonna leave it be for now.

digeratimvp wrote:Yeah I was talking about blow out the condenser just to see if it had a blockage of any kind. Doubtful.

Yeah the 2.5 cans if my notes was correct, was working, but who knows if that was correct. I have learned so much since then.

Today this afternoon, it was just not cooling all that well and it was about 90 outside so I decided to connect the manifold gauges and see where it was. It was at about 28/230 so I decided to add 3 oz of 134a and its cooling a lot better. It was only 84F a little while ago, its in the afternoon and it was I saw it get down to 35F at the vents, so Im gonna leave it be for now.

If the cooling drops off, then you likely have a leak somewhere.