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1955 Roadmaster


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So interesting problem.  My electric windows have a very interesting problem.  When the car has been running and heats up, the electric windows quit working.   I suspect the wiring harness has a short but I have no idea where it would get hot enough to short out.  Anyone have any suggestions where to start? 

 

Thanks. 

 

Michael 

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Is it all windows? I would find the electrical diagram for the car and follow that to give you an idea of where to start looking. A continuity tester can be used to determine which part of the circuit is failing. Once you know which part of the circuit is the problem then you will need to find out why. It could be a short or loose connector or something else that is affected by heat.

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Well, thats a pretty general description on cold, hot, any mods, and few observables so heres some ideas.  Thermally related electrical issues can be tough to pinpoint.

 

Am assuming that engine has a generator and points (analog) regulator on it, and if memory serves power windows and power seats run off the same relay and circuit breaker, and thats a thermal breaker and resets itself when the fault is gone.  Maybe someone can check me on that.

 

If the switch or relay aren't stuck on causing a motor "stall" condition to trip the breaker, as suggested above, another possibility is a poor (high resistance due to corrosion over time) connection someplace such that a high current load will have just enough power "source" to appear to work at cold (when charging system is putting out the highest voltage to the battery - have seen well over 15V on mine) and then as the regulator compensates for hotter conditions and lowers the voltage the high resistance of that poor connection robs power that would normally drive a high current load, like a motor, to work.

 

The places on my car notorious for that are where there is that flat blade/socket connection in the wiring harness - they are encased in this brittle clear plastic connector that sometimes shatters when you mess with it to make it more better.  So my thoughts are:

 

1) Visual the current gauge - does it behave any different at hot or cold when the windows are operating?  If a relay or switch is stuck, the expectation is it would stay discharging after you let go of the switch until the breaker opened.  The gauge behavior would also give you a clue as to if there was a hard short pulling more current at hot (it would show more discharge), or just a lousy connection (maybe not much of a drop at all).  Although if temp related it would seem to be the relay under the hood being stuck or high resistance across the contact points when closed vs the switch in the door would be more suspect.

 

2) If you have a schematic, visual all the mechanical connections you can see or find easily before tearing the door apart - any of the connection points discussed above, the wiring to the breaker, perhaps the impedance across the relay, clean up all the connections.
 

3) Does your car have power seats?  If they run through the same circuit (too lazy to get my book), and the seats behave the same, then it suggests a common failure upstream of the seats/window controls and motors.

 

4) After that next step would probably be to pull off the door panel and get a volt/current multimeter on the switches and the motors to see what is going on.  Just thought to give you some things to try before pulling interior panels off

 

 

Good luck let us know how it goes

 

 

Edited by KAD36 (see edit history)
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Wiring shorts are not heat/cold dependent, but wiring connectors might be marginally-connective during certain temperature events.  "Chafed wiring", where the insulator has been rubbed away over time due to the wire vibrating against a metal part, might be operative, too.  Bulkhead connector terminals are usually "out of sight, out of mind", but CAN cause some electrical issues as their terminals can corrode over time. 

 

Start at the generator and work outward from there.  Just need a simple test light to check continuity of the circuit(s) involved, but knowing how many volts "where" can be good too.  Take your time when you can devote a few hours to this quest, in an unhurried manner.  Being methodical, efficient, and focused can be good orientations in diagnosing things of this nature.  Of course, a good OEM Buick electrical schematic (Hometown Buick?) can be good to have!

 

Please keep us posted,

NTX5467

Edited by NTX5467 (see edit history)
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I just had a problem on a 53 RM power windows that worked one day and not the next. In my case, key on then depress the switch. You could hear the circuit breaker trip and the amp gauge drop just before it tripped. Yes it is hydraulic windows but some of the troubleshooting will be the same. I started with the wiring diagram; it looks like the breaker is in the glove box area on a 53. I never did locate it. I glanced at hometown Buick and it looks like the 55RM is located in a similar location. My short to ground was at the relay for the hydraulic pump. The previous owner installed the trip wire too close to the motor body edge and it rubbed through  

 

Everyone is spot on with the troubleshooting. One item I would check is the circuit breaker; it is a bimetal circuit breaker. I have seen these fail from corrosion and age. The heat from the engine or heater could be tripping this if it is bad.

 If you have a fuse buddy, use an alligator clip on each side and jump around the breaker, be sure to have a fuse or breaker in your jumper to avoid any damage to the wiring. Then give it a test and see if it works when you drive the car and it is warm 

Another thought is key on and operate the windows open the doors and give them a try basically you are moving the wires in a high wear area to help find a short. The power seat is another area if you have one, could be a wire pinched after going down the road. If you leave the key on for troubleshooting very long you might pull the power wire for ignition to prevent damage to points or your electronic igniter.

 

One last item I use is  a headlight wired up with alligator clips as a test tool, I use this to test wiring to see if it can carry amps to operate circuits. I have found voltage and  little to no amps cause problems like this. 

Steve    

Let us know what you find 

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One last item I use is  a headlight wired up with alligator clips as a test tool, I use this to test wiring to see if it can carry amps to operate circuits. I have found voltage and  little to no amps cause problems like this. 

Steve    
 

Yeah - better said.   ——————————————^

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  • 2 weeks later...

I once had an issue on one of my cars after installing an electronic ignition kit.  After finishing, I started it 4 times in a row.  No problems, but the next (5th) time there was nothing.  I had volts everywhere, but no start.  Got a new starter relay and it did not change anything.  In looking at all possibilities, I looked at the battery terminals and cable ends.  Nothing really wrong, but I did spy the edges of a thin coating of gunk between the terminals and battery posts.  Got out the wire brush post cleaner, cleaned both side of things on both terminals.  Put it back like I found it and the starter worked and the engine ran again.  End of problems.

 

Apparently, that thin layer of accumulated gunk between the terminal ends and the battery posts would allow volts through, but no amps?

 

I later discovered that on modern systems, dirty terminals will knock the system's volt output down about 10%, fwiw.

 

Just my experiences,

NTX5467

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