Help with A/C! Pulling my hair out!!

[Speedracer5767]

So I recently put P/S and A/C back on the CA in my S14. Everything works well at idle. Engine runs great and P/S is smooth. A/C is cold as hell as long as i'm idling. If i take off from a standstill the A/C fuse blows and I lose my wonderfully cold air. I have replaced all necessary components-Relays are good, FICD is good, and as far as I can tell all the grounds are good. Power and grounds all seem to be working well at idle. However I cant seem to find the info on the correct amperage for the A/C fuse. The stock S14 is a 7.5A. What is it supposed to be on a CA? I have searched for this and even went though the FSM and cant find a thing! Please HELP!

[float_6969]

Just stick a jumper wire in where the fuse goes and then see what melts/catches on fire when you take off. Then you'll where the problem is!

LOL, I'm J/K of course. This is a very odd problem. The closest thing I can relate to it was a similar problem I had with the A/C in my '92 civic. The A/C system would randomly blow the A/C fuse. It was more common when it was hot and had been running for a while, where as it rarely happened when it was cold. I continued to replace the fuse until it became common enough for me to be able to diagnose. What I discovered was the electromagnet in the clutch on the A/C compressor had some of the insulation get thin in the windings and would short to ground when it got hot. I replaced the electromagnet and it has been fine since.

If you could source a clamp style ammeter or multimeter, you should be able to measure the current draw on the individual components of the A/C system and find which is exceeding your fuse rating. IIRC the only parts of the A/C circuit that actually consume current are the FICD and the electromagnet in the clutch on the A/C compressor. Everything else is a pressure switch or temperature sensor of sorts. This doesn't mean they couldn't be the cause of the short, but they are much less likely.

[float_6969]

Something else just popped in my head. I'm leaning towards the FICD, as it only functions when the car is at idle. Once the throttle is depressed, the FICD valve is closed IIRC. Perhaps there is an internal short in the FICD causing the fuse to fail. You could also try increasing the fuse capacity to 10A and see if that fixes the problem. If that doesn't work, then you've got a short somewhere.

[Speedracer5767]

Thanks for the suggestions. From the time that i made the first post, to now, i have done some experimenting with the system. I narrowed down and out all of the relays and switches. The FICD is still on my mind though. I called the local parts store to find out what an 88 Pulsar wold have for the A/C clutch fuse and found out it takes a 20A! S14s have a 7.5A! So i tried a 20A and it still blew it! Next I put in a 25A as my last resort and it worked! However, my idle is not being raised any when i am at a standstill. So i think the FICD is F'ed, even though i replaced it already(with a used one). My original one was broken and had no continuity. The new(used) did, but it still could be bad. Overall though, I went on a 500mile roundtrip and as long as its not stop and go traffic, i can control my idle and the A/C blows cold as hell!!

[float_6969]

Glad you (sorta) got it figured out. I'd still get another FICD from the parts store if possible. I wouldn't think it would be THAT much. It might be something you have to get from Nissan though. Parts stores get weird about idle control valves.