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ALANSD 06-14-2002 02:15 PM

wiring fix?
I know Peter is familiar with this topic, as we messed around with it at Mystic.
The wire to my rear air bag compressor was cut...who knows why, and the compressor seems to work fine when powered up.
I traced the wire from the fuse block, and found it had power at the block, but no power a foot or two away under the hood area, where it goes into the wire "snake" to the rear.
I ran a new wire from the cut spot to the compressor as the problem was between the fuse block and the snake, so I tapped power at the front, and all worked well, although I noticed when the compressor cut off (bags at charged level) the wire seemed to "stick" to the power source, the battery splitter terminal.
For now, I am leaving it where I can manually connect power every so often, until I can get it run all the way into the fuse block. The seat has to come out before I can get in there to do that.
Anyone see any potential problems? Seems like a decent fix to me, if temporary. By the way I have 12 gauge wire in this splice, but no fuse between the line and the compressor.

PeterH-Airstreamer 06-14-2002 03:41 PM

stick means heat. If you solder the end of the wire, you don't take a chance touching the source with just part of the wire. For safety you would be better off to put a 25 amp inline fuse right where you connect it to the isolator(?) terminals.

ALANSD 06-14-2002 04:58 PM

agreed- what do you think abut an inline fuse, and a switch there with a connector to the isolator, a loop type ...
I actually want to run to the fuse block, it's getting under the dash there that is a problem.
By the way- how often are your rear bags down, and how long does the compressor run? Mine ran I guess 3-4 minutes before cutting off.

FrankR 06-14-2002 06:09 PM

Compressor, air bags, and electric
Having owned a GMC front wheel drive RV for 12 years should qualify some info.
Just a little basic info. Never connect any load with out some protection, as a fuse. The new car fuses are called ato and many styles of fuse holders are available. Pick a holder so fuses are everywhere. My guess[swag] for a fuse size would be 30 amps. In an other life, with the GMC, I installed a mechanical air guage in sight of the drivers seat with a switch that controlled a relay at the compressor. Additionally, I fabricated a air tank from some 4 inch schedule 40 PVC pipe, about 24 inches long with glue on end caps. The bursting pressure for that size PVC is about 480 psi. This PVC can be threaded for a 1/4 pipe fitting. The line to the dash guage was 1/8 inch nylon. At the air bags, there was a small 3/8th ball valve and a shrader fitting to be able to add air from any source, as a gas station, etc..
Some guys, got and connected a small 120vac compressor that could be powered by a shore line or their inverter. GMC 12 volt compressors were usually located near the radiator.

PeterH-Airstreamer 06-14-2002 08:07 PM

Alan, for the quick fix, sure a switch and inline fuse wired to the isolator (coach battery side) would work. At night you can turn it off, or else everyone is going to fall out of bed.:)
3-4 minutes is a long time for the compressor to run, which means your bags were low.
There is a small inline check valve that should be installed in all air systems, since most compressors do leak internally.
I placed the check valve between the tank and the airbags, so my bags hardly ever go down, just the pressure in the tank does.
In case you are interested to know why I placed the check valve in that location:
The grey box by the compressor is the pressure regulator. When the pressure drops ~80 psi the diaphram closes points, which sends juice to the compressor. Once the pressure reaches ~100 psi, the points open and circuit is cut to the compressor. Sounds like a nice and easy automated system, except without the check valve the airbags also deflate to 80 psi. So until you reach the 'cut-in' psi of 80, you are actually running your bags to low and the compressor has to work harder to get everyone back up to 100psi.
I would never have figured the above out, if I would not have installed an inline pressure gauge.
Disclaimer: the above applies to my system, other system may have different leveling valves that may prevent back leaking of the airbags.

ALANSD 06-15-2002 01:02 PM

Ok, here's what I did ---- found a pair of "orphan" wires that wenbt thru the dash to near the isolator. I wired these to a switch on the dash that was labelled aux, and not in use.
I wired the hot lead from the isolator through a 25 amp inline fuse. The switch will now turn on the compressor for the air bags.
Now if i can get the light above the switch into the circuit I will have a green light on when the comp. is running. Hopefully this system will work for me.Thanks Frank and Peter for the advice....

FrankR 06-15-2002 03:22 PM

If I may
1 Attachment(s)
The wiring you have done is great............except, I would be very surprised if that switch is rated for the intended load. A load of 25 amps is huge... A little guide. A 1/10 of an amp can kill......10,000 volts will burn off an arm...... I would strongly urge you to use a nice bosche type 12 volt relay. They are cheap at most stereo shops and Radio Shack at less than $5. These relays will easily handle 40 amps. Don't shoot the messenger....

ALANSD 06-15-2002 05:11 PM

Thanks Frank- I bought the switch at radio Shack - rated for 25 amps. The compressor had a 20 amp fuse before I redid the wiring to 25 amps.
I also used the quick disconnect plug ins at the switch. I did blow a 25 amp fuse when I first tried to start the compresor...seems like enough air was in the bags, so it didn't come on. Then the fuse popped.
I believe I will have to get a gauge in-line to check the air level in the bags. I could splice it into the air line between the bag and the compressor(?)
Also I don't get a pressure reading on the bottom of the accumlation tank, which I guess is ok, but I would think it would maintain some pressure level.
If the valve is working to keep the level in the bags up, then the tank reading is not imprtant:(

ALANSD 06-19-2002 06:36 PM

-I ran a new 10 gauge wire all the way thru to the back. Snaked it pretty thru the wiring looms all the way, tied it with wraps. Looks good.
Connected the new wire to the "grey" box with the compressor. Bam - fuse blew!! Tried another fuse, checked connections, compressor clicked, fuse blew. Seems like a bad compressor? If anyone knows...the grey box has a two screw in connectors, one marked line, one marked load. Seems like line should be where the hot lead attaches, as the compressor is attached to load. Right now I am the one who needs to get loaded.

where do you get the inline check valve? If I get one and an inline pressure gauge ahead of it...toward the bags, can i manually add air to the system and read the pressure?

FrankR 06-20-2002 07:40 AM

Compressor wiring
Greetings Alan,
I believe the grey box you are refering to, is the pressure switch. This device controls the compressor as to the on and off cycle. You are a little too far away for me to see how the makers wired the components of the air system. Ordinarily the [grey box] pressure switch has just 2 connections, as power in power out to compressor. I have seen in my past, where the makers, used the switch for the ground sideof the compressor. A 30 amp fuse is very strong .. And now, I think you should use a test lite or meter and discover the polarity of the wires. Go to the compresssor and disconnect the wires, remove from RV. Connect wires to a battery for a test to be assured the motor operates OK. For a quick test, a fuse is not necessary. I'm guessing but, it may be the compressor motor is wired with power direct and the ground is controlled thru pressure switch Check any reference manual to note wiring method. Please advice of any discovery.....Frank

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