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Discussion Starter #1
Okay, since I installed my new radio my heater/AC circuit is blowing fuses. I suspect I pinched a wire somewhere, but I really don't want to tear the thing too far apart. I'll bet I can hook up the old multi-meter to both sides of the fuse holder and watch it jump up (or down?) as I move things around under there to get an idea of where my problem is, but the question is, what do I set the thing on? I don't think I'm checking for ohms (whatever they are).

Who wants to offer up some guidance?

advTHANKSance
 

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Where did you tie in the switched power for your new radio? Off the original radio yellow lead? There is another yellow lead on the heater circuit but outside of that the 2 circuits have nothing in common. Yours in an A/C car if I recall. If you pull the connectors off both the resistor and relay under the hood you can eliminate those items. Didn't you have a problem with the heater lever switches shorting out to the frame? That problem back again?
 

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Discussion Starter #3
Not the switches in the dash, 'cause I pulled the top off and unplugged them and tried it, same results. I got power for the new radio from the fuse block, both switched and BAT (it has a clock and station presets). I think I managed to grind something up under the dash and it's just shorting out. I thought maybe if I could hook something simple up then I could just puch and pull a bit on the various wires and maybe get a hit...
 

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Doesn't the power line for the option A/C harness just plug into the fuseblock. Maybe a brown wire? What happens when you remove that?
 

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Hey Cecil, That Sprint looks so good with that new paint.
It's real easy to find that short you have. It is a brown wire, about a 14 ga. (a little thicker than most of the underdash wiring) and it goes from the fuse block (as John stated) to the heater/A/C controls. It remains hot even when the connectors are removed from the Heat/A/C switches (if the ignition switch is on). Yours is shorted to ground somewhere in between.
Here's a cool way to find a short:
Get a little 12 volt buzzer. Hook up the two wires of the buzzer to the two terminals that hold the fuse that's blowing. You can use a blown fuse and wrap the wires around each end and then snap it in the fuse socket. For your case you have to have the ignition 'ON' (engine off).
The buzzer will buzz as long as there's a short. You can then poke, pull, push, kick, etc., until the buzzer stops or is interrupted.
The best thing about using a buzzer instead of a test light is that you don't have to be looking at it to find a short like you would with a test light or ohmeter.

Just routine stuff from the dealership days.

Good luck,
Louie
 

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Just an idea for a buzzer, I made one from the seat belt buzzer from my 78 Camaro. As stated, Ray Charles could find a problem with one of these.

Jeff

P.S. My apologies to any blind people reading this....
 

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Cecil, I think you do want to check resistance to ground using an ohm meter. Some meters have a audible feature also. Anyway, put one test lead on the heater/AC circuit and the other probe to a known good ground (i.e. frame) then move around some wires and look for continuity (~0 ohms). I had a hard time finding a short recently and found it on the rear switch of the AC controller. It was shorting out to the support bracket. Check there if you have AC.
 

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All great suggestions. Just one thought and the reason I asked if it still popped with the A/C option harness unplugged from the fuseblock.
The original non-A/C wiring is still there. The connector that went to the internal blower resistors is still up there. Possibility that connector is laying against something. If you check the non-A/C schematic I believe that circuit also runs the back-up light switch and the turn signals. Possibility that the short is on these other items and not on the heater circuit. Unplugging things helps if you remember all the things on that circuit.
 

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Discussion Starter #9
Hey Louie, how are things? Thanks for the kind words. My paint is from One Day Auto Painting, although it took them longer than one day (they painted it thr wrong color the first time!). Did you get that steering column installed yet? I haven't put on the dual-plane intake yet...

I've seen this brown wire up in there, and I remember having trouble with it before. I'll look for it. Thanks for the buzzer idea. I'll get Wes (my 12-year-old) on that, it's right up his alley.

John, I think I have the extra connectors tied up out of the way, but I'll look for them also. The old heater connector is there, but I don't think it's hot with the A/C add-on harness, is it? The existing radio connector is my most-likely suspect of anything dangling loose.

Thanks for the ideas!
 

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The existing wires are still up there. The buzzer idea is great but it can also fool you if you don't watch. If there are items such as light bulbs tied to the line the buzzer will buzz. Check your non-A/C schematic to see what is tied to that fuse. Sometimes it's easier to unplug things before you try and use it.
 

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Discussion Starter #11
I have a fan again! Louie had it, I suspect you others did also. I managed to ground the brown wire when I grounded the new stereo (I was only upside down and backwards while doing this).

No more blown fuses. Now on the the next project...

Thanks all!
 
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