47-55.1 Bagged compressor wiring, why so hot?

[gigamanx]

Hey all, the rear bag kit is in, everything is wired and I am able to operate the system. This is an Accuair e-level setup with an Air Zenith compressor. The hot wire coming straight from the battery to the relay is getting very hot when the compressor is running. Is there something I'm missing on how wiring works?

Currently I have a 8awg from the battery to a 40amp fuse. 8awg to the relay. I did confirm the battery goes into the "30" pin on the relay and the compressor is on the "87" pin. There also seems to be a small wire going to the e-level controller that is attached to that 8AWG battery wire. It does not seem to get hot even though its on the same line.



The wire I'm holding is the one to the battery. Also the one getting so hot that smoke is coming from it after a little while of the compressor running. Almost like there is a major amount of resistance at that wire. The wire is not hot at all at the battery end, only at the relay end.

Relay is
87 --/ -- 30
86----85



Last image I have is the wiring diagram I think is correct? So looking at that the wiring seems to be all in the right place.



finally, I did start with a 70amp inline fuse and dialed it back to a 40 amp since I only have one compressor and thought maybe I'm allowing too much power through to the relay. It doesn't seem to have fixed the issue.

[joedoh]

when the 12v+ wire is getting hot, its almost always current draw.

a few words on fuses: fuses are a current limiting device, meaning a specific amount of current will flow through it and a specific overload will make it burn apart. you may think that this overload limit on a 40A fuse is 41A but its not. in fact, 90% of the time what burns a fuse is a direct short, its that instantaneous ramp up of current that causes the heat to pop the fuse. actually an automotive style fuse will pass a gradually increasing current to almost 2 times its rated limit before opening. a wafer style anl almost 3 times. a circuit breaker will pass more than that, if the increase is gradual enough, and some even self reset!

so a fuse is there to protect the current limit of the wire, not any devices attached to the wire. actually its the insulation that it is protecting, because if the insulation smokes off, more damage can be done by the hot wire shorting other components. more on that in a minute.

what is going on is that your AZ compressor starts by loafing, well within the limit of the fuse and wire, and as pressure increases so does the current load, gradually. as current load goes up so does heat, which increases current load. if this sounds like a runaway doomsday device, it is, in fact all electronic devices share this trait, higher current increases heat increases current increases heat so on and so on till boom. (look up why MOSFETs were developed, interesting)

so is your AZ going to draw more than 40A? absolutely. will the fuse pass more than 40A? also, absolutely. is your 8ga rated for more than 40A? well maybe slightly, it is I am assuming stranded wire and not solid, but its not going to pass 50A safely, and definitely not 60A.

so a system that can draw more than 40A should not be fused at 40A on wire that is just barely capable of 40A. you may not need more fuse, but you definitely need larger power wire. in my opinion AZ compressors are power hogs.

make sure all your connections are good, that the battery is fully charged, and that the compressor ground is the same size as the power wire, is as short as possible, and is grounded very well. a lot of guys ground to the bed sheetmetal, thats fine if you have ground straps on the bed still, but if not go to the frame, and only if you remembered the ground strap from the battery to the frame. make sure the fuse for the system is no more than 6 inches from the battery.

the insulation story: once a salesman at the audio shop I worked at got tired of a customer calling about a blown fuse on an amp we installed. he was just excited and bumping his tunes and popping fuses like he should. but he lept calling and asking how to fix it, and the salesman told him "I dont know, cram a penny in the fuseholder". he came in the next day with a smoked amp and a nice 8 gauge sized stripe burnt in his interior carpet. oops!

[mr48chev]

Joe pretty well nailed it in that you somehow have more load than the wire you have wants to handle.

Any time I see splices in the wire or tape or shrink tubing where it shouldn't be I get suspicious that it is hiding may be the problem. Besides looking tacy it most often is where a corrosion or high resistance problem pops up later.

As the gauge of wire there are calculators to help figure it out right like this one https://www.wirebarn.com/Wire-Calculator-_ep_41.html

This one might be a lot simpler to follow. https://mgispeedware.com/wire-size-chart/

[gigamanx]

Interesting info! I'm clearly a newbie when it comes to automotive wiring. If I look at the charts that were suggested, 8awg looks ok, but I didn't share a critical piece of the equation...

The run is about 15ft long! so I coiled it up under the cab instead of cutting it. I'm going to go and rewire all that. I'm also going to get a new connector and splice the wire to the controller correctly at the connector point and not half way along the wire.

Part of the reason I'm using that wiring is that I bought this kit from someone who supposedly had it installed on their vehicle. I assumed that its all connected right since it didn't burn his VW to the ground.

Will revisit the primary wire and get back to y'all.

p.s. Great info on the fuses. I wasn't actually sure what they did other than "protect" the circuit.

[1project2many]

The other item to note is that the "80A" relay appears to be a "regular" size relay with larger contacts and terminals. Many of the buses in our fleet come equipped with similarly rated relays for the A/C condenser fans and blowers. They do not successfully handle large loads for a long period of time. I believe the contact points inside the relay are barely large enough for the rated current and as pitting occurs over time the point resistance increases and the relay fails from heat. In our applications we would likely add a high current capable solenoid good for 100% duty cycle and use the 80A relay to control it.

https://www.amazon.com/Rodgers-124-9...15988098&psc=1

the salesman told him "I dont know, cram a penny in the fuseholder".

Ouch! We like to call those "million amp" fuses.

[gigamanx]

Problem solved this evening! I replaced the wiring to the battery with a fresh 8awg wire. No issues at all with heat. I then took apart the pigtail that had been smoking. Low and behold it was all crusty and green with corrosion. Guess I should not have trusted the previous owners choice of wires. Looks like a 10awg too.

[mr48chev]

That old "following behind" thing again. Which reminds me the cat and I need spend a day under the back of the flatbed rewiring the whole tail/stop/turn lights that roofers evidently cobbled together years ago. Cat doesn't help much but he is great with Moral support.

[1project2many]

Originally Posted by mr48chev

Cat doesn't help much but he is great with Moral support.

Cats do more work if you use the Mouse interface.