My AC went out the other day.

Looked underhood and Compressor was not engaged. Pressures checked good so I broke out the service manual and followed the TS tree with my meter.



So I checked the underhood No 56 20A fuse and it was BAD. I replaced the fuse, and when I started the AC up it blew again. Hmmm....so I just moved on to the next step.

So then I checked the Relay. GOOD

Next step is to check for Battery Voltage at the underhood relay 4P socket.
BAD.
No voltage present. I checked continuity (which I shouldnt get any) and I got a weird -.516. Sounds like a short inside the fuse box. To be sure, I also checked for continuity from fuse box to the compressor connector. And I got continuity.

According to tree, fuse box is bad. So I got one from the junkyard, installed it and everything checked good, started up AC and worked like a champ.

This was yesterday evening. It worked great all last night and again this morning on the way to work. But as I start my car up for lunch, it does it again. AC clutch wont engage AGAIN. Same exact symptom, clutch not engaging, burnt No 56 fuse. I replace fuse, fire up AC and it burns out again.

I'm about to go check battery voltage again at that 4P socket and ill report back. I guess it could be a fuse box again, but that would just be very odd unless it's a recurring theme with those things on our Civics (Its a 98 Hatch btw)

Just wanted to post back to see if anyone has any ideas or im just flat out missing something....

 

Hmmm....just occured to me, I cant recall if I replaced the fuse before I moved on to the next step....had I not done so, it would def fail at the next step huh?

Ill report back...

 

Yup.....I hadnt replaced the fuse and now im getting the battery voltage and the compressor clicks when I jumper it...It really helps to write it out....whole diff direction now....LOL

 

Fixed?

 

Nope still bad

OK....I just went through the entire Condensor fan and Compressor clutch not engaging TS tree. Everything checked good.

At the end of the Compressor TS tree, it says check connections from AC pressure switch and the ECM connector, if good swap in new ECM. Those 2 connectors are clean as a whistle. Ill clean em anyway as well as any other connection I can get my hands on and see what happens.

There's the AC system TS tree which pretty much starts off with me checking a connection on the AC thermostat (which is on the Evaporator right?) which would be a huge PITA to get to....I think Ill try cleaning some connections before I dive into that craziness

With the No 56 Condensor fan fuse blowing though (like 3 or 4 times....and when the car hasnt run for a while, the AC seems to work for a lil while until it blows again)....There's got to be a short somewhere right??

 

So fuse 56 is still blowing after replacing the hood fuse box? If so, that's the problem and I can help you pinpoint it.

 

Yes please

 

Nevermind...I'm pretty sure I found it

On the compressor, the small rubber connection that goes from clutch to the thermal protector appears to be a lil exposed and appears it has to opportunity to ground out.

Turned on my AC, clutch engaged, AC running. Used some long needle nose and grounded it against the compressor.

Clutch disengaged, fuse blown!

One question though, since its right near the compressor and engine where there's great deal of heat, what type of tape should I use to insulate it? Electrical tape will def melt off

 

Get a replacement thermal protector with harness from a junkyard or cut, splice, solder, and shrink wrap the one you have.

 

BUMP....

It's still blowing the fuse...I isolated the short to the compressor but it doesnt seem to be the wiring. When I wiggle the wires, it doesnt jump at all really. So its probably inside that rubber thing of the thermal protector. Ill go scoop one up from the junkyard.

I shouldnt have to evacuate my AC system to replace it correct?

 

The short is probably in the compressor field coil. Resistance test it.

 

Damn why didnt i read this before i went to the junkyard?! Lol

Well its 5.1 ohms at 200F (hot engine)....does resistance rise with heat?

And i got conitnuity on the other one

 

I could grab a field coil from the junkyard as well correct?

 

The field coil test? You need to do the resistance test with the engine cold.

What is "other one"?

 

Not yet. Too soon.

 

If you remove the compressor clutch relay from the hood fuse box, does this prevent fuse 56 from blowing when you turn on the A/C?

If you remove the condenser fan relay from the hood fuse box, does this prevent fuse 56 from blowing when you turn on the A/C?

 

Just got home....letting my engine cool atm....so let me be a lil more specific to my problem.

After I repaired that bare connector on the thermal protector, the AC worked fine for about a week or so, then the fuse blew again. The engine was still hot and I tired another one, it blew again. The next morning when the engine was cold, I tried another fuse and AC worked fine again. I went another few days or so, and it blew again.

I let the car cool again, and shot wires. Everything tested fine. Replaced fuse and car ran good for another day and a half until the fuse blew again (yesterday) I tested wires while the car was still hot, and when I tested for continuity from the compressor connector to ground, I got continuity (short somewhere from connector to inside the compressor). This morning, I thought maybe while the engine was cold, I might get some AC on the way to work. Nope nothing....

When I got to work, I got my short and tried wiggling wires to hopefully pinpoint the short. No change. So here I am now.

IIll try that relay test as well....good idea....Im letting my car cool so I can get an accurate resistance check.....Ill report back...thanks!

 

The continuity test thats before the resistance test. I wanted to test it while the engine was hot to see if that had anything to do with my problem

 

Definitely resistance test the coil when it cools. But note the very low Ohm reading for a good coil. Even when good, it will read continuity to body ground. Do the relay tests that I mentioned to see which removed relay prevents the fuse from blowing.

 

Hmmmm.....Oh I get why there should be continuity, cuz of the thermal protector....its actually in that hole against the body. Ok....So, "if" the field coil is causing the short, I should see a lower than normal resistance reading?

Anyways, I did the relay test....I dont have the car running (key = on), cuz im obviously waiting for it to cool but I have the AC running and the fuse isnt blowing now. I tried each relay individually and now have both relays in and fuse isnt blowing. This intermittent crap is killing me!

Car temp is at 113....Ill prob have to wait til tomm before it will cool completely....even then, its still 90ish here....it isnt gonna get much cooler....so isnt my resistance gonna be a lil higher than normal? I wonder how high? hard to guess i can imagine...

BTW.....about this morning....the car AC did kick on for about 60 secs before the fuse blew....Im thinking after the resistance check Ill have to wait til I can get my car running again to do the relay test....

 

The continuity tests for the coil and thermal protector are different.

In the diagram, you should measure continuity between the two connectors of the thermal protector. You should not measure continuity to body ground.

For the coil, you should measure continuity to body of compressor, as shown in the diagram. But a specific low resistance should be read.

 

OK....car cooled, Ohm'd out at 4.7....out of tolerance....looks like a bad field coil

It appears I got a Denso compressor though....and sounds like they're pretty hard to find...im guessing using a Sanden compressor field coil is probably wont work huh?

 

I assumed you had a Sanden. The specs are a little different for the Denso.

You may want to test again early in the morning when it may be cooler.

 

Hmmm...I don't see a thermal protector on the Denso compressor.

 

I know this won't help, but I've had my entire underhood fuse box torn down to its individual parts on my kitchen table (I dropped a very small metal piece down inside it and I was trying to find it before I "let the smoke out of my wiring"). Put all back together and in the car and haven't had a bit of trouble. I don't see how one could "go bad" unless there was a bunch of corrosion or something.

Interested to see what the culprit is though...