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Power windows INOP…fuse box problem?

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colokevin

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I have a 1990 V1500 Suburban with power everything. I ripped out the interior, including all electrical, and am slowly rebuilding/reinstalling everything. Everything electrical works fine, EXCEPT the power windows. Ignition, power door lock, lights are all good. Obviously I've tried all 4 window switches when the ignition is in ACC or RUN positions. I'm not the best at electrical gremlins, but I'm learning. On the fuse block, I tested the both WDO cavities, no current. I tested the PWR WDO circuit breaker cavity, no current. I tested the HTR A/C and AUX HTR A/C fuse cavities (which are both supposedly connected to the PWR WDO cavity, per the factory wiring diagram), no current. I've tested other nearby cavities and my test light works as it should, so I know my test light has a good ground. I'm honestly out of ideas! Why isn't power getting to the fuse box?
 
I'm a bit confused, how does your heater/AC/rear AC work if there is no voltage on those circuits?

*IF* you made a mistake and those don't work either, then I would verify by the wiring diagram if a shunt is used for those, and make sure it's not bad, and the connections on it are good. If no shunt, and every fuse terminal connected to power windows doesn't work, it may be the wire has broken off the back. Not likely, taking the fuse panel in half would be one of the last things I'd want to do, but if everything else is powered that comes in off of both fusible links, then the problem exists between the fuse panel engine compartment connector, and those fuse terminals, and that's only a wire, the fuse terminals themselves, and maybe a shunt.
 
On the firewall, just left of the brake booster and up high, is a two post positive bus. It has a wire from the battery and a wire leaving it. What is that for? I re-did all my wiring so it's completely different. Just wondering cause I thought the HVAC was connected to that. Dunno
 
Some trucks used that junction block as a power source for things like a tailgate power window,also I "think" if I recall right there is a wire off it that sends juice to some of the fuse box circuits..you'll notice it has a shunt across it connecting the two studs together,which can melt if an overload happens...GM truck junction block.jpg
 
YES, thanks Bob. Not that I'm sure it's the problem, just that it could be the problem
 
dyeager, sorry to confuse. I haven't hooked up my HVAC yet, so I don't know for sure if it works or not. Since all 3 circuits (WDO, HTR, AUX HTR A/C) are powered by the same feed, I assume that it's not going to work either. I do have the junction box/positive bus mounted on the firewall. The shunt between the wires seems good; so does the 1 fusible link that I found coming off it (white/opaque, cylindrical plastic part). It all seems intact, although I've never seen a blown fusible link. Is there another fusible link (beside at the starter)?
 
Get your wiring diagram (might as well grab the service manual and parts manuals too) here http://67-72chevytrucks.com/vboard/showpost.php?p=5621043&postcount=1

Yes, there are two fusible links. Both of them are "before" that junction block on the firewall, but I don't recall where both reside. They generally control two separate "sides" of the vehicle, if one burns out, the lights won't work, I believe the major affect on the other link is no ignition power.

The shunts I'm talking about are on the fuse panel. If you'll look at the wiring diagram from the above link, and find the fuse panel portion, you'll see how the shunts on the fuse panel work. I don't believe the circuit breakers on the panels control what you are dealing with, not sure if the power windows are on a relay or not. I know the power door locks are.
 
OK, I checked the shunts in the fuse panel; they're all good. Plus, they aren't part of the window circuit anyways.

I just jumped the WDO circuit to a fuse cavity that I know is hot and all the windows go up and down from the door switches. At least I know that the problem isn't anywhere in the window circuit, switches, or motors.

Seems to me that the back of the fuse panel isn't getting power to this circuit.
 
I was wrong, one of the 30A breakers on the fuse panel is for the power windows, which you said had no current. Did you remember to check it with the key in "run"? I forget that all the time.

If I'm reading the manual correctly, the left leg of the circuit breaker cavity should have 12V with ignition on. Should have 2 of those breakers on the panel, swap them for an easy test.

No idea why, but they also list power windows on the accessory terminals across the top, separate of the power rear window option, so no idea if you've got anything plugged in up there.
 
Yes, there are 2X 30A circuit breakers. I replaced both with new ones recently. I have been testing in ACCY and RUN. Good question though. Never assume the obvious.

I agree. It looks like the "300 ORN" ignition feed powers the "250 BRN AUX HTR A/C" circuit, which is connected by the left leg to "50 BRN HTR A/C" and "76 PNK PWR WDO", then back up to where the 2 power window circuits plugs in. All 3 of these circuits have no current even with the ignition ON.

I do have the power window circuit plugged into the cavity 4th from the left/ 2 down. Both the PWR WDO cavities are wired together; one for regular power windows, the other for the tailgate window on equipped vehicles (mine has ambulance doors.) I don't have anything plugged into the tailgate power window cavity on the top right.

All of this leads me to believe that the "300 ORN" ignition wire/connection is where I should be looking. Do you suggest I remove the fuse block from under the dash, pull the halves apart, and hunt around in that mess? I'm not even sure that to look for other than loose connections or fried wires. Any ideas?
 
Without looking at the rest of the diagram on my end, does that orange wire (300) come directly off the ignition switch? I imagine it should. I'd check the ignition switch before pulling the panel apart.

I've seen ignition switches that are bad (the contacts burn on the inside) and I've heard of burned wires inside the fuse panel. Ignition switch to me would seem a more likely failure mode, but if you know 12V is coming into the panel from wherever 300 originates, then that would point directly to the panel.
 
Yep, digging more into the diagram, C300 does go direct to the ignition switch, which has caused me some problems recently. I'll bet that's my problem. We'll see in the morning…
 
Problem solved! It was just a loose connection on the ignition switch on the top of the steering column. Pushed it in hard and all the windows work now. So excited that I rebuild the driver's vent window, replaced all the rubbers, and greased the tracks. Thanks dyeager for helping me work through it.
 
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