Bullnose Enthusiasts Forum

A/C Noise In Big Blue

Classic

List

Threaded

39 messages Options

Gary Lewis

A/C Noise In Big Blue

Administrator

I have a noise in the A/C system that I'd like some help finding/diagnosing.

But I need to tell the backstory. Big Blue has a 1990 system in it with an FS10 compressor. It worked last summer but then as things warmed up this spring it wasn't cooling. Turns out the compressor had gone bad. After the shop installed a new compressor in late March I don't think I used it much as it was kind of cool out.

But on the trip to NM we used it some and it wasn't working well at all. So yesterday I took it back to the shop and they found that the condenser had a leak. After replacing it and recharging the system it cools fine but now there's a noise that can be heard in the cab but not in under the hood, as demonstrated in the videos below.

The mechanic and I are at a loss as to what it could be, but we fully agree that it only happens when the compressor is running and goes away when the A/C clutch is turned off. Janey and I drove it about 30 miles and at the end the noise was less pronounced, or we'd gotten used to it.

Any ideas what could be causing a noise like that?

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

85lebaront2

Re: A/C Noise In Big Blue

Administrator

It definitely sounds like compressor noise. Have either you or the shop tried the old screwdriver stethoscope trick? I was looking to see if the idler/tensioner was bouncing in the second video, it isn't.

What do the pressures look like? Are they reasonably steady or noticeably pulsing at lower rpm?

Bill AKA "LOBO" Profile

"Getting old is inevitable, growing up is optional" Darth Vader 1986 F350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 2009 Flex Limited with factory tow package Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413

Gary Lewis

Re: A/C Noise In Big Blue

Administrator

Haven't tried the screwdriver/stethoscope but may do that tomorrow and can put gauges on at the time time to answer that question. But I think I have a stethoscope that has a solid pickup so might use that instead of a screwdriver.

At times we do hear a little bit of a squeal under the hood that sorta sounds like the clutch may be slipping, but haven't pin pointed it. Maybe the stethoscope will.

Thanks.

Gary, AKA "Gary fellow": Profile

85lebaront2

Re: A/C Noise In Big Blue

Administrator

Three items:
(1) pressure too high will cause a fair bit of compressor "hum"
(2) pressure too high can cause the clutch to slip and squeal or chirp on engagement
(3) pressure too high can and will result in poor cooling

FWIW, I can darn near hang meat in Darth with twice the cabin area BB has, but, I did a fair amount of insulating under the carpet, on the firewall, and the 1996 doors have insulated cards or panels whichever term you prefer.

Bill AKA "LOBO" Profile

ArdWrknTrk

Re: A/C Noise In Big Blue

Administrator

In reply to this post by Gary Lewis

I watched both of your videos Gary.
It definitely sounds like the pump rather than the clutch but I suppose you'll know better if you listen closely with the stethoscope

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: A/C Noise In Big Blue

Administrator

Bill - I asked the guy if it could be overfilled. He didn't think so as they use a machine that reads the ambient temp, pressures, etc. But I'll check it tomorrow.

Jim - Thanks. It sounds like the pump to me as well, but I'm puzzled that you hear it in the cab and not under the hood. But maybe listening to it with a 'scope will tell the tale.

Gary, AKA "Gary fellow": Profile

Gary Lewis

Re: A/C Noise In Big Blue

Administrator

Looks like the pressures might be high. The video I took shows really steady needles, but the pressures look high to me.

The ambient temp was 77F and the humidity HIGH. Both doors were open and the fan on high. Didn't measure the discharge air temp but it was pretty cold.

On the left are the pressures soon after starting, about 46 and 250, and on the right are the pressures as the system got fully up to temp - 54 & 320. My table says at 75F we should be seeing 35-45 & 150-170 PSI. And at 100F we should be seeing 50-55 & 315-325 PSI, which is right where we are.

I also used my stethoscope with a solid probe and cannot find that sound under the hood. The compressor has noises but not really that one. And the receiver drier and evaporator have noises but they don't change with RPM and the one in the cab sure changes with RPM.

So is it pressure?

Gary, AKA "Gary fellow": Profile

85lebaront2

Re: A/C Noise In Big Blue

Administrator

Gary, the low side definitely seems a bit high. First what condenser are you using? Darth has a 1994-1997 gas engine one. Second, what orifice tube is in it and what evaporator core (again I have the 1994-1997 one). Third, accumulator, when Darth is running the accumulator frosts up on low fan, but will go to just wet on higher speeds. Discharge temp is around 40° F at low fan (remember humidity here can hit 100%) climbing to maybe 65 at high fan. I test with a large fan blowing on the front of the vehicle to simulate driving speed.

Bill AKA "LOBO" Profile

ArdWrknTrk

Re: A/C Noise In Big Blue

Administrator

In reply to this post by Gary Lewis

Glad to find out it isn't the new compressor!

Have you tried climate control 'fan' without the compressor on?
It seems odd to be the sound would be in sync with engine rpm, but I guess it's possible.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: A/C Noise In Big Blue

Administrator

In reply to this post by 85lebaront2

Bill - The receipt shows "7-4150" which I take to mean they put in a Spectra Premium 7-4150 and Amazon says that's the right one for a 1990 system. And I have a red orifice tube in. The evaporator is from a 1990, and the accumulator is for a 1990.

Perhaps I just didn't have enough air flow? I don't think the fan clutch had engaged at that point, but I'm not sure. I don't have a large shop fan for that but the hood was open.

Jim - The fan doesn't have that noise by itself, and the noise comes and goes with the A/C compressor's clutch coming in/releasing regardless of fan speed.

I have a call into the mechanic and we'll see if he wants me to bring it in.

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: A/C Noise In Big Blue

Administrator

Gary Lewis wrote

Jim - The fan doesn't have that noise by itself, and the noise comes and goes with the A/C compressor's clutch coming in/releasing regardless of fan speed.

Interesting...

But you hear it coming from the ductwork and not under hood.
I have to wonder if the evaporator coil is somehow transmitting the noise.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: A/C Noise In Big Blue

Administrator

Right - ductwork and not under the hood. Or, maybe "from the dash" would be more correct as I can't really pinpoint where it is coming from.

However, when I put my stethoscope on the fittings of the evaporator I don't hear the noise. I do hear a noise that is similar but it doesn't vary by RPM like "the noise" does.

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: A/C Noise In Big Blue

Administrator

. Maybe the ghost of

is kicking and screaming as you try to evict him from Big Blue?

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: A/C Noise In Big Blue

Administrator

LOL!

Well, I'd really like to be shed of him so I might be willing to live with the noise if that's what it takes.

Heard back from the shop and we agreed to wait until Janey and I get back from our upcoming trip to see the kids before worrying about it. I reported what I'd found, both the pressures as well as lack of finding the source via the stethoscope. And I explained that since I don't have a fan to blow through the radiator and I don't think the clutch on the cooling fan had kicked in that maybe the pressures aren't really high?

Anyway, we are on hold.

Gary, AKA "Gary fellow": Profile

85lebaront2

Re: A/C Noise In Big Blue

Administrator

In reply to this post by Gary Lewis

To quote my Spectra Premium parts guy (at the time I was updating Darth) he recommended the 7-4531 which is for the 1994-97 trucks and the 0233091 accumulator. I already had the 1996 evaporator and the 1990 FS10 compressor. I scored a 1996/7 set of lines at Pick-n-Pull VB and I have the largest orifice tube as that is what is recommended for a crew cab.

I purged the compressor and replaced the oil with PAG then evacuated and charged with R134a

The condenser is described as a multi-pass and is not cleanable if I lose a compressor.

I still think what helped the most in Darth, other than using the complete later system is the thermal barrier insulation under the carpet with a double layer over the exhaust pipe area.

Bill AKA "LOBO" Profile

Gary Lewis

Re: A/C Noise In Big Blue

Administrator

Yes, the 7-4531 does appear to fit the later trucks. I hope I don't have to do this again, but if I do I might go that way. But it takes different lines?

I, too, have insulation under the carpet as well as in the roof, plus on the A/C system. So I'm pretty sure it'll do the job - assuming it has quit leaking.

Gary, AKA "Gary fellow": Profile

Gary Lewis

Re: A/C Noise In Big Blue

Administrator

BRRRR! Just took the truck on a drive to see what the discharge temps are. And I'm chilled!

This was in Max mode where it is pulling inside air and the vacuum switch is shutting off any water to the heater. The ambient is 82F with 74% humidity. Here are the readings with the fan speeds:

High: 42 to 52, with it staying on 42 for a long time

#3: 42 to 52, but less time on 42

#2: 44 to 54, but this was early in the trip

#1: 38 to 52, but this was at the end of the trip when the air in the cab was COLD!

After a few miles the air blowing on my arms was downright chilly. I think this thing is WORKING! But it still makes a bunch of noise.

Gary, AKA "Gary fellow": Profile

85lebaront2

Re: A/C Noise In Big Blue

Administrator

Sounds like it is better.

Bill AKA "LOBO" Profile

AmericanSavage

Re: A/C Noise In Big Blue

In reply to this post by Gary Lewis

Gary,

Off topic: I like that RPM gauge in the center you have. Mine is blank—never had one. Is there a way to add one, and what might that entail? New soft circuit board on the back? And where would someone fine a gauge to fit?

Cheers!

1980 Ford XLT F350
400 Engine (rebuilt to 406)
Holley 2300 500 CFM manual Choke Carb
Under Restore (1st time)

Gary Lewis

Re: A/C Noise In Big Blue

Administrator

In reply to this post by 85lebaront2

It cools really well, but it is still noisy.

As for tachs, you might want to read the page at Documentation/Electrical/Tachometers. But there's a piece of info that appears to be lacking on that page. If your truck has gauges then the wiring harness is there for a tach. But if you have idiot lights you are basically out of luck. Not only is your truck not wired for the tach, but it doesn't have the needed wiring for the other gauges either and you can't install a cluster with gauges.

Assuming you have gauges then you need to check to see if your instrument cluster's printed circuit supports the tach. From our page at Documentation/Electrical/Gauges comes the table below for printed circuits. But it is confusing. So the best thing to do is to pull the cluster out and see what you have. If your printed circuit has copper tabs where the four studs go for the tach then you are in. If not, it'll have to be replaced.

And the best way to replace it is to buy a cluster with a tach in it. If you have gauges it'll bolt/plug right in.

Gary, AKA "Gary fellow": Profile