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Broomwade AC10 compressor question

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I think I have a pressure switch problem – condor mdr3/16 on an AC10

by john
(cumbria uk)

broomwade ac10 and gec 2.2kw motor, 125l,single phase 230v, 1977 vintage uk

Broomwade AC10 air compressor
Broomwade AC10 air compressor

hi, the question is two fold and one could be the cause of the other,

I recently bought a decent ac10, it still had the original decomp valves in the heads and the guvnor, it was suggested to bring it into the 21st century as a new pressure switch was needed.

the de comp valves and guvnor were removed and the heads were sealed with 3/8th bsp bolts the feed to the tank from guvnor was removed and sealed with a 1/4 bsp plug as none of these were needed anymore.

the compressor has a new condor mdr3 switch with built in unloader valve and a pipe connected to the top of the nrv as with modern compressors, the nrv works and is in good condition.

when the comp is switched on it will build up pressure to around 120psi though can vary and the switch will cut power as it should and a brief hiss of air out of unloader, as it should, the pressure switch has auto and off via front switch,

i think it should back off a little ready to come back on when pressure is used at a certain psi, it does not do this when it cuts out it switches off so therefore does not cut in at lower pressure.

any instructions for mdr3 are very vague to say the least, i.e how to wire it up, a sparky friend couldn’t understand it too well either it is as follows earths are self explanatory so wont include them. live and neutral from mains doesn’t tell you which is which, so we did it this way,6 connections, live to no1 through to no2 to motor, neutral to no3 through to no4 looped round to no6 from no4 and through to no5 and then to motor, for clarity nos 1,3,5 on one side and 2,4,6 on the other, would this be the reason switch doesn’t function as it should, I’ve already returned one thinking it was faulty that did the same thing, i would think unlikely with two or has mdr 3 have some hidden switch i dont know about

ideas much appreciated, i am aware that it could be simple.


mdr3/16 wiring
by: Doug in s.d.ca

Yeah, this is kinda strange, to me.

Are you M1JWR on mig welding ?

Have you tried neutral on 1, and hot on 3?

You don’t have an SK- anything?

“i think it should back off a little ready to come back on when pressure is used at a certain psi, it does not do this when it cuts out it switches off so therefore does not cut in at lower pressure.”

Possibly, switching the input power will change/fix this.

Let us know, please.


by: M1JWR

Hi yes on mig welding.

thanks for the suggestion, i have now done this, it just does the same i’m afraid,

i watched a compressor at work its much newer but appears to have the same switch on it, it cuts out at say 120psi and when it goes down to around 80/90 psi it cuts back in etc etc

the knob stays vertical, dosent move when its doing this

betcha its gonna be somthing silly and simple and a “i shoulda thought of that moment”
thought i would ask to a wider audience !!


by: john

thanks for comment, yes on mig forum, thought i would put it to wider audience!!

comp at work is on a drive through wash and is working 24/7.

there must be something else to activate and i dont know what it is, i wish condor instructions were better, whats the sk thing ?


Switch turns off
by: Doug in s.d.ca

…is that what you’re saying? Physically moving itself to “off”? Need to get that clarified.

Swapping the hot/neutral had no effect?

Have / can you get into the one at work to see if it’s the same as yours?

Is your switch positioned such that it “sees” the pressure in the tank, as opposed to the line from the pump?

After it turns itself off, can you turn it back to auto, and does it then cut-in as expected?

The “sk thing” is related to add-in components referenced on condor’s on-line spec sheet.


by: john


yes when it reaches pressure around 90/100 psi the switch knob flicks from vertical (auto) back to 9 o’clock (off) at cut out,

havent yet tried switching it back on again manually at that point.

cant really look at the one at work, compressor is a bit up a height and is a 3 phase system in there anyway.

there are some pics on mig welding under ac10 post that you can see where switch is, pressure meter is on same outlet just above switch.

all the old valves and guvnor are off now just the thin pipe that goes from nrv at opposite end to unloader at switch.

regards john


by: john

cracked it, had to be something silly, when its up to pressure switch it on again, why cant condor put in instructions for the average joe.

i didn’t look at it that way as faulty one kept putting more pressure in 30 to 50psi at a time until danger valve blew off.

in the case of this one if its not up to pressure it will do the same – haven’t risked how far, i would assume another 100psi, i don’t know, so initially at first switch on it will go up to 100/110psi then cut out and switch off, then switch back on manually, it wont restart

use air to around the 80’ish psi area and then will cut in and cut out at 100/110 again etc.
thanks doug your suggestion came good


nrv condor mdr3/16
by: Doug in s.d.ca

OK, reviewed all the posts and pix. You’ve added a nrv with an unloader port, but I don’t see where.

Either another pic or describe where the nrv is, please.

I guess you can put the pic on migwelding, if it’s easier.

By the way, for those keeping score at home, the other post and pix are at


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