1991 Chrysler Fifth Avenue wiring/fuse problem. Help!

Tiny
JHUTCHISON40
  • MEMBER
  • 1991 CHRYSLER 5TH AVENUE
  • 3.3L
  • V6
  • FWD
  • AUTOMATIC
  • 175,000 MILES
Every time I would turn the A/C or heat on in my new yorker it blows a fuse. My dad had been trying to track the problem for five years now but he finally put a circuit breaker underneath my steering column. That stops it for a bit but if that circuit breaker gets too hot it shuts the blower off then I can't even open the windows. And then my airbag indicator light and parking break light wool come on. It also does it if I go up a steep hill.
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Thursday, December 12th, 2013 AT 12:34 PM

4 Replies

Tiny
CARADIODOC
  • EXPERT
It does what if you go up a hill?

A simple trick to finding a short is to replace the blown fuse with a pair of spade terminals, then use small jumper wires to connect them to a 12 volt light bulb. A brake light bulb works well. When the circuit is live and the short is present, the bulb will be full brightness and hot so be sure it's not laying on the carpet or against a plastic door panel. Now you can unplug electrical connectors and move things around to see what makes the short go away. When it does, the bulb will get dim or go out.

In this case, since it's a relatively high-current circuit, you may need to use a head light bulb. A brake light will only allow about one amp of current to flow through the circuit. A 9004 or similar head lamp bulb will let at least five amps flow. That will be enough to make the fan motor run, even though it will be at a reduced speed.

That circuit breaker is in the wrong part of the circuit to be of any help in diagnosing the cause of the problem because it is protecting too much stuff. That COULD be a clue, however. There could be broken and frayed wires between the front door hinges that are touching intermittently. If there are, you'll see the test bulb flicker in brightness when you open and close the door.

Do you have automatic temperature control?
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Thursday, December 12th, 2013 AT 1:48 PM
Tiny
JHUTCHISON40
  • MEMBER
The A/C or heat will turn off. The circuit breaker is the only thing keeping me from having to buy a $6 fuse every time I move that switch. And it doesn't have temp control. I'm taking a screen shot of what you said so I can tell my dad. Since he's the mechanic.
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Thursday, December 12th, 2013 AT 2:10 PM
Tiny
CARADIODOC
  • EXPERT
Just so I'm clear, the fan stops running. By "heat will turn off", I assume you don't mean the air gets cold or it switches to defrost mode. Switching to defrost when going up a steep hill is very common and has an easy fix.

Since the Air Bag light turns on when the circuit breaker trips, you have another indicator to look at besides the fan. Also, since you have the standard, more reliable, manual heater controls, there isn't likely to be a problem with that system that doesn't take out the resistor assembly. That unit has a built-in thermal fuse that would have blown by now if the fan motor was shorted or dragging. For that reason, I'm leaning more toward shorted wires between the door hinges. Do my light bulb trick but unplug that blower resistor. It's on the top of the firewall, under the hood, on the passenger side.

I bought a '93 Dynasty which is basically the same car, and I ordered it with every option available, except automatic temperature control. I'm smart enough to know how to shove a temperature lever around, and there's very little that can go wrong with that system.
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Thursday, December 12th, 2013 AT 5:41 PM
Tiny
JHUTCHISON40
  • MEMBER
Yes, when I go up a hill the heat/air will completely shut down and not blow air out. Also when that happens the windows won't roll down. I replaced the ignition switch last night since that decided to give up. We noticed that the wires in the harness connecting into the switch were completely bare and kept falling out. Can I go ahead and put the original wires back into the harness and see what happens? I know it will normally blow the 50A fuse. All in all, this car has been giving me heck since I got it. But I will definitely try the light bulb idea and I'll tell you the results.
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Monday, April 7th, 2014 AT 3:19 PM

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