[Cclaro]

got the compressor to finally cycle as intended. want some opinions on how the ac behaves. 90 degree ambient temps idling the vent temp is around 60-62 degrees (humidity in the 80% area). when I drive the car, with airflow moving through the condenser other than my fans running (high all the time 3600cfm derail fans with shroud covering entire rad) the vent temps will drop to about 55 degrees with your regular street traffic. coolant temps 195-200 with ac on. when the sun goes down the vent temps will be around 55 degrees (ambient temp 80 degrees) but when the car is cruising for long periods of time the vent temps will drop to the 50 degree range. I saw as low as 48 while going around 45 mph for a couple minutes straight. It sounds like there's an airflow issue across the condenser so I was thinking of putting in a pusher fan in front of it to assist with cooling in stop and go traffic. compressor and liquid line are brand new. does this seem normal? am I asking for too much given I live in south Florida? putting water on the condenser cools the vent temp as well given that the water is removing large amounts of heat from it. like I said this sounds like an airflow issue to me. what do you guys think.

 

[Cclaro]

Most likely an airflow issue like you said. Though I would verify head pressures while you’re at it. I wouldn’t be surprised if it was a little low.

For reference, my 87 Grand Marquis with the stock mechanical fan and r134a will blow around 50-55 in the middle of the day at idle. It’ll get down into the low 40s while driving. And this is in southwest Florida in the summer.

it'll be around 57 just driving 15 mph around my neighborhood so I think in a couple weeks im going to install either a single large or two small pusher fans spliced from my primary fan wiring to just come on whenever the derails come on.

 

[Cclaro]

Do you by chance have a fan shroud? I think a pusher fan will help but I think you should find the root cause.

yeah I have a fan shroud as well as a 3 core aluminum radiator which I think impedes airflow through the condenser. car cools off fine with the ac off and will get to around 200 with it on. for the pusher fan I was thinking of a single 16" spal that pulls and advertised 3000 cfm. I think that across the condenser would improve the temp at idle considerably

 

[Cclaro]

I would put gauges on it like stated and check pressures. You want to use a manifold set that displays high side and low side pressure.

Give us the high/low pressure as well as the static (system off) pressure and the ambient conditions (temp/humidity).

Static pressures resting at 70, with the compressor jumped it would stay at around 20-25 on the low side (can’t remember the high side but it was around 220). With the compressor cycling and coolant temps at around 175 it would drop it all the way to 20, kick off the compressor, rise to about 45-50 then kick back on. High side pressure would go to about 230 and back down as the compressor cycled. Took just shy of 3 cans of refrigerant (35 oz). At night temps at the vent are nice and cool at around 52-53 as the cabin cools down but during the day it really struggles at idle. It improves with air flowing through the condenser

 

[Cclaro]

A pusher fan is going to restrict airflow while driving. A 3 core radiator is not helping either. 3 cores will have more restriction than a 2 core of the same thickness simple because of the fin breaks between cores. You get turbulence and air slows more each gap between fins A 2 core with 1 inch tubes would be better than a 3 core and give you more than enough cooling.

Have you put gauges on it? Gauges will tell you if your pressures are good. Low refrigerant will cause the vent temps to be higher than normal too.

I was thinking of a 14” pusher fan because the car cools off very well at speeds. Never had an issues cruising on the highway. I was gonna add the air damn underneath the car as well but for low speed cruising I don’t see why a pusher fan would hurt it. It would purely be to cool off the condenser. The car will maintain 180-185° Coolant temps with the ac off during the car when it’s 100+ degrees outside and with the ac on it’ll run around 20° hotter

 

[Cclaro]

205 is the normal temp it should be running at with ac on. That's the normal operating temp for a SBF. When cruising down the highway your car gets most of it's cooling from the bottom of the radiator/condenser which is the part getting fresh air. With a shrouded fan over the condenser it is going to block that area off. You would be better off investing in a quality 2 core radiator and seeing if there is possibly a less restrictive condenser available for your car. When cruising above 35mph your getting a lot more air into the radiator than a fan can push. It becomes a restriction. In my car, i'm upgrading to a 97 condenser because my giant fmic + standard condenser blocks too much flow at low speeds causing my car to hit 225 on hot days. If i remove the condenser, it runs at normal temps.

It won’t be a shrouded pusher fan otherwise I’d agree with being too much of a restriction. I’m considering biting The bullet and replacing the evaporator core as well. I compared the ac to my buddies 95 and his vents seem to blow much harder than mine in every setting. I replaced the blower motor and resistor so I think the evaporator could be clogged up with crap which isn’t helping my situation. The ac never worked fantastic when I bought the car with an HCI 302. I really wanna get it dialed in because it’s brutal in the summer.

 

[Cclaro]

I hear you. I live in Colorado which normally is 100+days often although this year it's been cooler and rainy this whole summer. It rains almost every day for the last few months which is how it was in the 90s with i moved here. The biggest upgrade you could do is to put a 97-98 condenser in it. It will help allow your radiator to pull more fresh air through it. My ac blows really cold when it was installed but the problems i listed above have forced me to upgrade to condenser. For now i am running without a condenser. I verified with LMR 2 days ago, their condenser for 96-98 is the less dense 97+style. They sent me pictures of the fins so u know for sure it's the better sn95 version. It's worth doing if you're serious about having ac.

Is there any modification to be done or is it just a straight forward replacement?

 

[Cclaro]

According to @fasterthangas it's a direct swap. Pictures look the same. Fasterthangas did he did it on a couple sbf sn95s. I'm ordering mine here in the next coupe days.

I’ll give it a look but I’m leaning towards adding that auxiliary fan just because in low speed situations I feel like it’ll help keep consistent airflow through the condenser. I think I’m gonna end up replacing the evaporator core in the car to eliminate that component as a possible source of leaks plus as mentioned earlier i noticed the lacking vent performance which makes me think it’s clogged up with crap

 

[Cclaro]

Before you replace it, check your pressure levels. Fyi, you have to cut the ducting on sn cars to get the evaporator out. It's not removable like the fox. I did mine 2 years ago because mine was full of metal shavings because someone cut the metal hose instead of removing it at the coupler.

I’m gonna check the pressures before I replace it when it’s static to see if I lost anything. If there’s no change then I knkw the system isn’t leaking and there’s most likely just an airflow problem. If it is leaking then the only place I can think of is the evaporator because I’ve already hit the system with some dye and a UV light and everything is clean under the hood. Might have a shop use one of those Freon wands to see if anything is coming out of the evaporator if it is leaking. Probably gonna replace it just to see if the vents blow any harder.

 

[Cclaro]

some loss over time occurs if im not mistaken. it permeates through the hose very slowly from what i remember. im not 100% sure on that though so Im sure someone will correct me if I am wrong.

I’ve read about it too, I just see people boasting vent temps in the mid 40s to 50s and my car struggles to reach those temperatures at any given day which is frustrating hence why I feel like it’s an airflow issue or clogged evaporator.

 

[Cclaro]

low refrigerant will cause that and if your on an AC charge from 7-10 years ago, my bet is its low. Gauges will tell you everything you need to know.

We just filled it up with 35 oz of Freon, I’ll be looking at how it performs tomorrow when the ambient temp is high with direct sunlight. I’d be happy with 60° Vent temps and ambient temps at around 100°

 

[Cclaro]

what was the ambient temperature when you got those pressure reading

Unless it was 60-65°, the low pressure seems to be low.
the high pressure reading would indicate an ambient of about 85°+

did you replace the orfice tube?

Brand new orifice tube and the ambient temperature was 81°

 

[Cclaro]

I agree. knowing the ambient conditions are critical because the pressures will vary. If the outside temp was higher, i would suspect not enough refrigerant based on those pressures. You really want to report pressures under max stress conditions. 1500+RPM, fan speed on high, doors open and report the pressures while still at 1500+ RPM

Cclaro, did you fill by weigh by using a scale, or just by estimating based on can volume?



Does spraying the condenser with water improve performance? That would signify an airflow issue, but your high side pressure doesn't seem high enough to support this.

I agree that your vent temps should be better. My 8-year old Taurus puts out vent temps in the low 40's at idle and will drop to 40 degrees once moving. My fox will do vent temps in the 35-38 degree range while just iding, but that's with a brand new fresh R-12 system.

Spraying with water does improve the vent temperatures. The cooler the ambient temperature the cooler the vent temps usually because the cabin temperature drops as well. We filled it by weight using a scale. I can check the low side once more to see the pressure now since it’s around 95° out

 

[Cclaro]

So I did a couple things, low side pressure while running in 94° ambient temps is around 33 psi, I couldn’t check the high side my buddy has the proper gauge set so I could only look at the low side. I let the car run till operating temp on normal ac with the windows open and from 94° ambient temps (probably closer to 100 due to humidity) it was spitting out vent temps of about 67°. As I put it on Max ac the temps drop to around 63°. Cabin temps were just shy of 98 degrees. It wouldn’t get any cooler until I closed the windows and began to drive it around (just 15-20mph) and immediately the temps began to drop with just some airflow going through the front of the car. Driving around stop and go at those speeds I was able to see vent temps at around 57°. I’m sure higher speeds with longer periods of driving would’ve yielded some lower temperatures as well. I came back into the drive way with the car sitting at around 195° coolant temps and it was able to hold around a 62° Vent temp. I sprayed the condenser with a little bit of water and watched the temps drop to around 57.5. Windows up ac going with cabin temps at around 85° at this point. When I sit there at 1500 rpm for a couple of minutes the temperature will actually go up a bit as the compressor cycles due to me spraying it with water and dropping the pressures due to the temperature change considerably. When it heats back up the compressor will stop cycling and the vent temps will begin to drop from around 63° to 58°. It’s a 93° day with temps that feel like 103 and 55% humidity at the moment. It still sounds like an airflow issue and as mentioned before with the air not really blowing as hard as I feel it should possibly a dirty evaporator as well. I’d like to know what you guys think about the evaporator theory as well as the results discussed in this Post. Sorry about not being able to grab a high side reading, in a couple days I’m gonna get the gauges on again to check when it’s hot out to verify all pressures

 

[Cclaro]

If it's 93 outside your low side should be between 45 and 55 psi, high side around 270ish . That tells me your refrigerant levels levels are low.

so would I forgo the addition of freon by weight and rely entirely on pressure alone? I saw someone mention that above but wasn't sure

 

[Cclaro]

You need to verify both high and low side to make sure both are reading low. If both are reading low you would add more refrigerant. I know you said your replaced the orifice tube. Anything else replaced and was your leaking before your replaced parts? Did you add oil to the system?

new compressor, accumulator is less than a year old, condenser less than a year old. only items I haven't replaced are the lines (minus the liquid line containing the orifice tube) and the evaporator. we couldn't find any leaks with the dye in the bay so if there is a leak its gotta be the evaporator. I can verify pressures in a couple days I have some extra R134 I can add to the system

 

[Cclaro]

How much oil did you add? The new compressor usually comes with some oil but not enough for the whole system. Sometimes they have no oil. Do you know if yours had oil?

It came with oil I didn’t need to add any

 

[Cclaro]

At this point, you really can't. If you had the machine, you would recover the refrigerant, pull a vac and recharge again. Since you don't really have that, you need to switch to using pressures.

I don't think you need to add much more, but do agree with Dwain that you need a little bit more. However it's possible that's because you didn't have the proper level of oil in the system.

WOuld need to see high side pressures here to really tell you next steps. Remember, you want to take your readings over 1500 RPM with fan to max and the doors open (to avoid any recirculating air). The goal is to cool purely 90 degree (or whatever outside temp is) across the evap and no recirculated air.

I don't have an SN95 service manual in front of me but I beleive low pressure cutoff is around 20psi. When you hook up the manifold guages with high/low pressure guages, pay attention to the low side when it drops and note where the pressure cuts off. When it cuts out, note the high side pressure. If it's very high 300+PSI or more, that would suggest either a blocked orifice, or poor airflow across the condensor. If you spray water and it drops, you need more airflow.

If the low side cuts off at 20psi or so and your high side is sub 200psi on a hot day, you just need more refrigerant. In fact, on a hot humid day, that compressor shouldn't really cycle much at all. Should hold pretty well around 40-45psi and your high side should be 250-275ish.

You should be able to maintain 40-45 degrees vent temp at idle with doors open.

But I also do think you have an airflow issue through that condenser.


Good luck, as i will be away from internet for a few days

Very helpful post thank you

 

[Cclaro]

At this point, you really can't. If you had the machine, you would recover the refrigerant, pull a vac and recharge again. Since you don't really have that, you need to switch to using pressures.

I don't think you need to add much more, but do agree with Dwain that you need a little bit more. However it's possible that's because you didn't have the proper level of oil in the system.

WOuld need to see high side pressures here to really tell you next steps. Remember, you want to take your readings over 1500 RPM with fan to max and the doors open (to avoid any recirculating air). The goal is to cool purely 90 degree (or whatever outside temp is) across the evap and no recirculated air.

I don't have an SN95 service manual in front of me but I beleive low pressure cutoff is around 20psi. When you hook up the manifold guages with high/low pressure guages, pay attention to the low side when it drops and note where the pressure cuts off. When it cuts out, note the high side pressure. If it's very high 300+PSI or more, that would suggest either a blocked orifice, or poor airflow across the condensor. If you spray water and it drops, you need more airflow.

If the low side cuts off at 20psi or so and your high side is sub 200psi on a hot day, you just need more refrigerant. In fact, on a hot humid day, that compressor shouldn't really cycle much at all. Should hold pretty well around 40-45psi and your high side should be 250-275ish.

You should be able to maintain 40-45 degrees vent temp at idle with doors open.

But I also do think you have an airflow issue through that condenser.


Good luck, as i will be away from internet for a few days

When it was 82° outside the high side pressure was about 230 psi as the compressor was kicking on and off. This was with the windows up at night so not exactly what you’d like to see in terms of the test. Will hook up some gauges to see

 

[Cclaro]

Compressors never have enough oil for the whole system. Mine came with 3 ounces. The system needs 7.

I believe mine came with 5