Wiring question... No power to PS

Okay, quick question guys!

All my wiring is GOOD. I don’t have any bad connections that I know of…

My dual pressure switch ignition wire is causing me problems. It’s a 14-16 gauge wire with 20’ of length. It goes from the batter > toggle switch > down frame rail to pressure switch in bed. The PS is getting power… I checked the middle of the ignition wire and my meter shows power.

Here is what’s happening. I only got my PS to turn on once… The way I was able to do it was simple… I found a splice in the middle of my wiring and took a 12v car battery charger and just boosted the voltage on the wire and the compressors kicked on… I took the battery charger off it and they stayed on…

My question to you guys is… Is my ignition wire too small given the length I’m using on my vehicle? I know my fuses and wiring isn’t bad… I don’t think the PS is bad?.. What else could it be?

All this wire does is trip the coil in the relay. The amperage is minimal. I wouldn’t hesitate to use 30’ of 18 gauge.

So I would think pressure switch or relay.
You can easily test the PS by running your tank low and then make sure there’s power on both terminals. Or make sure there is continuity between the 2 terminals.

Voltage shouldn’t affect the PS so I say the relay is suspect. But I don’t know if they slowly die or just quit.

Have to remember the wire has to be rated for the compressor to run off of the pressure control. I had a similar problem. It was the ground for the compressor. Dodges are Notorious for electrical ground problems! You have half the problem solved. You stated you have power to one side of pressure control. Now that is one verified the voltage is present. Now could be intermittent. Go right down the line, see if power is present on both sides of switch when activated. Then travel back down to pressure control. If there on one leg. test on the other. if voltage is not present then bad control. You could also take off lead and ohm out coil. Heres what happened on my on my dodge I had a bad compressor ground and when I laid on the horn the solenoid stuck open. And I had to shut off compressor inline switch. Then if I turned on switch the horn would start to blow again. LMAO! It was a bad ground wire to my compressor. Fixed that and haven’t had a problem since. But also stated don’t rule out a relay also. verify voltages there too.

Good Luck,


I’m not sure it’s the ground… ALL My grounded wires are on the same bolt… And they all work.

The bolt goes right through the frame too.

I guess I can try moving it if I had to.

I’ll go outside and check the voltage again…

So you are you using a separate pressure switch and a separate relay, correct? If so, make sure your connections to the relay are correct. Maybe the wiring got switched up?

I fixed it…

I have the dual relay pressure switch.



To test my theory of not having a big enough gauge wire to the PS. I took 15’ of 10 ga and attached it to my PS. I then took my battery terminal 12v charger and hooked up the end of it to the 10 gauge wire… It works :).

So, it looks like I’ll just run the rest of my 10 gauge to the engine bay and leave it at that…

Okay, problem not solved… I think from the middle of my truck to the battery there is a problem with the wire… I found this out by leaving the good wire that was from the ignition wire (coming from truckbox to the middle of the frame). That wire works… I switched it with my 12v solenoid and hoped that the valve would work on the low current… It did not…

What stumps me the most is that the wire coming from the battery (which goes through a toggle switch + it’s connected to the ignition) it HAS power… I took a battery tester and tried it… So, I’m not sure what to think now…

What I’m just going to do is rip the 16 gauge old ignition wire COMING from the battery to the middle of the frame out. That’s the only section I know that could have the problem… but like I said, it HAS power… So, I’m not sure if I’m missing anything.