Help find this part!

[Willbillys]

This was a vacuum switch that would complete a circuit and illuminate a low-pressure light when hydraulic level was low. The part broke off and I can’t find anything about it at all and any help is greatly appreciated. Maybe I can bypass it or get a different gauge?

 

[crane operator]

That's a old hydramac skid loader isn't it?

These guys are in the town I grew up in, and they were the largest hydramac dealer. I actually grew up running hydramac skid steers. I'd call them and they would know what would fit and spec's. Probably would ship one to you.

That's if you really want to put it in. I'd probably just plug the hole and check the hyd level. I think they probably did that so if you blew a hose, you didn't starve the pumps for oil and ruin the pumps.

Hackert sales and service (641) 594-3777

http://www.hackertsales.com/Pages/default.aspx

 

[Willbillys]

Thanks for the feedback! I actually spoke to a fellow at Hackert today and he was perplexed at what I was referring to. I’d probably have better luck sending them these photos.

The machine is a Hydra-Mac “Mitey Mac 8C” and Hackerts claims they have never heard of a Mitey Mac in the 8C size, just the Hydra Mac 8C.

 

[crane operator]

Are you sure its a vacuum gauge and not pressure? That when the engine is running it has hydraulic pressure there, and if you lost all fluid (from a hose blowing), or it stopped pumping oil (pump out) it would illuminate the light.

Its also possible that it is a plugged filter indicator, that if the filter is providing too much restriction, either from the oil being too cold, or the filter plugged, it would make a light come on.

The switch actually looks like a air pressure switch that is used on air brake system treadle valves. When the pressure is too low, the light or the buzzer comes on in the cab of the semi tractor. They get activated at different pressure's. That's what that switch looks like to me.

 

[kshansen]

Does it mention in the book what that switch is for?

I would half to agree with crane operator and think it is a sender to indicate a plugged filter.

Just for kicks try hooking a tester to the wire terminal and the other lead to the housing of the switch and see if it has continuity. Then poke something in the hole where the fitting broke off and push it in while watching the tester to see if it opens or closes the contacts. Heck it's broke already so it's not like you are going to damage any thing!

The biggest problem is those type of switches were made for all different applications and pressures or inches of vacuum (have seen them used to indicate high vacuum for plugged air filter warning) so without knowing what the rating on it was about the only thing would be if you could find someone with new old stock switch.

 

[Willbillys]

I’m not 100% sure, I had my mechanic look at the switch and he saw the ground was built into the switch so he gathered it stayed open under vacuum and grounded when pressure was lost. It had a single wire coming out of it and that wire was connected to what the manual calls a “indicator light”. The manual refers to the switch only as a “pressure switch.”

This is where the switch is located in the hydraulic system.

 

[crane operator]

You could set up a regulator on a air line to a blow nozzle, and adjust the pressure a few times to see what kind of a cut off the switch was on. 20-40-60-80 psi etc, until you got close to the range you needed to trip the switch.

The "mighty mac" was the name I think they put on some of the earlier really small skids that hydramac made, on later ones they sometimes still used the name, but the 8C model # is probably the number to go off of for parts.

 

[Willbillys]

I think I found a model number on it after lots of cleaning. I believe it reads “M-4001” then several spaces followed by “ 2 U 2”.

I’m still trying to take it apart. I put a hole in the center to see if the inside moves inward or outward but there’s something else behind the initial copper piece.

 

[crane operator]

It's probably just a diaphgram in there with a spring, holding a contact apart. The stiffer the spring, the higher the pressure needed to close / open the circuit.

 

[Willbillys]

found this online
http://www.parttarget.com/5930-00-2...10.html/-6B39332D-8915-49D8-8C97-C7DB8FF8E4AB

“Switch, Pressure

Mounting Method: Inlet connection
Overall Length: 2.000 inches nominal
Nonpile-up Contact Arrangement: 1 pole, single throw, normally closed, momentary action”

 

[Willbillys]

I’m seeing the part number listed with “4psi” beside it also.

 

[Willbillys]

Ok I’m going to order a low psi pressure switch. I measured this fitting at 3/8 and was confused as to why I can’t find any similar fitting but then I found a National Pipe Thread chart saying 3/8 diameter equals 1/8 npt which clarifies a lot! I can order a vacuum switch too just in case since they’re only 7 bucks.

 

[Hobbytime]

does that switch come apart? looks like the piece that broke off was just soldered on, you may be able to just resolder and use unless the internals were damaged..

 

[DIYDAVE]

That thread, on the fitting, in question looks like 1/4" npt. 1/8npt is like 27 tpi, quite a difference...

 

[Willbillys]

does that switch come apart? looks like the piece that broke off was just soldered on, you may be able to just resolder and use unless the internals were damaged..

The switch doesn’t come apart but I’ve alresdy damaged it enough for it to not be fixable. I believe it could be soldered, though, had I not attempted to take it apart.

That thread, on the fitting, in question looks like 1/4" npt. 1/8npt is like 27 tpi, quite a difference...

I’m confused by the NPT sizing at the moment. I measured the OD of the fitting to be 3/8 which seems to translate to 1/8 NPT, while the 1/4 NPT translates to .54 according to a couple charts I saw. I trust it’s 1/4, though, just confusing upon first research.

 

[xgiovannix12]

recently bought one on ebay for my backhoe

 

[Willbillys]

Maybe it is 1/8, looks like 8-9 threads at 1/4 inch, so possibly 27tpi at a full inch. I’m reading 1/4 has 18tpi.

 

[DIYDAVE]

Pictures can sometimes be deceptive. I'd use my stockpile of auction goodies to find a fitting that matches up, then use a thread pitch indicator gauge to find out for sure. Another way is to take the part to home cheapo, match up the threads, then look at the label, to see what you need...

 

[Willbillys]

Thanks everyone for the feedback that’s helped me narrow things down.

It’s a pressure switch, not vacuum, and the rating is 4psi “normally closed.”

I found a newer version of the same part for $87(!).

http://www.partdeal.com/stewart-war...si-normally-closed-single-terminal-78150.html

Maybe I can find a different one that does the same thing for less $$. At any rate, I’m happy to have found it. I am fabricating a small gauge/switch panel for the cab and just ordered an LED indicator light for this switch. Keeping the hydraulic pumps safe is a top priority.

 

[3X8]

Here's some on ebay

https://www.ebay.com/sch/i.html?_fr...ingle+Terminal+78150+Normally+Closed&_sacat=0