1987 1500 silverado window problems.

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Andrew Hayes

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I have a 1987 Chevy Silverado with a 5.7 350 TBI and having problems with the passenger side window. The passenger side switch works great but the driver side switch will not let the passenger window go down, when you hit the switch to lower the passenger side window the motor bogs down and the lights dim, but the driver side switch will raise the passenger side window great.

I have replaced both switches and the passenger side motor and both switch connectors.

What do y'all think the problem could be? I'm thinking electrical problem but have looked that far yet.
 

HotRodPC

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I have a feeling it's going to be a current draw problem, maybe due to a tired window motor in the passenger side. :shrug:

Something @chengny is probably better to diagnose or have some info about.
 

Andrew Hayes

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Thanks. I replaced the motor years ago with very little use, the motor works great with the passenger switch and going up with the driver side switch, the driver side switch just won't let the motor go down. I replaced the driver switch and still the same problem.
 

HotRodPC

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it could also be the connector at the driver side switch.

Does it even try to move it all? Or just nothing at all like it's not even connected?
 

Andrew Hayes

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When you try to lower the window the engine bogs down and lights go dim but the motor doesn't do anything.
 

chengny

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I have a 1987 Chevy Silverado with a 5.7 350 TBI and having problems with the passenger side window. The passenger side switch works great but the driver side switch will not let the passenger window go down, when you hit the switch to lower the passenger side window the motor bogs down and the lights dim, but the driver side switch will raise the passenger side window great.

I have replaced both switches and the passenger side motor and both switch connectors.

What do y'all think the problem could be? I'm thinking electrical problem but have looked that far yet.


First, just to make sure I have everything straight:

1. Only the RH window has a problem - the LH window is okay

2. When the local (RH) switch is used to operate the RH window, there is no problem - going up or down.

3. If the remote (LH) switch is used to operate the RH window; it can be raised normally (just like with the local switch). But, if you try to lower the RH window from the remote switch, it fails to respond. However, even though the window doesn't move, it seems as it is being supplied with power because the lighting dims and the "motor bogs down".

Since the motor operates fine in both directions when power is supplied by the local switch - and in the raise mode from the remote switch, it is likely that there is reduced voltage available for lowering (from the remote switch). It's also possible that the motor isn't getting a good connection to ground - when in the lower mode.

When the LH switch is toggled to the DOWN position, 12 VDC is supplied from that switch to the RH motor on the TAN lead and the DK BLU/WHT lead provides the path to ground. When the LH switch is toggled to the UP position, current flow through those two leads is reversed - now the DK BLU/WHT is hot and the TAN lead goes to ground.

The initial diagnostic check would be to see if that is the case (i.e. TAN hot & DK BLU/WHT grounded) while holding the driver's side switch in the DOWN position.

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gmachinz

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More than likely you have a break in the wiring in one of the door jamb boots which is pretty common if everything else looks fine.

As stated before, verify with the LH switch for the RH window is pushed down, that tan from LH switch is hot via a test light at the RH window switch. Then also verify the dark blue w/white is grounded. To do this use a mutli-meter set on OHMS and probe one lead to ground and thebother on the dark blue w/white wire @ the RH switch-if it is a good ground there should be continuity-if not, there a break in that wire.

If it is to be assumed there is a break, perform the same ground test @ the RH dash harness connector located above the kick panel-keep working thisnprocess backwards towards the LH switch-once you get continuity, you've at least isolated the section with an open ground.
 

chengny

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The thing is, the DK BLU/WHT lead (between the LH & RH switches) can't be open. If it were, when the driver's switch was toggled UP, it would be unable to supply power to the RH motor.

I think what he's looking at is a ground fault in the TAN lead.

If the TAN has a fault to ground (but not enough to trip the breaker) and the LH DOWN switch is closed, some degree of the total current available from the switch will flow into the chassis - and not to the motor. Due to the reduced current to the motor, it will struggle to operate - and appear to "bog down". Also, if this condition existed, it would cause a drop in total system voltage - and the lighting would dim.

But on the other hand, if a ground fault does exist in the TAN lead, that condition would have no effect on raising the window. Since - when the window is being raised - the TAN lead assumes the role of the ground, a fault to ground in it would not hinder motor operation. If anything, due to the decreased resistance in the ground path, it would probably increase the speed of the motor.

I was going step by step on this. First was the initial check of power on the TAN and continuity to ground on the DK BLU/WHT - with the remote switch toggled DOWN. Next was to suggest a check for a ground in the TAN with the LH switch in the neutral position.
 
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Andrew Hayes

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thanks to everyone who has guided me to where to look for the problem, I will let you know what I found out cauing the problem.

Thanks again.
 

gmachinz

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Lets clarify-the OP only has an issue with the LH switch controlling the RH window going down. This means in that state, the tan is hot and the dark blue w/wht stripe is grounded to the chassis through the LH master switch. All window leads are normally grounded @ rest and we know the RH switch works perfectly fine so Im merely showing exactly what to test to verify tan is live and dark bkue w/wht is grounded throughout the process.

I suspect "if" there is no bogging down of the voltage, then there most likely is an open circuit on the tan before it gets to the RH switch-if it does bog down, likely there is a near complete break of the wiring or corrosion somewhere creating excessive resistance.

I wouldnt even be surprised if you inspect the wiring inside the jamb boots only to discover the previous owner also had issues and butt spliced wires together-Ive seen that too lol
 

smoothandlow84

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Or....the track for the window could be mis-aligned causing the window to bind up during operation
 

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