2000 Pontiac Montana solinoid clicking, what's it called?/

Your right it does have a plastic line with a needle valve type port with a light blue cap, and a tag that says --evap service port--, whats it for, what problems can it cause? Thanks for quick reply.

I have a problem with compressor ac clutch fuse blowing, even with clutch wires disconnected, not all the time, it will go 2-3 days without, then it will blow them instantly, until I wait a day and try again. And the abs light-service traction control, message display. It comes and goes, but if I turn the key to run position and wait three seconds before starting the engine, then abs light-sevice traction control message, do not come up, and all is fine. Whats the best way to check wheel speed sensors with a voltmeter? I have read if you turn hub 1 revolution/second, it should put out at least 1Mv. Also all lights flicker at night very discretely, and seems to be in semi-close sync with clicking from solinoid. I have checked wires/grounds, alternator and new battery, and im out of ideas. I know I should go get the codes read, but if I can troubleshoot with voltmeter, and a low 17Mv test light (computer safe) I would prefer to learn how to fix myself and learn something, than pay out and learn nothing. I know this seems like a lot of problems and I understand if its too much to try to figure out over the internet, but I do appreciate any ideas or advice you can give.

Your point is well stated. I wish gm would just incorperate the the ability access and retreive codes codes into each vehicle. The cost per vehicle to do this would be almost nothing, because they already have the codes stored in the vehicle, all it would be is a way to display them. Except they would loose millions in the $89-$159 in the service of retreiving the codes for us. Thanks for the wire info, I'll check it out. If theres anything else you can think of let me know.

I pulled the a/c clutch relay out, which takes the a/c clutch, a/c diode and the pcm out of the equation. I also have a diagram from mitchell and its money well spent. Can I conclude that the problem is in the wiring junction box(underhood). I did try swapping out the a/c clutch relay with the ignition relay with no change(still blew). Can a problem come from (upstream)the line side of the fuse? Thanks for your input

It finally started blowing fuses again and I do only have one ground. I even put a new fuse in, and for the 3-4 seconds it took for it to blow, it still was not to ground. I want to let you know that I am not even running the a/c this time of year but it is still blowing fuses. As long as the key is on, when it is in the blowing mood, it will blow, usually within 8-10 seconds. I did take the ignition main relay out, and it did not blow, reinstalled and it did blow. And like I said, with the a/c relay out it still blows. There is nothing but circuitry(no components just connections within the junction box) between the 10amp a/c fuse and the a/c relay connections. Is it in the connections of the junction box between the fuse and a/c relay or am I missing something else to check before drawing this conclusion?

It was blowing fuses, so I removed the ign-1, inj, elek, and tcc fuses. Put in a new 10 amp a/c fuse and proceeded to reinstall the removed fuses. At no point did any of the reinstalled fuses cause tha a/c fuse to blow BUT, when I installed the ign-1 uh fuse there was an obvious low pitch squeal(like an electrical drain)from around the a/c clutch. It seems like the a/c clutch circuit doesn't like the drain from the ign-1 uh circuit(the ign-1 uh circuit has the 'evaporative emissions canister purge solinoid valve'((eecpsv))that is continuosly clicking away and was the original subject of this thread. Also has 2 heated oxy sensors and the air injection sl valve and mass airflow sensor). Do you think I should replace the eecpsv or find out why it is clicking away randomly? Or do you have any other suggestions?

The clicking is not from the evap solinoid but from the throttle position sensor, which is not at all on the same circuit, so Im ruling out this as an a/c problem. But what kind of problems would a bad tps cause?
At no point did it stop blowing the a/c clutch fuse, when the ing-1, tcc, inj, or elek fuses were out. So I think its safe to say the problem is not from the feed side of the circuit. And if the fuse still blows with the a/c relay pulled out, the problem must be in the junction box or possibly with a ground connection or cut insolation. I have removed and cleaned every ground and cleaned connections with no resolve.
Even on the manual and auto a/c circuit diagrams, it shows nothing else in the ciircuit that can cause this problem. Am I wrong or am I overlooking somethig?
Thanks for your expertise.

Can you give me a little more detail on checking power and triggers on relays? Do I take the cover off the relay to test and inspect internally while installed in the junction box, or just check continuity across the pin connections with relay removed? What do you mean by 'power center', where are you talking about, in the tps or the relay, or the junction box? Thanks! Also I noticed that only the right side cooling fan is coming on when high engine coolant temp calls for fan/s. Is this normal or are both fans suppost to come on? Could this be blowing the a/c clutch fuse?