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cooldaddysquid's Avatar
 
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Electrical/fuse/AC question.

Hello all! I am happy to be the new owner of a 1984 911 Targa and am new to these forums. It's great to see so many people in one place that love these cars as much as I do.

I did my initial research on the best 911 for me, and now I am settling into learning about the car's specifics. I recently replaced the Radio in the car, and the following began to happen:

Occasionally, the AC blower fan will just stop. The only way I've been able to get it going again is to pull the first fuse (closest to the windshield) and reseat it. After this, the blower reengages and for the most part will stay on until the car is restarted a few times, but it will also sometimes stop in the middle of driving it.

In the interest of full disclosure, when I first replaced the radio, that first fuse (a 16 amp) popped a few times and had to be replaced. I re-examined the wiring near the radio and redid my work, and the fuse has stayed intact since. Also, the manual states that the first fuse should be a 25 Amp, but the one in place was (and still is) a 16 Amp fuse when I purchased it.

So my questions are:

1. Is the correct fuse for the first position (windows, etc) a 25 Amp or a 16 Amp?

2. Being technically inclined but having little knowledge of electricity and wiring, what is my next step with the fuse/AC issue (I have spare fuses, wiring, and a volt meter).

Thank you for your valuable feedback!
Old 05-25-2012, 04:48 AM
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Gary H 1978 911 SC
 
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My book covers 78-83 but the AC blower fuse is 25 amp and it goer to a relay real close to the blower motor. Tap the relay with a screw driver handle and check for power in and out of the relay.
Old 05-25-2012, 05:10 AM
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you have a bentley?

i have used mine many times in wiring work. I have completely replaced my front fuse panel with this and a wiring diamgram is really valuable when doing anything on these cars... It is a 25 amp on mine as well...

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83 SC Targa -- 3.2SS, GT2-108 Dougherty Cams, 9.5:1 JE Pistons, Supertec Studs, PMO ITB's, MS2 EFI, SSI's, Recurved Dizzy, MSD, Backdated Dansk Sport Stainless 2 in 1 out, Elephant Polybronze, Turbo Tie Rods, Bilstein HD's, Hollow 21-27 TBs, Optima Redtop 34R, Griffiths-ZIMS AC, Seine Shifter, Elephant Racing Oil Cooling.
Old 05-25-2012, 07:19 AM
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Carrera Fuses.

Quote:
Originally Posted by cooldaddysquid View Post
Hello all! I am happy to be the new owner of a 1984 911 Targa and am new to these forums. It's great to see so many people in one place that love these cars as much as I do.

I did my initial research on the best 911 for me, and now I am settling into learning about the car's specifics. I recently replaced the Radio in the car, and the following began to happen:

Occasionally, the AC blower fan will just stop. The only way I've been able to get it going again is to pull the first fuse (closest to the windshield) and reseat it. After this, the blower reengages and for the most part will stay on until the car is restarted a few times, but it will also sometimes stop in the middle of driving it.

In the interest of full disclosure, when I first replaced the radio, that first fuse (a 16 amp) popped a few times and had to be replaced. I re-examined the wiring near the radio and redid my work, and the fuse has stayed intact since. Also, the manual states that the first fuse should be a 25 Amp, but the one in place was (and still is) a 16 Amp fuse when I purchased it.

So my questions are:

1. Is the correct fuse for the first position (windows, etc) a 25 Amp or a 16 Amp?

2. Being technically inclined but having little knowledge of electricity and wiring, what is my next step with the fuse/AC issue (I have spare fuses, wiring, and a volt meter).

Thank you for your valuable feedback!
Here you go.



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Old 05-25-2012, 07:25 AM
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Hi cooldaddy - congratulations and welcome.

I think something is up here too.
What is mysterious to me is the relationship between the power window fuse and your AC blower intermittent power drop-out. My fuse box lid has a card listing the location as a 25A as well, but I think you have another problem and perhaps should holding up until you eliminate it before replacing the 16A with a 25A.
Does it happen a lot, or when/if you operate the windows?

I think your radio wiring technique was probably ok, but again there is this coincidence.
The only thing I can think of would be to consider (FIRST) REMOVING the battery ground cable so you can inspect and clean the fuse block one fuse at a time (light emery). You might consider cleaning the ground points in the trunk as well.

Sometimes this cleaning can help, but if it doesn't it will require some more investigating of course. The only reason I can think of the fuse blowing would be due to an intermittent short in the power wiring from this fuse up to the wiring of the 3 door switches or the 2 motors. The power window relay is not in this circuit. But neither is the blower. :-(

If it does help however, then try replacing the fuse with 25. Although you could try your luck and do this first, but if there is a fault, now you'll need 25A to see it.

I hope this helps a bit. Let us know your progress.
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Old 05-25-2012, 09:05 AM
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BTW here are some of the gnd points - I think you are looking at G104 and G116 - this is for '85 - '89 but might help.



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Old 05-25-2012, 09:13 AM
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Thank you for all of the great feedback, guys! I'll take your suggestions and run with them, for certain. I've also got the electrical pages from a shop manual.

Dan, I'm wondering what the relationship between the power window fuse and the blower fan is as well. I don't know enough about the fundamentals of electricity to know intuitively what is up, but I'm now taking a crash course. Interestingly enough, the windows go up and down whether the key is in the ignition. This would lead me to believe that there's a hot line from the battery to the windows and could explain why the 16 Amp power window fuse has blown a few times in the past, but it still doesn't explain is why reseating that fuse gets the fan going again.

What may explain it is that the previous owner put a bigger AC fan in the car and added some vents to help out with unbearable Texas summers. Still none of this was happening in the week before I switched out the stereo. Arg.

Thanks!
Old 05-25-2012, 09:35 AM
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Yeah, the window relay and switch power, while fused, is hot all of the time pretty much right off of the battery. I sorta don't like that feature. I understand the fundamentals, and I certainly have the training, but my experience with automotive wiring is low. And intermittent probs are just a pain. The 'short' paths would be after the fuse.

hopefully if you can look at the fuse lines, see if you verify the AC / blower wiring as being stock if the PO did some work as you suggest. Maybe make a table. I am hoping it sticks out from the rest, and check that guy out. But i feel like I am grasping after that.

Another 'theory' might be the momentary main power short might cause the AC relay to drop out / open and kill the blower.

Not sure if you or 84's have a sunroof- same power window fuse, and I doubt your are using the seat heaters. Maybe pull that fuse for a while and see if you still get the AC symptoms.
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Old 05-25-2012, 10:18 AM
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It's a Targa, so no sunroof, but I'll be pulling the blower fuse to see what's up.
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Old 05-25-2012, 10:49 AM
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UPDATE:

I looked at the AC blower fuse in the second position, and it was totally jacked. I went ahead an replaced it, and now the new fuse(s) melt. I've read the AC fuse melting thread and will clean up the fuse box with a wire brush. Will send updates.
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Old 05-30-2012, 07:20 AM
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On my old 73 I put a circuit breaker straight to the battery. This is for the heavy red wire. Takes all the load off the fuse box.
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Old 05-30-2012, 11:23 AM
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Alright. I think I've solved the problem. Again, this stems from a severe lack of knowledge on all things electrical, but presuming the following:

1. All wires at the top of the block provide power from the battery.
2. All wires at the bottom of the block provide the hot lead to the car's various components.

And noting the following troubleshooting steps:

1. The AC line running to the bottom of the fuse block had two wires twisted together. One is the AC blower. I am uncertain what the second one does. I untwisted them, and removed the headlight cleaner line at fuse position 3 and am using it for the second wire now. There is also a loose wire. I am unsure as to whether it's been like this since I bought the car, or if it became loose during this troubleshooting process. Nevertheless, there is no room on the block for it.

During this process, I noticed that the AC fuse had a power line in the top of it AND a brass coupler that lead to fuse position 3 (which in turn had another brass coupler that led to fuse position 4 which also had a power line in it.) That led me to believe that the AC was getting double power. So basically, the top of the fuse block looked like this (I can provide pictures if necessary):

*Fuse 1*Fuse 2___Fuse 3___*Fuse4 (Where * is a line from the battery and ___ is a brass coupler )

Once I removed the brass coupler from Fuse 2 to Fuse 3, everything stopped melting.

However! I'm now faced with 2 new problems:

1. The AC is not as cool. It's not blowing hot, but it sure isn't all that cool. Maybe it was my imagination. I mean, it IS summer in Texas, and I've got black leather interior. I'm willing to admit that this is on me.

2. The car runs hot. I was driving around residential streets, and the temperature gauge got up to the third tick mark (roughly 10 o'clock.). Again, this is Texas in the summertime, but the previous owner stated that the car didn't overheat. This has only happened once before, and it was in similar conditions, except I had melting fuses. This was back when the two wires were twisted together and in fuse position 2. My thinking at the time was that one line was a cooling fan, and the fuse trouble was the culprit. Now, I have no idea.

3. What's up with that loose wire? Is there any easy way to trace these lines?

Thoughts?

Thanks again for all of your valuable feedback!
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Old 07-07-2012, 11:50 AM
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Fuse Panel Installation

Quote:
Originally Posted by brads911sc View Post
you have a bentley?

i have used mine many times in wiring work. I have completely replaced my front fuse panel with this and a wiring diamgram is really valuable when doing anything on these cars... It is a 25 amp on mine as well...

Nice job installing the fuse panel. I believe that is one of the nicest jobs that I have seen of the install of one of my fuse panels! Great work.
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Old 07-07-2012, 05:39 PM
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UPDATE:

Yep. I definitely was running double power to the AC blower (feeling moronic). Nothing has melted since removing the brass coupler.
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Old 07-10-2012, 07:02 AM
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Old 07-10-2012, 07:02 AM
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