[Racer X 69]

So your argument is basically "Everything you've experienced is wrong, and trust me because I say so."

You'll need to provide some documentation on this, because you are literally the only person I've seen mention this, and many others saying the opposite. If the a.c. keeps cycling, why have the option in the first place?

Since you also claim to have worked at PACCAR, I'll also add that I have been trucking 15 years. None of those cycled the a.c. when turned off either.

Here you go.

You Tube

You Tube

About every 15 to 20 seconds the clutch cycles on for a few seconds, then off. The A/C in the cab was switched off when this was happening. I replaced the compressor last year after the clutch failed. The truck has 140,000 miles on it, and I bought it new in 2001. This is how the A/C clutch has always behaved.


Again, every vehicle I have ever owned with A/C, and every vehicle I have ever worked on with A/C does this.


As for my experience, I served a 4 year state indentured apprenticeship and worked as a journeyman mechanic at an electric utility for 30 years, holding ASE Auto and Truck Master certification, air conditioning certification, Washington State Emissions Specialist certification, Mobile Fluid Power certification with the Fluid Power Society. Trained in steel and aluminum fabrication, and certified as a welder in oxy/acetylene, stick, MIG and TIG. Also attended many GM, Ford, Detroit Diesel, Cummins, International (engine, transmission, chassis, electronic controls) and Allison (transmission) schools.

After the power company I worked at PACCAR Technical Center at their product testing facility in Mount Vernon, Washington on a 6 month contract, on a team that helped to develop the PACCAR MX engine. After that I used my CDL (actually started as an A endorsement in the late 1970's, converted to the commercial driver's license in 1992 when the fitness for duty regulations changed how the licensing works) to get a job driving big trucks. In 5 years I covered 800,000 miles, drove to all of the lower 48 states and 6 Canadian provinces. Mostly flatbed work, flatbeds, stepdecks, double drops, curtainsides, conestogas, plenty of oversize loads, and mostly aerospace loads.

After 5 years on the road I took a job at Boeing in Everett, Washington as an aerospace machinist, and have had a hand in the manufacture of the Boeing 777-300ER, 777-200 freighter, 777-9, and am currently part of the team that builds the 767 freighter/KC-46 tanker. Been there seven and a half years now, and looking forward to retiring soon.

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Last edited by Racer X 69; 12-11-2021 at 10:16 AM.

[Racer X 69]

I probably shouldn't get caught up in this fray, but my Prius didn't do that. This was a special case for Toyota hybrids - because the engine could be off when using the A/C, it was electrically powered, not off the belt. Since it wasn't a common item, it was pretty expensive when I had to replace it after about 10 years of driving. a little more expensive than getting a refurbished battery pack (about $900) at the 13-year mark. Those were my 2 big items in the 15 years I owned it.

I must admit my only experience with a Prius was when the electric utility bought a couple for the fleet, all of us in the shop got to look at them, drive them a bit, and that was it. Toyota had a deal with the utility, prohibiting us in the vehicle maintenance shop from doing anything beyond checking and adjusting tire pressures, replacing wiper blades and light bulbs. All other service and repairs were required to be performed at the local Toyota dealer.

Being a hands on kind of guy, I would never want to own a car that I wasn't allowed to do maintenance and repairs on myself.

So other than the initial familiarization with them, I have very limited knowledge of the inner workings of one.

[Mooncatt]

Here you go.

A/C Compressor Clutch Cycling - YouTube


About every 15 to 20 seconds the clutch cycles on for a few seconds, then off. The A/C in the cab was switched off when this was happening. I replaced the compressor last year after the clutch failed. The truck has 140,000 miles on it, and I bought it new in 2001. This is how the A/C clutch has always behaved.

My current car, AC off and no cycling.

Youtu.be

Youtu.be

But to backtrack, this discussion stemmed from another on fuel economy. Running with the AC off, even if a manufacturer decides to short cycle theirs when off, is going to be more fuel efficient than running it (all else being equal).

[ThorSanchez]

But to backtrack, this discussion stemmed from another on fuel economy. Running with the AC off, even if a manufacturer decides to short cycle theirs when off, is going to be more fuel efficient than running it (all else being equal).

Except that we know that things are not usually equal, that people turn on the A/C to cool the car to a comfortable level. The only other option to do that is to open the windows, which negatively effects the aerodynamics of the car and its fuel efficiency.

So I agree that being very uncomfortable can be the most fuel efficient thing to do, but unless you're about to run out of gas and/or money that's not a reasonable option.

[ctt]

I’d like to be driving a Porsche or a candy Apple red 55 Chevy!

[CBM]

Except that we know that things are not usually equal, that people turn on the A/C to cool the car to a comfortable level. The only other option to do that is to open the windows, which negatively effects the aerodynamics of the car and its fuel efficiency.

So I agree that being very uncomfortable can be the most fuel efficient thing to do, but unless you're about to run out of gas and/or money that's not a reasonable option.

So, on a related note, when I am trying to stretch my highway miles between refueling stops on long distance drives, sometimes the next exit is either WAYYY further than I thought or didn't have a gas station sign (interstate, mostly along the fairly empty stretch north of Florida's Treasure Coast). Anyhow, I go into fuel conservation mode with 30 miles showing on the dash computer - which is less than a gallon actual - shut down the AC, slow down and cross my fingers! Haven't run out of gas...yet.

[ThorSanchez]

So, on a related note, when I am trying to stretch my highway miles between refueling stops on long distance drives, sometimes the next exit is either WAYYY further than I thought or didn't have a gas station sign (interstate, mostly along the fairly empty stretch north of Florida's Treasure Coast). Anyhow, I go into fuel conservation mode with 30 miles showing on the dash computer - which is less than a gallon actual - shut down the AC, slow down and cross my fingers! Haven't run out of gas...yet.

I've never had a car that actually ran out of gas at or around zero on the miles left indicator. Example, my old '05 Mini Cooper S. I went on a trip where I was supposed to get a rental car to the airport, Hertz was out of cars, so I drove the Mini. I was in a rush, and when I parked at Dulles it was showing zero miles left to empty. Got back, very tired, completely forgot, and drove 40+ miles before I remembered I'd been on empty. Stopped at the next station, but never ran out.

I think most cars have a gallon or more reserve when the indicator shows zero.

[lesmore49]

I've never had a car that actually ran out of gas at or around zero on the miles left indicator. Example, my old '05 Mini Cooper S. I went on a trip where I was supposed to get a rental car to the airport, Hertz was out of cars, so I drove the Mini. I was in a rush, and when I parked at Dulles it was showing zero miles left to empty. Got back, very tired, completely forgot, and drove 40+ miles before I remembered I'd been on empty. Stopped at the next station, but never ran out.

I think most cars have a gallon or more reserve when the indicator shows zero.

I ran out once on my '61 VW. No gas gauge, but did have a reserve lever under the dash. Just reached under, moved the lever to reserve, then drove a few miles , got some gas at a nearby station.

Also ran out of gas on my Czech made '65 Jawa motorcycle. Same deal as the VW, no gauge, but a little lever for reserve.

[ThorSanchez]

I ran out once on my '61 VW. No gas gauge, but did have a reserve lever under the dash. Just reached under, moved the lever to reserve, then drove a few miles , got some gas at a nearby station.

Also ran out of gas on my Czech made '65 Jawa motorcycle. Same deal as the VW, no gauge, but a little lever for reserve.

Did they have two tanks? Or something else?

My Dad had a 2nd tank installed in his '76 Chevy Cheyenne half-ton pickup. I think the primary was 20 gallons, which only got you maybe 200 miles at 9-10 mpg. So he had the dealer put in a second 30 gallon tank, with a switch under the seat to go between the two. The only time I've ever run out of gas was in that truck, but I didn't really because there was plenty in tank #2.

[lesmore49]

Did they have two tanks? Or something else?

My Dad had a 2nd tank installed in his '76 Chevy Cheyenne half-ton pickup. I think the primary was 20 gallons, which only got you maybe 200 miles at 9-10 mpg. So he had the dealer put in a second 30 gallon tank, with a switch under the seat to go between the two. The only time I've ever run out of gas was in that truck, but I didn't really because there was plenty in tank #2.

I'm not sure, whether it was 2 tanks or one, with some kind of arrangement/design to allow access to the reserve portion, of one tank. They (VW and Jawa) were both of central European manufacture (factories were not really all that far away from each other), and I think having a limited number of gauges, for entry level vehicles was not uncommon, back in those days. This was back in the 1960's.

I have a couple of older motorcycles, one an English made '67 Matchless 750 (similar to a Norton), the other a '78 Yamaha 500 single...both have no fuel gauge, but do have a trip meter, which I reset to ' 0 ' after each fill up. I monitor the miles on the trip odo, to determine when to fill up.

My son has a much later 2016, BMW G/S motorcycle, which has a factory fuel gauge.


I've always been a guy who regularly monitors all gauges for engine performance...and do like the newer gauge...which determines tire pressure in each tire, which I check ...cold pressure...immediately after engine start up. I run my tires with just a few pounds over recommendation, and compensate for colder seasons...ie. it will be -34 C tonight here, so our SUV...already has winter air (nitrogen) pressure.

BTW, my '61 VW didn't have a fuel gauge. That came as one of VW's little improvements in the 1962 VW Type 1. Or was it a running change that took place in later production '61 VW Type 1's ?

[Canada_Rockies]

Did they have two tanks? Or something else?

My Dad had a 2nd tank installed in his '76 Chevy Cheyenne half-ton pickup. I think the primary was 20 gallons, which only got you maybe 200 miles at 9-10 mpg. So he had the dealer put in a second 30 gallon tank, with a switch under the seat to go between the two. The only time I've ever run out of gas was in that truck, but I didn't really because there was plenty in tank #2.

My 1958 Mercedes 220S that I picked up in Germany in 1965 had a "reserve" pull tap. It was designed in the days of bad fuel in Germany, and was a second line from the pump to the tank, set a bit lower in the tank. It was partially for running out, and partially for getting plugged up.

[lesmore49]

So, on a related note, when I am trying to stretch my highway miles between refueling stops on long distance drives, sometimes the next exit is either WAYYY further than I thought or didn't have a gas station sign (interstate, mostly along the fairly empty stretch north of Florida's Treasure Coast). Anyhow, I go into fuel conservation mode with 30 miles showing on the dash computer - which is less than a gallon actual - shut down the AC, slow down and cross my fingers! Haven't run out of gas...yet.

I never run my modern day vehicles to almost empty.

[Canada_Rockies]

I never run my modern day vehicles to almost empty.

I've always maintained at least 1/4 tank of fuel. 1/2 in winter. It's a lot less expensive to pay a few pennies a litre more than pay for a tow.

[AgentL]

Except that we know that things are not usually equal, that people turn on the A/C to cool the car to a comfortable level. The only other option to do that is to open the windows, which negatively effects the aerodynamics of the car and its fuel efficiency.

So I agree that being very uncomfortable can be the most fuel efficient thing to do, but unless you're about to run out of gas and/or money that's not a reasonable option.

Or, in a relatively wet and chilly coastal climate, AC works to keep the warm air coming into your cabin drier than the outside air, which is better all around. I get pretty tired of moist air here.

[lesmore49]

I've always maintained at least 1/4 tank of fuel. 1/2 in winter. It's a lot less expensive to pay a few pennies a litre more than pay for a tow.

I'm similar. I rarely ever let my tank go below 1/2 a tank. I know many will drive till the low gas sign comes on in the dash.

Many manufacturers use fuel to cool the fuel pump, which in many vehicles nowadays is located in the gas tank. Low fuel can cause extra fuel pump wear. More details in the attached article.

I also used to ensure I didn't run the car, with very little gas in the tank...in the old days...as older gas tanks were made of metal and therefore could corrode, leaving some nasty debris at the bottom , which could be sucked into the fuel system, fuel filter and thereby cause problems in your fuel system.


https://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8...nZxj0EwUYjTCfO