I first used the skoda-supplied electric tyre inflator on my 6-month old car about a week ago. If not connected to a tyre, it runs fine from any 12V socket on the car. If I connect to a tyre and then attempt to run the inflater, fuse 40 blows instantly. This is repeatable until my stock of 20A fuses runs out 🙂. The manual does not specify what fuse is required in position 40, but what I originally removed was 20A. Does anyone know where there is a table of fuse ratings for the Superb, just in case the issue is an incorrect fuse rating?

 

I had explained the issue to my dealer, who wanted to have the car for a day to diagnose this fault. I said that I thought it was most likely a defective inflator, so they kindly loaned me one. The fuse still blows. The steady state current drawn by the inflator is about 7-8A. Any surge is too brief for me to measure. Anybody had this experience or got any thoughts about how to cure it? It's quite annoying to think that a piece of equipment primarily for emergency use is not trustworthy.

 

 

3 hours ago, ChristopherMo said:

It's quite annoying to think that a piece of equipment primarily for emergency use is not trustworthy.

 

No ****.

 

I don't have a spare, either. I do carry a foot pump, though. Very useful for keeping my tyres at 36psi, never needed it in anger...

 

Yet...

Quote

If not connected to a tyre, it runs fine from any 12V socket on the car. If I connect to a tyre and then attempt to run the inflater, fuse 40 blows instantly.

 

Have you tried to to connect the inflater before you screw it to your valve/tyre. It could just be the motor in the inflater is stalled because of the back pressure on the compressor/piston?

regards retiredbri

@retiredbri - what you say makes sense. It somehow seems wrong to have the inflator running prior to screwing it into the tyre, especially since that is a fairly clumsy part of the procedure already. Assuming you are right, it suggests that the motor in the inflator just doesn't have enough torque. I can't try this in practice at the moment as I'm down to my last 20A fuse. I think I might let the dealer take a look, particularly as I'm sure I saw that look in the eye that says a mixture of "Aah, bless!" and "Where do these idiot customers come from?" from the techie when he gave me the loaner.

12 hours ago, retiredbri said:

 

Have you tried to to connect the inflater before you screw it to your valve/tyre. It could just be the motor in the inflater is stalled because of the back pressure on the compressor/piston?

regards retiredbri

Surely there will be a NRV/ Check valve to prevent this. Maybe it’s stuck open.

Edited 22 September, 20196 yr by Kenny R

What kind of connection does your pump have? Is it a push-on or screw-on or latch-on? Are you tightening up fully (for screw-on) or pushing on the coupling fully (latch-on/push-on) sufficiently to compress the valve core to allow air to flow into/out of the tyre? When connected with compressor switched of you may hear air hissing back out of the tyre, though that will only happen if there isn't a non return valve. If no air can flow as retiredbri said the compressor will have stalled /air-locked. 

Edited 22 September, 20196 yr by Gmac983

@Gmac983 Screw-on connection, which I screwed up fully before starting the inflator. You need to screw it on fairly quickly because mid-way quite a lot of air starts to leak from the tyre.  Once it's fully connected, there is no air  leaking obviously (although a small leak must be present as over time it is possible fully to deflate the tyre - i discovered this while investigating where the fuse is, the first time this happened). During "normal" use, on a well-inflated tyre the back pressure appears to be enough to stall the compressor motor, even if the valve is open.

Hmmm... All very odd... And you say that the lowned dealer pump does the same? Don't suppose you have access to another vehicle to try the pump(s) on, your own pump and the dealers lowned one. Or a willing volunteer/victim😁 who'll let you use their car to try it (at the risk of blowing their fuse as well!?). By the sound of things you might just have to bite the bullet and let the garage have the car to do a diagnostic. Have you any other different 12V devices/gadgets to try out? 

Just a thought and I'm totally clutching at straws here but did you have the engine running while you were running the pump, it shouldnt really matter a hoot as far as the cars aux 12V circuit is concerned but I think from memory the instructions state to have the engine on whilst using these emergency puncture repair pumps. 

Edited 22 September, 20196 yr by Gmac983

Sounds like the compressor is of a bad design. I'm willing to bet if you let your tyre down to 5 PSI before connecting it up it would pump it up happily to 30+ without stalling.

That is a possibility SuperbTWM... I'm assuming it's the standard VAG emergency pump that he has rather than an aftermarket one, since his dealer loaned him one the same. I had one with my octy vRS years ago, only used it the once in Conjunction with the foam for a puncture which actually turned out to be a cracked wheel as well so the emergency repair didn't work in my case and the pump never had to build up any pressure. Ended up limping the couple of miles home on the flat (wheel and tyre where ruined by this point anyway). Typical that it would happen on the only car I've had with no spare or run-flat tyres. 

Sounds like a faulty compressor, have used mine once (actually a friend used it) and it works fine, looks the same unit as was in my wife's A2s many years ago and its spare had to be inflated to about 60 psi.  It won't be made by VAG.

 

I tend to use an "old" Honda compressor that I forgot to put into the boot when a previous company car was returned so I don't need to stow the lead and hose when I finish.

 

The trick when connecting the compressor is to screw it on until you start hearing air escape, then press the hose towards the valve.  This should stop the air escaping while you finish tightening it up.  Removing you push the hose towards the valve until you have unscrewed it sufficiently to stop air escaping when you release it. 

Interesting thoughts, everyone. Given that two different units behave pretty much identically, I am inclined to think it's poor design of the inflator. I'll let the dealer take a look at the car. Unless the car's electrical circuit includes a surge suppressor, which has subsequently failed, it seems completely unlikely that the car itself is the cause. I'm sure I'll get all kinds of mumbo-jumbo from the dealer, so I'll report the high- and low-lights here.

 

43 minutes ago, ChristopherMo said:

I'm sure I'll get all kinds of mumbo-jumbo from the dealer, so I'll report the high- and low-lights here.

It's good to have realistic expectations!

I look forward to hearing their ideas.

They should at least be able to confirm whether the 20A fuse value is correct, which no-one has corroborated for you so far I don't think? As an experiment, not to be left in permanently, why not try a 25A fuse and see if that does the same?

 

On 24/09/2019 at 08:01, IJWS15 said:

Sounds like a faulty compressor, have used mine once (actually a friend used it) and it works fine, looks the same unit as was in my wife's A2s many years ago and its spare had to be inflated to about 60 psi.  It won't be made by VAG.

 

I tend to use an "old" Honda compressor that I forgot to put into the boot when a previous company car was returned so I don't need to stow the lead and hose when I finish.

 

The trick when connecting the compressor is to screw it on until you start hearing air escape, then press the hose towards the valve.  This should stop the air escaping while you finish tightening it up.  Removing you push the hose towards the valve until you have unscrewed it sufficiently to stop air escaping when you release it. 

 

When I said "standard VAG pump" I thought I fairly obviously meant standard VAG supplied pump. 

OP stated that he has tried 2 identical pumps with the same results (what's the chances of both pumps being duff). 

As someone else here said, maybe try the pump on a flat(ish) tyre and see what happens. As the pump is designed for emergency inflation with foam (after injection) perhaps said pump just does not have enough guts to further inflate a Tyre that is almost fully inflated already. 

Although in the interests of science I really should deflate my tyre and see how the inflator copes, I am disinclined to do this mainly because another failure would have me asymmetrically exercising my leg muscles (again)  It is disappointing, although not surprising, to imagine VAG paring the spec on this item to the bare minimum. Perhaps it's time to cut my losses and buy a better-designed third-party unit. This, however, raises the question of how to validate the performance of such a device before I have actually purchased it.

Hi all

I've got the pump that was included in my 2016 Superb. I've tested it by plugging it into the boot 12V socket (engine not running). Turned pump on and it ran fine. Covered nozzle with my finger (inside a thick rubber glove) and the pressure went up immediately to 30+ psi. No overload, no fuses blowing. Repeated it with nozzle covered before switching on and same result. Didn't have a current meter.

The pictures show the details of the pump.  Hope this helps. 

ChristopherMo:

Shop around for one on Amazon or eBay, somewhere with a few unbiased reviews, at least then you might have rough idea if what your looking at is any good. 

I have a hunch that there is still something a miss here yet to be found out. Is your pump(s) the same as retiredbri's one above? 

 

retiredbri:

Yep that looks pretty much like the emergency pump that's usually supplied within VAG. I assume you have the foam canister Included in your emergency kit as well?

 

Hi, mine has the sealant but it expires in 2020.
I had a pump from my previous car, It works fine and has the benefit of a Thumb Lock Lever Connector (much better then screw connectors that loose air when screwing on an off)
It was a DBPOWER 12V DC Portable Electric Auto Air Compressor Pump to 150 PSI, Tyre Inflator with Gauge, 3 High-air Flow Nozzles & Adaptors for Cars, Bicycles from Amazon. See the reviews for this and similar.

The one pictured looks pretty much identical. I can't imagine what kind of fault in the car would cause this fuse blowing issue, other than 1) something else drawing substantial current at the same time; 2) substantially higher voltage than expected from the battery (the alternator is not running at this time); 3) malfunction from some unknown device in the circuit internal to the car that is there to suppress transients. None of these sounds remotely likely, frankly. 

 

Measuring dc resistance between the contacts of the lighter plug of the compressor might be interesting, on a known-good and a known-fuse-blowy pump; ideally with the same meter.

 

I think that might give a broad-brush idea of the expected stall current (current drawn when initially at ambient temperature, and not able to rotate) of the motors in each (I=V/R). I suspect though that the numbers for the fuse-blowy pumps will be hard to measure accurately with a normal meter. To blow a 20A fuse rapidly means the drawn current is probably in excess of 50A, so the cold resistance must be (R=V/I=12.5/50 = 0.25 Ohms approx.)

 

Even a significant resistance difference between what's measured on a known good pump versus a 'problem pump' could be useful though. Not going to be easily comparable with different meters, and probe lead resistance will need to be subtracted if there's any >0 number shown when the probe tips are shorted together.

 

 

 

Hmm ... measuring 0.25 Ohm accurately and precisely with any practical instrument that I possess sounds like a non-starter!

Doesn't need to be accurate or precise, just noticeably lower than one that doesn't cause the car problems. 

20 hours ago, Wino said:

Doesn't need to be accurate or precise, just noticeably lower than one that doesn't cause the car problems. 

Mine is 2 ohms (measured with a reasonable muli-meter.

retiredbri

20 hours ago, retiredbri said:

Mine is 2 ohms (measured with a reasonable muli-meter.

retiredbri

That indicates a 6amp current draw but with motors such as a compressor that will change under load.

 

Manufacturer indicates a maximum current draw of 15amps, see here: https://aircom.ag/tire-air-compressors/

 

Have you any after market items installed? Dashcam, towbar, heater?

 

I would look to see the nominal load on the circuit before the compressor is attached, there is only 5amps of head room before the fuse could blow. Also a person with a bench power supply will be able to tell you how much current the compressor is actually drawing under load. The current will also depend on your battery voltage, the lower the voltage the higher the current will be.

No other items on the circuit in question. I measured the steady-state current when the inflator was running (free of a tyre) and it was 7-8A (which is about right according to the rating plate). It is clearly the starting current when attached to a tyre that does the dirty. Incidentally, I don't think you are correct about fuse rating and headroom. Any fuse is rated for its steady-state capacity and it will tolerate a substantial overload for a time, the magnitude being higher if the overload is shorter. Since the fuse here is blowing in less than a second, I presume the load is anything up to 50A (as someone earlier suggested).  Lower battery voltage would cause lower current (V=iR) assuming that there is no clever device within the pump to guarantee constant power (and I'd be astonished if there wer!)