# How to run a car compressor from mains

#### alchemizt

Joined Mar 23, 2021
24
I got this 12V car compressor:

which I want to convert into a vacuum pump. The issue is, its meant for connecting to a car battery, it has one of these car lighter plugs:

I need to run the compressor from mains, not from a car battery. I thought that wouldn't be an issue because I have a 12V DC power supply but now I realise this car compressor uses high amperage, 10A and the DC converter I have is only 1.3A.

10A is higher than any DC power supply I've come across. What would be effective and inexpensive way to run this car compressor from mains power?

#### MrSalts

Joined Apr 2, 2020
1,762
I got this 12V car compressor:
View attachment 262420
which I want to convert into a vacuum pump. The issue is, its meant for connecting to a car battery, it has one of these car lighter plugs:
View attachment 262421
I need to run the compressor from mains, not from a car battery. I thought that wouldn't be an issue because I have a 12V DC power supply but now I realise this car compressor uses high amperage, 10A and the DC converter I have is only 1.3A.

10A is higher than any DC power supply I've come across. What would be effective and inexpensive way to run this car compressor from mains power?
Pull a power supply out of a Desktop PC. Google: "ATX bench power supply". An ATX power supply should have at least 10A at 12v available.

#### MrSalts

Joined Apr 2, 2020
1,762
Or you can get a standard power brick AC/DC power supply.
It uses a DIN4 connector and prices jump pretty high as current goes up to meet your needs ($150 range). https://www.digikey.com/en/products...GgOSoKg4MhSggsNGIPIAAUiAB3XBcE6-RiMTAAT10wiAA The ATX power supply is cheaper but not exactly a standard use of such a device. You'll need a 10 ohm (10watt or 20watt resistor) resistor if your ATX power supply needs a minimum load to start up m Thread Starter #### alchemizt Joined Mar 23, 2021 24 #### MrSalts Joined Apr 2, 2020 1,762 I don't have any old Desktop PCs, and$150 for a power brick is way too much to run a $40 car compressor. They sell these 180W converters on Amazon for$35:
https://www.amazon.com/Acekit-Converter-Cigarette-Compressor-Refrigerator/dp/B07PQ9XY1N/

Another idea is to get a car battery and charger. I think the most practical solution is to return the compressor and get a different one
Or, you can just buy a vacuum pump. Running a compressor backwards is a terrible vacuum pump. Also, real vacuum pumps either pull a bit of a vacuum quickly OR, the pull a pretty good vacuum very slowly. Terrible vacuum pumps are really just aspirators that create suction like a vacuum cleaner (with a fan). Pressure difference is not great.

What purpose will this vacuum pump do? What absolute pressure are you hoping to achieve (and how fast)?

#### Ian0

Joined Aug 7, 2020
5,064
A car compressor will have a cheap brushed DC motor with a rated life of a few hundred hours if you're lucky. It's only intended for inflating tyres, and how often do your tyres go flat these days?
A mains compressor will have an induction motor and last for ages.

Joined Jan 15, 2015
6,581
Those pumps are not really designed for pulling a vacuum and designed for intermittent use. While the nameplate data does say 10 Amps I will venture at startup for a very brief period the pump will draw considerably greater current. This can be a problem in that if the load current exceeds what a power supply is rated for the PSU may shut down. I am seeing 12 Volt 30 Amp supplies for under \$30 USD on Amazon and haven't a clue as to their quality. You may also consider placing a large capacitio across the power supply to help with start current.

If this project is going to be permanent I would think about buying a pump designed for your application. It sounds like all you need is a vacuum roughing pump.

Ron

#### Tonyr1084

Joined Sep 24, 2015
6,884
Agreeing with air pumps are not vacuum pumps. All the 12V pumps I've seen have a piston and a valving routine that takes ambient air and forces it into the hose. Running the pump motor backwards will not cause a vacuum, it will still pump pressure no matter which way the motor runs. It's basically a diaphragm pump.

If you want a vacuum pump you need a more sophisticated machine. One that is designed to pull a vacuum. I happen to have a couple of those pumps. But again, running them one way OR the other still results in the same operation; the piston pulls air in from one port and reed valves direct the pressure out the other port. They ARE capable of pulling a small vacuum. In fact, I use one to suck the gasoline out of my lawn tools at the end of the season. I pull a vacuum on a tank then introduce the hose into the fuel tank and open the valve. The vacuum inside the tank pulls the fuel out. Then I pour the fuel into a gas can or winter equipment, then repeat. I have another tank I use for changing oil in the machines. A quarter inch tube does a nice job getting to the bottom of the engine. No need for lifting the machine up on bench or laying on the ground to open a drain plug.

One pump I came across was being thrown out by a glass blowing company. The switch had failed. So I cleaned it up. For the limited use I give it - it works fine. The other pump I have comes out of a Sun Engine Analyzer. Capable of pulling a vacuum to check engine hoses for leaks. I haven't pressed that into service yet, but it has a single AC motor and dual pumps, one on either side. I also have solenoid valves to control the direction of air movement. Trick, but as yet I haven't found a use for it. I might start using it this year as an aquarium air pump. I have it. No need to spend money. And it's a lot quieter than those vibrating diaphragm pumps that hum.

#### shortbus

Joined Sep 30, 2009
9,370
If you want a vaccum pump from a car you only need to go to the auto wrecking yard. GM had power brake assist pumps in many many cars over the years. Chose one from the Google search.

But most vacuum pumps we used at work were vane pumps not piston pumps.

Or you can buy one for 115V pretty cheap - https://www.surpluscenter.com/Air-P...-AC-Nitto-Kohki-Vacuum-Pump-VP0450-4-1961.axd

Or you can get the 12V model - https://www.surpluscenter.com/Air-P...Pumps/12-Volt-DC-11-HG-Vacuum-Pump-4-1831.axd

#### Ian0

Joined Aug 7, 2020
5,064
You’ll find them in diesels, because diesels have no vacuum in the inlet manifold, but I thought that they were mainly mechanical devices driven by the “fan“ belt.

#### alchemizt

Joined Mar 23, 2021
24
What purpose will this vacuum pump do? What absolute pressure are you hoping to achieve (and how fast)?
Right now it will be for vacuum filtrations. It would be nice to be able to use it for desiccating chambers and vacuum distillations in the future though. Both those applications are not so intermittant as filtrations.

I will definitely get a real vacuum pump when I find one for a good price, but for now all I have is the tire inflator.

I found an old car battery and am able to run the machine with this. All I need now is a charger for it

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#### MisterBill2

Joined Jan 23, 2018
11,874
I have experimented with trying to pull any vacuum with that type of compressor. Do not waste your time, it does not work That configuration of pump will require a machine shop to make a different cylinder, because they are only made to deliver pressure. But if you do try to do it, try it on 12 volts first to see if it does pull a vacuum, so you will save yourself the price of the power supply. AND the whole thing is very loud when it is running.

For an effective vacuum pump, the compressor from a discarded freezer or refrigerator can do very well. Even the very small one from a tiny ice maker. Cheaper to pul from a failed appliance, already runs on mains power, and much quieter.

#### shortbus

Joined Sep 30, 2009
9,370
You’ll find them in diesels, because diesels have no vacuum in the inlet manifold, but I thought that they were mainly mechanical devices driven by the “fan“ belt.
That may be so in your part of the world, but most diesels today use something called a "hydroboost" that gets it's power from the hydraulic power steering pump. Or the more modern yet electric power brakes. The vacuum booster I referenced earlier was for gas engines that don't make enough vacuum.

A hydoboost - https://www.autozone.com/brakes-and...jJg6P6zZd1Wv0tGcaRhoCSRYQAvD_BwE&gclsrc=aw.ds

#### bassbindevil

Joined Jan 23, 2014
419
There are venturi vacuum pumps that attach to water faucets; I think I've seen them used in chemistry labs (or at least in textbooks), and possibly in a book on DIY science equipment like the classic UNESCO publication, "700 Science Experiments for Everyone".

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#### MrSalts

Joined Apr 2, 2020
1,762
There are venturi vacuum pumps that attach to water faucets; I think I've seen them used in chemistry labs (or at least in textbooks), and possibly in a book on DIY science equipment like the classic UNESCO publication, "700 Science Experiments for Everyone".
Perfect for sucking dimethyl poopoo menidium vapor into the wastewater.

#### MisterBill2

Joined Jan 23, 2018
11,874
NONE of the suggested alternatives will be adequate or satisfactory.
And again, the construction of an automotive tire pump compressor prevents it from being converted to a vacuum pump. Most of them have no inlet check valve. Also, quite a few of the cheap mains powered compressors would be very difficult to use as a vacuum pump.

#### MrSalts

Joined Apr 2, 2020
1,762
NONE of the suggested alternatives will be adequate or satisfactory.
And again, the construction of an automotive tire pump compressor prevents it from being converted to a vacuum pump. Most of them have no inlet check valve. Also, quite a few of the cheap mains powered compressors would be very difficult to use as a vacuum pump.
None? Have you not read (or do you not understand?) what a laboratory aspirator is or how it works as suggested in post 14? "None" (in caps no less) is a very big declaration. Please correct it. Laboratory aspirators have been used for vacuum filtrations for the past 100 years. They can achieve a vacuum equal to the vapor pressure at the temp of the water used.

#### MisterBill2

Joined Jan 23, 2018
11,874
None? Have you not read (or do you not understand?) what a laboratory aspirator is or how it works as suggested in post 14? "None" (in caps no less) is a very big declaration. Please correct it. Laboratory aspirators have been used for vacuum filtrations for the past 100 years. They can achieve a vacuum equal to the vapor pressure at the temp of the water used.
I have used a laboratory aspirator and while it was OK for the experiment we were doing It would not be acceptable for any of my applications for a vacuum source since then. An aspirator requires a fair flow of water that must then be routed someplace. And iif for any reason the flow of water drops then it is very possible for the device that was being evacuated to suddenly draw a ot of water and ruin the experiment. I stand behind the validity of my comments!!.

#### MrSalts

Joined Apr 2, 2020
1,762
I have used a laboratory aspirator and while it was OK for the experiment we were doing It would not be acceptable for any of my applications for a vacuum source since then. I stand behind the validity of my comments!!.
Have you read how the OP plans to use the vacuum? Note, they are HIS uses, not your uses. HIS uses are all classic uses of a laboratory aspirators - since they are chemical/biological laboratory applications.

#### MisterBill2

Joined Jan 23, 2018
11,874
Have you read how the OP plans to use the vacuum? Note, they are HIS uses, not your uses. HIS uses are all classic uses of a laboratory aspirators - since they are chemical/biological laboratory applications.
I did read the description of the intended applications, and in each case the use of a water-operated aspirator is a really poor choice. My experience has been that with a fair volume evacuated, any disruption or disturbance of the water flow will allow the vacuum to pull water into the evacuated space very rapidly.
Perhaps your experience was different. THAT was my experience.

NONE of the TS anticipated applications would benefit from suddenly being flooded with water. Thus a water powered aspirator SEEMS A POOR CHOICE.
And also, it is not likely that the automotive tire filing compressor can be used to pull a vacuum.
There are a number of consumer grade medical devices that do include a pump that is easily adapted to vacuum pump operation. I suggest looking for a used one of those. They can quite nicely produce a vacuum suitable for solder removal as I have done.