AC Relay wiring K5

[Chris Ziemer]

The orange wire on my AC relay (not resistor) is shorting my fuse out. This is a new development. The orange wire on the relay powers that relay and the high-speed fan does not work without it. I recently put a new five wire plug on for the relay and that is when my trouble started.
Common sense would say the relay plug that I installed has a bad connection, but I’ve tested every wire and connection and can’t find any problems besides the 12v orange wire.
This wire goes into the firewall, looks like into a plug. Anybody know where this wire ends? Why would decide to short out?
The rest of the fan speech work, only the high-speed fan does not work (due to the short).
The one picture shows the blade where the orange wire should go. The other picture shows the problem Chil orange wire.

 

[Wes Harden]

orange is from the blower switch it signals the high blower relay to close. If you pop the fuse with hi blower selected the relay may have an internal short, or you blower may be drawing to many amps

 

[Chris Ziemer]

Thanks Wes, that helps. I did unplug the fan, then turned on the high switch and it still blew. So the fan was out of the picture. I guess it could be a relay. I’ve went through a few of them, in trying to figure this out. At first, I thought maybe I blew a relay because that plug is a real pain in the butt to get into the relay. Really have to finagle it in there. Thought maybe I shorted something out while messing with that.
I pulled the fan selector switch unit out and there’s nothing unusual there. The funny thing is this all worked totally fine until I changed the plug and the relay. Since then, I’ve changed the relay again. Again I’m sure the plug is solid. I guess I’ll try another relay. Maybe they short out easily? I’m not sure.

 

[Wes Harden]

Double check your your wire placement in the relay plug. Also there were at least to styles of relay they might be wired different.
Ohm check that orange wire to ground switch off and see if it is shorted to ground

 

[Blue85]

I recently put a new five wire plug on for the relay and that is when my trouble started.

It's a shame you've cut up the HVAC harness and put crimp connectors in. That's just trouble coming down the line. Plus, you've put a smaller wire on for the red, which will put more heat into the relay and may cause it to fail, especially if the crimp isn't done right. But I suppose you see this kind of vandalism all the time.

Where did you get that relay? It's possible the coil has an internal diode for suppression. It's very easy to check with a DMM, but if that's your issue, the solution is as simple as swapping the black and orange at the relay. Those two terminals are for the relay coil and should not be drawing much current unless a) there's a diode facing the other direction or b) the relay is defective and has an internal short.

 

[Chris Ziemer]

Thanks for your post Blue85! It is a shame, my original wire harness had melted part of the plug where the red power wire was. So it didn’t really fit into the relay anymore.
I shortened up the power wire and fan wires between the connections as much as I could, hoping to avoid another meltdown.
It’s a great point you brought up, about different relays being used. I do see there’s a 15 amp and a 30 amp. The ones I have bought so far, literally do not tell me which they are. But I suspect they’re 15 amp. I did switch the orange and ground wires, but it’s still shorted out. It does not short out, when not connected to the relay. At this point, I think I’m running out of ability to figure this problem out. It could just be that I’m getting 15 amp relays, when it needs a 30 amp relay. Maybe that’s why it blows immediately… Though it did work for a little while initially. Will probably have to give it to the mechanic to do some testing.
I’ll let you guys know when I figure it out. For now, for this to have happened so randomly, seems like a mystery.
Supposed to be 114 here next week, so fingers crossed!

 

[Wes Harden]

Where are these relays coming from ? I had an issue 2 years ago with a new relay, trying to remember exactly what it was. I ended up getting one from Napa and it worked is still in truck. Also my plug was melted I was able to get 2 new ones. The terminals are Packard type 56 female, there are 2 sizes so double check before you buy.

 

[Chris Ziemer]

I bought two relays from Amazon, which were AC Delco. Surprisingly neither one of those have the amperage listed on the site or the package. I bought another relay, the initial relay, from AutoZone. Just some rando Brand. I actually just ordered an actual 30 amp relay from Summit.
If I’m not already, soon I’ll be relay rich!

So, the fuse blows when the orange wire is connected to the relay, even if the relay is not connected to the fan, i.e., the fan is not plugged in with the purple wire. So just passing through the relay, the fuse blows without any real load being applied to it. The only thing that’s happening at that point, is the resistor is telling the relay to take over. And of course, the orange wire isn’t even connected to the resistor.
In my mind, it must be a short somewhere though damned if I can find one.
Or, again, perhaps I’ve been buying the wrong relay all this time and the 30 amp will solve the dilemma.

 

[Chris Ziemer]

And Roger that on the terminals. The plastic housing around my power wire was actually melted, and wouldn’t slide into the relay anymore. Currently, I did pull out all of the terminals to the new plug and just put them in separately. I may just keep it that way and replace the red and purple terminals to accommodate the larger wire size. But thank you for that information, that will help me when I’m looking for terminals.

 

[BoondocK5]

You need to find that short. My pretty reliable way to locate shorts is run your volt meter (on Ohms) one to a known good ground, measure from where the orange red wire plugs in. Note Ohm reading, start unplugging things until you locate the culprit.(way easier said than done, I know)

 

[Blue85]

It sounds unusual, but it's possible the relay has a different pinout, so you're connecting orange and black across the NC contacts. Easy enough to check with a DMM. It's also possible you're just making the connections wrong? Orange and black would be on the two vertical terminals, with red/blue/purple on the three horizontal ones. It would be really weird for 3 relays in a row to have shorted coils and even a short to the case wouldn't matter since it mounts on plastic.

 

[Chris Ziemer]

Thought I’d give an update on my weird AC short. If you recall, I put a new pigtail on the AC relay and from that point on, no matter what I did, it would blow a fuse on the high fan setting.
Took it to a different mechanic and they realized the plastic terminal on the compressor was melted. I knew it had been, but it always worked before.
Well….after replacing the relay, there must have been more voltage to the compressor and it was too much for the melted compressor plug, thereby shorting out.
It was a dumb problem to have and not fix since I’d replaced everything else. Wish I could say I learned from it.
Thanks for everyone who helped with this issue.