Help figuring out why my AC fuse popped/burnt on the hottest day of the year..

[Hotshot]

Last week my Indy topped up my R134. System really blows cold. Better than my Honda.

Over winter I replaced front blower w Griffth motor / fan / fuse combo.

Clean wires, fuse points. AC has been a champ lately. I keep it on 1 or 2 and it’s fine.

Had AC on all day for 2hrs. Working great. In a traffic jam with it on Full I decided to close off the pax vents to really increase the blowing on lil old me.. it’s 88F out and humid. In Toronto that’s a hot day.

Then as I cruise down the HWY all AC dies. Knowing my fuses I try and adjust power seats ( same fuse ) dead..

Get home, look at fuse, she’s nuked. Wires are fine but top all burnt.

Did me blocking off all vents? Smugglers well looked fine, no funky smells.. put in new fuse and works fine.. so what caused it and should I re wire or dedicate an ac only circuit?

[patkeefe]

Is the screw tight on the jumper bar? Looks like there has been an issue at the jumper bar prior to this.

[Hotshot]

Originally Posted by patkeefe

Is the screw tight on the jumper bar? Looks like there has been an issue at the jumper bar prior to this.

Can you explain further? Never though of this, and I have had issues with this fuse before.. I thought is was seat related.

[blucille]

My understanding is the Griffith blower motor draws more current than stock. My 83 has the full-ice as ice Griffith system and it works great but I had all kind of electrical challenges due to the state of my 200,000 mile harness and all the ‘improvements’ previous owners have made over the years.

Tempted to go to the classic retrofit fuse panel but for now I put a circuit breaker in place of that one fuse and have had no problems since (12 months, lots of ice cold miles)

[GH85Carrera]

I have had my Griffith's system on my 85 911 for 11 years, and never had an issue with that fuse. The AC in my car is used all summer. I virtually never roll down the windows. I either have the AC or the heater on.

It is hard to tell from the photo, but those look like the Chinesium plastic core fuses. Ditch all of them for some higher quality and likely more accurate rated ceramic core fuses. The plastic core ones tend to get soft when hot, and the pressure squeezes them and the contact becomes poor, and the resistance goes up. I threw all my plastic core fuses in the garbage long ago.

[Mike Andrew]

Had the same problem prior to adding Griff's front condenser motor. Turned out that somebody had done a repair of the wire to the fuse and had used smaller gauge wire. That led to high current draw, annealed fuse clips, loose fuse, arcing and fuse failure. I repaired the wire and added a blade type fuse holder in place of the original fuse and solved the issue.
You may want to have a look at the wires behind the fuse panel and make sure the fuse clips are holding the fuse snugly. It sure looks like you are pulling too much current based on the heat discoloration.
I have had no issues since my repair and adding the new fan motor from Griff. The old one had dead spots and would blow the smuggler's relay fuse.

[Hotshot]

Thx guys. The front fuse is perfect.

I think I’ll check out the wires. I have debated pulling the whole fuse panel and using the new blade type one our host sells.

Those are cheap fuses. I put a better one in.

[Hotshot]

Originally Posted by GH85Carrera

those look like the Chinesium plastic core fuses. Ditch all of them for some higher quality and likely more accurate rated ceramic core fuses. The plastic core ones tend to get soft when hot, and the pressure squeezes them and the contact becomes poor, and the resistance goes up. I threw all my plastic core fuses in the garbage long ago.

Yup. I bought a pack of them thinking newer, better.. lol.

[patkeefe]

If you look closely at the photo, you can see that the screw was tightened with he wrong size screwdriver, and it was tightened with a lot of torque, such that the screwdriver slipped and rounded off the screw. I e also appears that some ort of shim was placed in there, like a bit of wire.

If there is not a solid path for electrical contact, this is what happens...the connection gets a tiny bit loose, and conducts electricity in a non-optimal fashion. And when you get a high amperage going through it (such as when the AC system is loaded fully), a fried connection results.

If you fix the wiring issues, or install a separate fuse or breaker with a good wiring connection, you should not have any problems again. I don't think that simply changing your hardware, which works fine, will solve any problems without fixing the wiring issues.

[fred cook]

Does that fuse power both the front condenser fan and the main condenser fan in the smugglers box. If so, the answer may be to split the load, sending one of the power wires to a different fuse. I measured the power draw on my SC with both fans pulling from one fuse location and it measured right at 25 amps. Once I split the load it worked without any trauma.

[dhanl82]

I also moved one of the fans to another fuse on my 82SC for the same reason, works much better.

[pavegeno]

Griff's four condenser system for 12 years and no electrical issues. I only use fuses from Porsche.

[Jonny H]

You know what to do....

[David Inc.]

Maybe something started to short out in the controls? My wires melted down behind the a/c fan dial before blowing the fuse.

[Hotshot]

Originally Posted by Jonny H

You know what to do....

In due time! Friend wants one too

[Hotshot]

Originally Posted by David Inc.

Maybe something started to short out in the controls? My wires melted down behind the a/c fan dial before blowing the fuse.

My seats shorted out too and the blower was fine. I’m thinking that terminal is suspect.

[kuehl]

Griffiths has sold over 1882 of these motors since 2008. I can only recall 1 motor a customer complained about. We asked them to return the motor, we provided him a free replacement.
The motor he returned we tested for 3 months trying to get it to fail at various speeds, conditions and hours of running. It never failed. I gave it to another customer later that year for free and he he has never complained.

There are several issues with the factory circuit. Use of non tinned wire, many contact points and long runs (such as thermostat to compressor).

As Pat Keefe pointed out, the first place to start looking for issues is the fuse contacts and integrity of the wires in the terminal block. Next place is the primary AC fuse connector; you will find many 911's and 930's with melted plastic relay connectors running OEM blower motors. Next place is the factory fan speed control switch.

And, if you have electric seats a failing seat switch will toast the #2 25 amp fuse quickly; had to remove my driver's seat and replace my switch 2 summers ago, and we had an AC customer who thought our system was toasting his fuse too and it was his switch in the drivers seat.

Nick, feel free to return the motor to us and we will test it for you.

Johnny Boy, you know what you can do, keep playing the troll.
No respect my friend.

[Hotshot]

It was my fuse and vibration. I cleaned the contacts well and used a ceramic fuse. So far so good.. I re built my seat switches for that very reason.

[kuehl]

Awesome. Enjoy the 4th weekend.

Griff

[gsxrken]

34 year old wire harnesses and connections that were nowhere near mil-spec or marine grade to start with... gremlins are a growing part of this hobby. Glad you sorted it out so easily.

8 years with Griff’s 4 condensor system and zero blown fuses on my 930... carry on.