Hard wiring a 12v air compressor (2 Viewers)

[Silveredition]

Gday guys, I do most of my 4x4ing on the beach, so spend a fair bit of time pumping the tyres back up... I have a perfectly good Thomas Blue Tongue compressor which has been going well for about 15 years - but it is SLOW! I decided to buy a cheap 12v compressor from the 4wd Supacentre - it is a twin piston beast with a supposed 300L/min and 90 amp power draw.... my 31x10.5 15 tyres take about 30 seconds / tyre to go from 18psi to 36....
I am currently fabricating a mounting bracket for the compressor to fit between the exhaust and gearbox (about the only place I can find to fit it out of the cab..).
I want to switch it on via an additional dash switch (a rear demister switch from the wreckers), but was wondering what the pin layout is on the switch for power-in, power-out, and the switch light. The compressor has a basic 1 wire in and 1 out on/off switch...
I have attached photos of the switch, and have numbered the terminals 1,2,3 for ease of any explanation...
Also, what amps can the factory rear demister handle (no- I am not going to put 90 amps through it!!! I have 3b&s for the power cables, a 120amp circuit breaker, and 175amp Anderson plugs...)

Thanks for any help - photos to come of the bracket, mounting position etc for those interested...

Drew

 

[g-man]

I assume blades 1 and 2 are "hot in" and "switch light". They can be powered with one wire but piggy back a smaller wire from the main feed to the "light post". the one on the bottom (3) sends hot to the compressor, once the switch is thrown.

Test the switch: Just hook it up to a jumper wire from the positive battery to one post 1 or 2. then put a test light on ground and post 3. If the test light comes on, you've got the wire on 1 or 2 hooked right to power the compressor. if the test light stays off but the switch light comes on then the wire you have hooked to 1 or 2 is powering the light.

 

[Silveredition]

Thanks g-man - I will have a play over the weekend!

 

[60Works]

Compressors like to be mounted away from heat and high enough to not get wet. At the very least, the inlet air source must be elevated.

 

[OSS]

Since you've got to switch the compressor on (90A!) via a relay anyway, the Toyota switch can handle the relay trigger without batting an eye. Relays typically only require mA to trigger. That switch can handle several amps. The bigger question is the gauge of wire to use from where the compressor will be mounted to the battery. That's going to have to be very thick and expensive cable.

 

[g-man]

OP references 3b&s = brown and sharpe ...aussy wire gauge standard. Basically equivalent to 3 AWG (american wire gauge). And mentions using a 120amp circuit breaker. so I think he is planning on using a relay or maybe the compressor has one built in? Also not sure what the 175amp anderson plugs are??

 

[NearJetties]

This thread will be helpful. It’s a different compressor but likely similar. Lots of great info on mounting options and wiring.

Puma 12V Compressor

 

[Silveredition]

Thanks guys, the compressor has twin 90amp relays from factory, and a 120psi pressure cut out. When it isn’t connected to a tyre it only runs for a second or 2 before building up 120psi in the hose and turning itself off - it is nice not having it running all the time!
Anderson plugs are just wire connectors to connect the 3b&s cable to the compressors wiring (after cutting off the original alligator clips) the Anderson plugs handle big amps, and are a secure, but removable connection.
I would have used the factory rear demister switch (as the rear demister screen doesn’t work anyway), but I was worried about frying something deep in the dash if I did anything silly wiring it up...
I will check out the link to the Puma compressor....
Below is the circuit board on the compressor - unfortunately I took a photo of the back...

 

[Silveredition]

Getting there with fabricating a cradle to mount the compressor between the gearbox and exhaust....

 

[OSS]

The front tires churn up tons of dust/dirt/ when driving on dirt trails. Any thing mounted under the truck is going to get hammered.
Also the rear driveshaft front slip yoke slings grease out (if it's lubricated like it should be) which will coat everything in its sling path. Take a look under the truck to see where that is. If the compressor is in its path, it'll get slimed.

The area/air all around the exhaust pipe is extremely hot when the engine is running and will most likely overheat a compressor that's needs cool air. Add to that the coating of dust/dirt/grime that will inevitably coat the whole thing & hamper cooling even more - and from the looks of it, under body mounting looks very challenging.

Anyway- just thoughts that came to mind.

 

[Silveredition]

Gday @OSS
Thanks for your thoughts / comments! I agree 100% with everything you have said.
I am not sure how long the compressor will last, or how effective it will be! It certainly is a lot of mucking around getting it mounted.... it will be fun while it lasts!!

 

[Silveredition]

FINALLY finished!! I had to move one of the mounts, and I worked out the wiring to get the additional rear demister switch to turn the compressor on. I ran air hose and Nitto fittings to the rear of the car. Now when I turn the compressor on it runs for about 3 seconds before turning off when the pressure in the hose reaches 120psi. I quite like that it only runs when pumping up a tyre and urns off between tyres. I also sealed the compressor with automotive sealant / adhesive, and encased the circuit board in the same stuff...
Now to see how long it lasts!!

 

[Silveredition]

So, I finally had the chance to use the compressor for what I really designed it for - a camping trip 1400km from home where I need to pump up the car and boat trailer tyres as quick as possible in 40 degree Celsius heat... after a hiccup on the first day (it doesn’t like getting to the 120psi cut-out), I made sure the air free-flowed through the hose the whole time so the compressor was continuously running... the usual time to inflate all tyres was cut down from 30 mins to 5!! All good - and we got a few good fish too!! Here are a couple of pics! Drew

 

[Silveredition]

Just a quick update - after almost 2 and a half years (used weekly each Summer) the compressor is still working perfectly! I am surprised - but it is only turned on when the car is stopped, so it isn’t running when the car is growing up dust / mud etc...
I did burst a hose, but had enough slack to shorten it...
I am loving the speed and convenience, but the car is currently getting an engine rebuild so it will be a few weeks (months??) before I get to use it again...

 

[JamesR]

Thanks for the post. I've been considering hard wiring a compressor and I have more to consider thanks to your write up and those who responded. A question regarding your quick release fitting near the rear bumper...do you have a cover for it to keep it clean so dust/dirt doesn't prevent a good connection?

 

[Randy88FJ62]

90 amps seems high for a relay to run it. At that point I'd just turn it on/off with a switchable circuit breaker in the engine bay and forgo the switch.

They run about $40 for a nice eaton one (they manufacture them for blue sea).

Eaton's Bussmann Series 187100F-03-1 Circuit Breaker | Waytek

Eaton's Bussmann Series 187100F-03-1 Marine Rated Surface Mount Circuit Breaker, 100A, 48V is in stock and ready to ship. Order today!

www.waytekwire.com

 

[Silveredition]

Thanks for the post. I've been considering hard wiring a compressor and I have more to consider thanks to your write up and those who responded. A question regarding your quick release fitting near the rear bumper...do you have a cover for it to keep it clean so dust/dirt doesn't prevent a good connection?

Gday mate, no I don’t have a cover, and I have never had an issue with fitting or releasing the hose...

 

[Silveredition]

90 amps seems high for a relay to run it. At that point I'd just turn it on/off with a switchable circuit breaker in the engine bay and forgo the switch.

They run about $40 for a nice eaton one (they manufacture them for blue sea).

Eaton's Bussmann Series 187100F-03-1 Circuit Breaker | Waytek

Eaton's Bussmann Series 187100F-03-1 Marine Rated Surface Mount Circuit Breaker, 100A, 48V is in stock and ready to ship. Order today!

www.waytekwire.com

The compressor has 2x90amp relays fitted as standard. I wanted to be able to switch it on and off with a dash switch instead of having to get under the bonnet, so an additional rear demister switch on the dash was wired into the compressors on/off switch, and works great. I do have a circuit breaker in the engine bay as well - don’t really want the car to burn down if a wire comes off under the car...

 

[Randy88FJ62]

Compressors mounted near exhaust of in the engine bay have shorter life expectancy due to heat. My friend worked at an offroad garage and all their arb compressor failures were people mounting them in the engine bay. Just a head up.

 

[Silveredition]

Compressors mounted near exhaust of in the engine bay have shorter life expectancy due to heat. My friend worked at an offroad garage and all their arb compressor failures were people mounting them in the engine bay. Just a head up.

Thanks mate. Where I have mounted mine - under the car behind the transfer case, I can hold my hand on the Compressor cradle next to the exhaust without getting too hot...