A/C Noise In Big Blue

[AmericanSavage]

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.

Hey Gary,

Thank you. No idiot lights in my dash. Sorry to ask the out of context question. I know one day I will be tearing into my plenum again as I removed the guts of my a/c. Cheers!

[Gary Lewis]

Hey Gary,

Thank you. No idiot lights in my dash. Sorry to ask the out of context question. I know one day I will be tearing into my plenum again as I removed the guts of my a/c. Cheers!

No problem, we don't worry too much about chasing rabbits around here. And if you have gauges you can have a tach. It may be as simple as adding the tach itself to your instrument cluster if your printed circuit has support for it, or changing the cluster out for one with a tach.

[Gary Lewis]

Sounds like it is better.

Time to close out this thread - SUCCESS!

Janey and I took Big Blue on a 150 mile jaunt yesterday and the A/C noise was just as obnoxious at the end as at the start. And it was really OBNOXIOUS.

But I noticed that on bumps the sound changed a bit, almost sounding like the A/C compressor was loose. So today I started looking the A/C system over to see if anything was loose and I spotted something suspicious. In the pic on the left you can see that the aluminum can, which I think may be a filter but I can't find in any illustration of the A/C system, is touching the brake master cylinder. In the pic on the right it has been isolated from the M/C by a very fancy item - 4 layers of bicycle inner tube rubber. And the noise is gone!

Apparently the filter was transmitting the sound of the A/C compressor through the M/C and booster and into the firewall, which explains why I couldn't figure out where it was coming from.

Anyway, the problem has been solved and I'll come up with a more elegant solution to keep the two components from touching.

[85lebaront2]

Time to close out this thread - SUCCESS!

Janey and I took Big Blue on a 150 mile jaunt yesterday and the A/C noise was just as obnoxious at the end as at the start. And it was really OBNOXIOUS.

But I noticed that on bumps the sound changed a bit, almost sounding like the A/C compressor was loose. So today I started looking the A/C system over to see if anything was loose and I spotted something suspicious. In the pic on the left you can see that the aluminum can, which I think may be a filter but I can't find in any illustration of the A/C system, is touching the brake master cylinder. In the pic on the right it has been isolated from the M/C by a very fancy item - 4 layers of bicycle inner tube rubber. And the noise is gone!

Apparently the filter was transmitting the sound of the A/C compressor through the M/C and booster and into the firewall, which explains why I couldn't figure out where it was coming from.

Anyway, the problem has been solved and I'll come up with a more elegant solution to keep the two components from touching.

I don't have a muffler (what you are calling a filter) on Darth, but I am using a set of 1996 AC lines, I also do not have the Hydro-boost which may set the MC further forward. Good thing you found it, the aluminum muffler would have worn through eventually.

[Gary Lewis]

I don't have a muffler (what you are calling a filter) on Darth, but I am using a set of 1996 AC lines, I also do not have the Hydro-boost which may set the MC further forward. Good thing you found it, the aluminum muffler would have worn through eventually.

That may well be a muffler. It doesn't show in the '85 nor '95 FSM, but there's a filter at about that spot that the '95 version says can be added down the road if you have a compressor failure. So I thought it might be that.

And yes, it would have eventually worn through. But in the interim it was causing me no end of consternation!

Apparently the new condenser's line is just a bit longer than the old one and it puts that muffler up against the M/C, which is the F450 M/C and it is probably longer than that of a 250/350. Plus the hydroboost moves it farther forward as well. Whatever, the combo doesn't play very nicely together.

Monday I'll call the shop that did the work and explain what the problem is/was. They need to know that having things like that in contact with things like the M/C is going to cause noises that are hard to find. I'm not upset, just want them to know so they can keep from doing that in the future since they were totally at a loss as to what could cause that noise - a noise they agreed shouldn't be there.

[ArdWrknTrk]

Time to close out this thread - SUCCESS!

Janey and I took Big Blue on a 150 mile jaunt yesterday and the A/C noise was just as obnoxious at the end as at the start. And it was really OBNOXIOUS.

But I noticed that on bumps the sound changed a bit, almost sounding like the A/C compressor was loose. So today I started looking the A/C system over to see if anything was loose and I spotted something suspicious. In the pic on the left you can see that the aluminum can, which I think may be a filter but I can't find in any illustration of the A/C system, is touching the brake master cylinder. In the pic on the right it has been isolated from the M/C by a very fancy item - 4 layers of bicycle inner tube rubber. And the noise is gone!

Apparently the filter was transmitting the sound of the A/C compressor through the M/C and booster and into the firewall, which explains why I couldn't figure out where it was coming from.

Anyway, the problem has been solved and I'll come up with a more elegant solution to keep the two components from touching.

Glad you found it!

Especially glad that the MC haven't rubbed a hole in the AC canister.

Though I'd watched your videos I certainly couldn't tell that the sound was coming from the brake booster into the cab.

Do you think there is enough room in the mounts to shift the line? Or is there another application that doesn't have that can in the same place?

[Gary Lewis]

Glad you found it!

Especially glad that the MC haven't rubbed a hole in the AC canister.

Though I'd watched your videos I certainly couldn't tell that the sound was coming from the brake booster into the cab.

Do you think there is enough room in the mounts to shift the line? Or is there another application that doesn't have that can in the same place?

Yes, I'm very glad to have found it. It was driving me bananas as it was directly tied to the compressor's RPM, going away completely when the compressor shut off and coming back instantly when it came on. And in town it was LOUD. I'm sure it was just as loud at speed, but there is so much more noise that it wasn't as intrusive.

Like you, I would never have guessed the sound was coming in via the brake master cylinder/booster combo. I really thought it was coming in via the vents, but if you listened to them you couldn't tell for sure. Obviously now that's not where it was coming from - it was the whole firewall!

But I don't want to change out the lines as they were expensive and would require re-charging the system. So I'll see if I can bend something or reroute things to get that part away from the M/C. Maybe just tweaking the tube going into the condenser will do it?

[ArdWrknTrk]

Yes, I'm very glad to have found it. It was driving me bananas as it was directly tied to the compressor's RPM, going away completely when the compressor shut off and coming back instantly when it came on. And in town it was LOUD. I'm sure it was just as loud at speed, but there is so much more noise that it wasn't as intrusive.

Like you, I would never have guessed the sound was coming in via the brake master cylinder/booster combo. I really thought it was coming in via the vents, but if you listened to them you couldn't tell for sure. Obviously now that's not where it was coming from - it was the whole firewall!

But I don't want to change out the lines as they were expensive and would require re-charging the system. So I'll see if I can bend something or reroute things to get that part away from the M/C. Maybe just tweaking the tube going into the condenser will do it?

Maybe!

I couldn't say, as this truck has never had AC or Hydro boost.

I do know a thing or two about bending aluminum tube but never tried it in place and under pressure.

[85lebaront2]

Yes, I'm very glad to have found it. It was driving me bananas as it was directly tied to the compressor's RPM, going away completely when the compressor shut off and coming back instantly when it came on. And in town it was LOUD. I'm sure it was just as loud at speed, but there is so much more noise that it wasn't as intrusive.

Like you, I would never have guessed the sound was coming in via the brake master cylinder/booster combo. I really thought it was coming in via the vents, but if you listened to them you couldn't tell for sure. Obviously now that's not where it was coming from - it was the whole firewall!

But I don't want to change out the lines as they were expensive and would require re-charging the system. So I'll see if I can bend something or reroute things to get that part away from the M/C. Maybe just tweaking the tube going into the condenser will do it?

Gary, I can't really see why they are anywhere near your master cylinder. Here are some pictures of Darth's AC lines in that area:

[Gary Lewis]

Gary, I can't really see why they are anywhere near your master cylinder. Here are some pictures of Darth's AC lines in that area:

Bill - Remember that I have a 1990 system, not the later system that you have. The original hoses, aka manifold set, that I got from Huck had that "muffler" in the same spot as the new hoses/manifold that I had to buy to replace the leaky one. And it has it in the same spot, right up against the M/C.

As I said, the 1995 FSM doesn't show anything in the hose line at that spot, nor does the 1985. So it must be something with the 1990 system that I have.

I'll take some more pics, although it may not be until Monday as I'm not sure what the plans are for Father's Day. But there has to be a way to change things just enough to have clearance there.