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Filling gap between radiator and condenser

ChevyMan on Sat June 20, 2009 5:50 PM User is offline

Year: 1985
Make: GMC
Model: Suburban
Engine Size: 350
Refrigerant Type: R134a
Ambient Temp: 95
Pressure Low: 40
Pressure High: 295

It's hot today. I'm working on my truck again. After doing a lot of researching on the net, I decided to go with an electric fan setup from a Ford Windstar van. It has two single speed fans. I wired them the same way Ford did, that is they are connected together to one relay. They are single speed. I have them wired to come on continuously with the AC. They pull a huge amount of air. Much more than the clutch fan did at idle. I think they will work well.

OK, enough with the background info. Here's my problem. The condenser is fitted into the code support, but there is a 1" gap on three sides of the radiator and the core support. I am at a loss as to what to use to fill this gap. I really think something flexible like pipe insulation might work, but I'd like to hear from someone who has been here before.

By the way, my vent temp is 48 degrees after a 10 mile drive. It is 95 degrees outside. Still pretty warm inside the truck. There is no headliner. This morning when it was more like 75 degrees outside at 6:30am The vent was 38 to 40 degrees. Does that seem OK?

TRB on Sat June 20, 2009 9:15 PM User is offlineView users profile

Any hard foam or insulation material should do the trick.


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fonebone on Sun June 21, 2009 10:51 PM User is offline

Hi ChevyMan; No headliner insulation just cooks you in that cab. Do everything to cool down the inside. Put some insulation up there, darken (as much as local/state laws allow) your side and rear windows with blackout. In bright sunlight that sun has a lot of power to heat that cab. Just for a trial, try driving in a shady wooded area and watch it cool the cab down to a more comfortable temp. I still feel you might be just a tad undercharged. You should be a few degrees lower on vent temps, and at those hot outside temps a couple of extra lower degrees makes all the difference inside. But--insulate that cab roof, blackout those windows! By the way, how fast were you going during those 10 miles? Around town, highway? I'd still recommend (your other post) a new fan clutch along with those electric fans to pull the max CFM across that condenser. Every bit helps to lower vent temps!

Edited: Sun June 21, 2009 at 10:57 PM by fonebone

ChevyMan on Mon June 22, 2009 1:13 AM User is offline

Thanks for the tips. I had some 1/2" blue-board (styrofoam) glued up there, but it fell down due to me using the wrong kind of glue. Gotta get that back up. It makes a big difference. The truck is a dark color also. The long side windows and the back side door windows came tinted very dark from the factory. I tinted the front side windows and the rear barn door windows a shade lighter. It would not hurt if they were a little darker.

As for the fans, I am using the electric fans alone. They are in their normal position behind the radiator. I found some heavy duty rubber weatherstripping that I filled the gap with. That was a big help. It is funny you should say that I'm a little undercharged. This morning the AC wasn't working well at all. I found that the o-rings where the shell meets the body of the compressor were leaking badly. I would have just replaced the o-rings but the compressor is at least ten years old, so I just replaced the whole thing. I drained about two ounces of oil from the old compressor, so figuring I lost some due to the leak, I added four ounces of oil to the new compressor. It is too soon to tell how it is working. I am hoping for the best, but I know that system is too small for the truck.

Oh, and about the speed on that trip. It was half city and the half highway. Top speed was about 55. I will get some more pressure readings and see how it looks now. The old R-12 sticker says 3.25 lbs. That is 53 ounces. I charged it with 4 can, or 8 ounces minus the loss while changing cans and whatever I lost in the hoses. I'd say it has about 45 or 46 ounces in it. Maybe I should add a little more. I'll just have to wait and see.

fonebone on Mon June 22, 2009 7:26 AM User is offline

Hi ChevyMan; Am I correct that you removed the stock steel fan/clutch assy., and shroud (how else could you fit those electric fans behind the radiator, as stated, not in front of it?) to draw air in across the condenser/radiator??? If so, you will read here many times you cannot better the factory setup. Those engineers know their stuff. I would still like to see you put in the new fan clutch with sealed shroud, then send your results. You will never equal the factory setup with electrics pulling air in. Those pressures will remain high, with corresponding higher vent temps/ hot driver- A killer setup would be fans blowing in front of the condenser AND a new fan clutch with sealed shroud. Also, are you using the old R-12 condenser? If so, junk it !! Put the largest parallel flow (available at this site) you can fit in front, have the good folks here make you short "jumper hoses" to connect to the high/low side hoses that you have, and watch those vent temps AND high side/low side pressures drop. That's what I run on my car, a '79, and what a difference! I overlooked that completely. Your setup is fine, otherwise.

Edited: Tue June 23, 2009 at 12:59 AM by fonebone

ChevyMan on Mon June 22, 2009 9:40 AM User is offline

I was trying to avoid $200 for a fan clutch. Also hoping for the claimed fuel economy increase from removing the clutch fan. I did not harm anything and still have all the parts, so it could be put back in 15 minutes. I am not sure if I could squeeze those fans in front of the condenser. If I did, I'd have to run them backwards (electrically). I hear that will reduce their efficiency. But If I have to put the clutch fan back, I might do it. I am still trying to see how it is going to work after I replaced the compressor.

As far as the condenser is concerned, I used a new style from Autozone. While it is not a true parallel flow type that ACKITS sells, it is the type that most the new R134a vehicles have. It has the 6mm tubes, more of them (48 instead of 36), and has a much different flow path through the core. It did make a pretty big difference when I put it in.

Thanks for all the advice, and keep it coming. I am trying to get this thing to work on a budget. I have already put way to much money into it, but once you go so far, it is hard to stop.

ChevyMan on Mon June 22, 2009 5:24 PM User is offline

I got my blue-board glued in place. I could tell a difference in the radiated heat immediately. I took some pressure and temperature measurements. It is 100 degrees here today. I measured 105 in front of the condenser. With the system on MAX and HI fan, the readings were as follows.

55 low
250 high

1500 RPM:
50 low
340 high

The vent temp was around 70 degrees. I would have thought 55-60 degrees for 50 psi. But, it was pretty hot in the truck. It had not had a chance to equalize. I did spray water on the condenser, but it mad only about 10 to 15 psi difference in the high side pressure. I feel that this indicates the fans and condenser are working.

I tried to calculate my oil loss when I changed the compressor and put back in the proper amount. If I put in too much, that could drive up the pressures, I suppose. I really can't think of anything else that would cause poor cooling.

fonebone on Tue June 23, 2009 1:28 AM User is offline

Hi ChevyMan; Something wrong somewhere! At 95 degrees on a previous road test you had 48 out the vents. You are now 70 degrees at the vents and only 5 degrees hotter?? Let's backtrack-- the last thing you did was change the compressor-- remember, you are putting in less R-134 than R-12. That also means less oil. Now things get critical. You say the system is not large enough for the vehicle. It would mean getting everything optimized near perfect. Looks like you might have too much oil. Your pressures are at idle--what about at road speed? Water test is interesting, shows little change. Anyone else here got any ideas???? I would go back to where you were close to optimum. Put the shroud back in, seal it good, put in your old clutch fan locked with the bolt and check pressures/temps. Remembering of course, you might be a tad over on oil.

ChevyMan on Tue June 23, 2009 12:23 PM User is offline

Last night I pulled off the electric fan and put the clutch fan back on. You guys are right. That mechanical fan draws way more air than the electric fan did. Like I said when I tested the pressures yesterday afternoon, I did not let the system have a chance to cool the truck. That, I believe is bringing the temps up a little. I was driving today around town. It's in the 90's. 45 to 55 degrees after the truck cools down, depending on the road speed.

I think you might be right. I just hate to flush it out again. That would be the only way to know the oil level. I guess I could take a chance and drain a little out of the accumulator.

fonebone on Wed June 24, 2009 1:17 AM User is offline

OK ChevyMan, looks like you are back on track! Take some more pressure readings, wet down the condenser again, and see what you get.If it makes little difference, then adding additional fans in front would be worthless. If you do not have the temperature /pressure chart for r-134, look for it here on site. If they are already overmaxed for the day's temp, then you could be a bit overcharged and/or have air in the system. Remember, being overcharged will raise both high and low side readings, and that just might be the problem. Evacuate a little at a time if you are way over on your high side pressures and see if the low side starts to drop. If the low side drops along with the high side, then your vent temps will drop also, indicating that you were overcharged. Have a digital temperature gage in the center outlet and monitor closely as you evacuate. Put an extra floor fan in front to simulate road conditions. Stop when you reach max pressure at ambient temp and/or it stops dropping temps in the vent. You then will have optimized the systems capacity. important-since you have changed the condenser and cannot add an exact amount as per a stock factory, unaltered setup. Keep us informed!

ChevyMan on Wed June 24, 2009 8:59 PM User is offline

Hi, there. I don't have any more pressure readings. Don't feel up to it today. I had to go to the ER last night with heat exhaustion. Anyway, I just went for a 30 mile drive. Starting temp was 140. It took 15 miles to cool to 50. In the next 5 miles, I turned the fan down one notch from high, and got down to 41 degrees. This first 20 miles was at 55 MPH. The next 10 miles were across town at 35 MPH and it warmed up to 43. Even then, it was just starting to get comfortable in the truck. I will play with the charge a little maybe, but I am wondering if that is all the BTU capacity of the system? I cant imagine that any electric fans would do any good with the stock clutch bolted and running 1500 RPM. It wants to suck the grille through the radiator. Then again, maybe I need the bigger fan from a one ton truck?

fonebone on Thu June 25, 2009 1:03 AM User is offline

Hi ChevyMan; Thinking over all you have done, I'm certain you are overcharged. Think about it. When you converted over to R-134, you put in a percentage of the factory r-12 volume. You are no longer at "factory" volume. It is said to start with this and go up, most of the time. You have changed to a 134 type condenser, and most, if not all have less "Volume" or capacity compared to your stock r-12 tube and fin condenser. My Chevy called for 3 and 3/4 lbs. of r-12 with the stock setup. When I changed to a r-134 style condenser, I'm only using 2 lbs. exactly to cool very nice. That shows you the difference in volume! That being the case, you would definitely be overcharged. I'm positive your system is fine, not under capacity to cool your truck. Work at getting your high side/low side pressures down to correct temps to ambient, and your vent temps will surely dip into the lower 40's and even the upper 30's. Also, though you have your bolted-up fan in there proving the concept that it is the most efficient setup, replace it with the Flex-A-Lite one I highly recommend. Sure, it will roar at low to medium speeds, but it will be slipping some, and at road speed, where air flow comes in, it quiets down a bit. You have to tolerate this. I'm betting this will optimize your system to it's max.

ChevyMan on Thu June 25, 2009 9:21 AM User is offline

I did not know about the condenser having that much less capacity. I will have to go play with it. As far as the fan noise, I don't mind that. You should hear the fan on the international big truck I drive at work. I was just looking for the fuel economy benefits that everyone seems to think you get by removing the mechanical fan. But for the short time I had the electric on there, I couldn't tell any difference. The AC compressor drags it down enough.

I think I will evacuate the system, drain a little oil out of the accumulator (not much though), and then recharge it. I called myself watching the temperature of the evaporator pipes, but I will try to pay close attention to not only that, but the vent temps also. Should I stop when the high side gets to 2.5 ambient even if the evaporator outlet is not as cold as the inlet. Will the truck being hot inside cause that, not just undercharged?

SpinRite on Thu June 25, 2009 9:50 AM User is offline

FWIW: Years ago I bought Bronco and the A/C couldn't keep it below 90 during the day, but it was fine at night.

It had a dark brown fiberglass top on the back half. This was in south Florida -- and that topper got so hot that you couldn't hold your hand against the inside of the ceiling. It was better to turn off the A/C and leave the windows open in the daytime.

So, I painted the top of it white (not the sides, just the very top -- you could hardly see it unless you were very tall) And -- Ba-da-boom! Ba-da-bing! -- that truck turned into a meat locker!

I couldn't believe how much difference that little bit of white paint made in the quality of life.

ChevyMan on Thu June 25, 2009 9:54 AM User is offline

I have already threatened to do that. The truck is a dark brownish color. I know that it must be soaking up a lot of heat. It made a big difference when I applied the insulation to the inside of the roof. Maybe a little white paint couldn't hurt anything.

fonebone on Fri June 26, 2009 1:37 AM User is offline

Hi ChevyMan; As for your 2.5 times the ambient during charging--this gives you a ballpark figure to look for. Performance is what I look for, and have found it works great when working on an altered sytem such as yours, where a factory charge now does not apply. Add the 134 after vacuum, continue to add slowly, pausing to let the system stabilize, say 30 seconds to a minute or so. Watching your high side gage as you add it in, monitor your cab temps at center vent using a digital gage that is easier to see small drops or rises in temp. You are not concerned with 80 percent at one shot, just go by performance, meaning not exceeding high side pressures for the ambient, while getting the vent temps down as far as you can. You will stop when vent temps will not go lower, which will be close to max pressures at ambient. If you go slow, adding a little at a time, you will see the vent temps basically bottom out and not respond to the last little bit you just added, because the digital gage reads in tenths, and shows even the slightest change quickly. Stop then, you are maxed out and at optimum. By the way, that white roof sounds great! Should reflect that sun and cool things, as we just read above. Do it, every little bit will help.

Edited: Fri June 26, 2009 at 2:50 PM by fonebone

ChevyMan on Sat June 27, 2009 5:47 PM User is offline

Ok, back at it again. I think I have it fixed now. Thursday afternoon, decided to adjust the charge a little. I can't remember the exact pressures now, but the static pressure indicated 110 degrees. It was about 95-98 outside, coupled with the extreme heat inside the truck, that seems about right. I started the system and let it come up to pressure. At 1500 RPM I was at I think 275 on the high side. I took a little out at a time till the high side came down to 250. The low side dropped maybe a little. Then I had to stop and tend to other bushiness. It seemed to cool off a little quicker.

I drove the truck this morning, at about 6:30 and I had 37 degree vent temp. After the 10 mile trip, I opened the hood and had ice on the inlet and outlet of the evaporator, and the suction line all the way back to the compressor. There was none on the accumulator. I am sure that I need to adjust the cycle switch a little. This afternoon, I painted the whole roof white. It is much more comfortable in the truck now. I had 43 degree vent and it is 95 and sunny.

fonebone on Sun June 28, 2009 1:16 AM User is offline

Hi ChevyMan; You are making progress--Excellent!! Keep us posted, we all like to hear success stories. That 50 plus differential from outside temps to vent temps shows you are on the right track.

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