1976 - Intermittent blower motor and turn signal(s)

[alfreema]

1976 Chevy C20 Camper Special Silverado with 454
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So for the most part my blower motor hasn't been working at any speed.   Every once in a while it will come on and work at every speed.

I spent quite a bit of time searching here and see that blower motor complaints are common, so with the awesome knowledge shared here I:

a) checked the fuse in the cabin (and the 30A one coming off the junction box while I was at it)
b) rebuilt my switch (took it completely apart and cleaned up the points of contact, then rang it out on a multimeter -- it had issues, but looks great now)
c) swapped out the resistor

After the doing above I got excited when the blower fired up on the first test.  But ... then ... it stopped working again.

I had an 1940's International Cub tractor that taught me that bad grounds are evil, so I started to become paranoid about the ground on my blower system.

And now for the question for you gurus:

The old Chinese motor housing has factory black paint on it.  The ground terminal is just screwed into the housing.  The screw I pulled out was terribly rusted and the plate is a bit rusty where it was screwed in.  Aha!  So I replaced it with a shiny new #10, 1" screw.  Still no blower motor.   I was still bugged by the paint.  I decided to start sanding and finally could see a _little_ metal.  Screwed it together for a quick test and voila!  Blower motor worked when I fired it up.

Now this could be a coincidence and I didn't really solve the problem and tomorrow it will not be working.   

But if this is the problem, how the heck was it EVER working if the plate is painted black at the factory?  Is the only path to ground the contact between the screw and the hole the screw sits in?  As in the threads of the #10 screw contacting the inside of the hole?  I think I must be missing something.

I will sand the sucker down thoroughly so that the terminal itself is flat against clean metal, but for future reference I want to understand this a bit better.

[VileZambonie]

In GM's diagnostic strategy, the first step is checking the fuse and the second step is to check the blower motor ground.

Most people would go check for B+ at the blower and then check the ground circuit. GM knew the poor grounds were an issue, as you can see in their diagnostic strategy steps, they're having you verify the ground integrity before verifying the voltage to the blower. You will find with these trucks that servicing the grounds should be part of routine maintenance. Adding auxiliary grounds can help as well. I usually wire these trucks up with a superior grounding method to factory design.

[alfreema]

Man, so I saw lots of references to B+ and people saying, yeah, they have B+, but I have no idea what B+ means?   Based on your other posts I have come to conclude it means 12V, or whatever voltage the battery is kicking out?

Can you shoot me a link to a post (preferably with pics) where I can see your improved grounding techniques?   I'm noticing a lot of bolts in my truck are starting to get rusty so I am getting concerned that this is going to become a pressing issue throughout my engine.

[VileZambonie]

Yes, you are correct.

I can post pics later this week

[alfreema]

Okay, so blower is now working great by fixing that ground.   So I decided to start thinking through my intermittent left and right turn indicators on the dashboard.  Rarely they will work properly, but mainly just won't ever come on.   Sometimes they come on and blink, other times they come on solid.   Randomness.   That just speaks GROUND PROBLEM to me, so I assume they share a ground somewhere.   Any hints on where I can find a picture of where the dashboard turn indicators would be grounded so I can inspect that?

Hmm, or maybe there are some quick voltages/ohms readings I can check before I assume it's a ground issue?

[bd]

Parking brake pedal frame at left kick panel.

[alfreema]

Awesome!   Hope to dive into it this afternoon!

[75gmck25]

If your '76 is like my '75, the instrument panel ground is a black wire connected to a post on the emergency brake mechanism.  I do not have a ground bus bar like that shown in the picture.

IIRC, each of the turn signal housings has a white wire that is the ground.  In the back of the truck there is a large gauge white wire to ground the tail light harness and its in the middle of the truck up above the bumper.  All of these grounds are subject to road dirt, so its common to have corrosion. 

There is also a (black wire) headlight ground on each side of the radiator support, but I don't think these affect the turn signals.  Also verify that the turn signal bulbs are inserted correctly.  The sockets get corroded and its sometimes hard to tell if the bulb is hard to insert due to corrosion or if you have it backwards.

Bruce

[alfreema]

The picture was helpful, and I found the ground.  The screw looked great and there was no rust at the connection.   I jumped the black lead directly to my battery ground though, just to be sure, and it didn't help at all.   So I can rule the ground out as being the issue.  Interestingly, the right indicator was failing (but I could here a click and the actual turn signals all work), but the left one was working perfectly.

Based on another thread here I popped off the dash and the clear plastic covering the gauges.  I was able to lift the black metal cover just enough to slip the green cover sheets off to expose the bulb.   I tried to use mechanical fingers to grab the bulb but I just couldn't get them to clamp tight enough (they are SUPER old and kinda crappy).   But, low and behold, just jiggling the bulb with the fingers made them start working, even though I don't believe I got it to turn really.

That coupled with @75gmck25's post leads me to believe that possibly the sockets are becoming corroded.

Is there any trick to taking the bulb out without removing the metal instrument cover (do I just need to press it in slightly and turn it a quarter turn)?  I will probably buy some new and better mechanical fingers and try again -- I need a new set anyway.

[bd]

The instrument clusters are plagued by connection issues due mostly to dust accumulation and tarnish.  Remove the sockets with the bulbs from behind the cluster.  About 1/8 CCW turn should be adequate.  Burnish the copper foils where they contact the socket terminals and the IP cluster harness connector terminals using some crocus cloth or a #2 pencil eraser.  Be careful that you don't dislodge the foils from the plastic backing - an easy mistake to make.  Be sure to inspect the bulb filaments while they are out.  If there is any dark discoloration of the glass envelopes, replace them.

[alfreema]

@bd  I'm a bit scared to go that far.   It wasn't obvious how to even remove the black metal cover, let alone anything else preventing me from getting to the bulbs and sockets.   I'll search here and try to find a good description of how to remove all the stuff in front of the sockets, but if you know of a thread, please shoot a link here.

[JohnnyPopper]

bd is making the point that the bulbs are 'designed' to be changed out from the rear of the instrument panel.

Stick your smart phone in there and take copious (many) pics before you do anything.

Analyze the photos and get comfortable with the idea of reaching into a dark space and feeling your way around.

You can do it man!

Let us know how it turns out, please.

[VileZambonie]

Removing the cluster is a very straight forward process. Once you unclip the speedo cable there are two connections that need to be removed to hold the whole assembly in your hand or to lay on the bench. Don't even waste your time farting around with it in the truck. Take the unit out and clean all of the connections using the eraser and cleaning up the tabs as BD described.

[alfreema]

I'm totally doing this.   Been waiting for the weather to heat up.   But now I am wondering ... what about switching to LED.  My truck is bone stock.   Or at least as bone stock as I have been able to keep it.   And I love it that way.   But is there a compelling reason to switch to LEDs in the dash?   Is it worth it?   Why should I, shouldn't I?

[bd]

Begin by making sure that all of the instrument lamps illuminate properly before converting to LEDs.  LEDs can introduce low-load and reverse-polarity circuit conflicts that complicate diagnoses in cases where preexisting problems exist.  When converting to LEDs a load resistor may need to be added to the dash lamp circuit so that the dash dimmer rheostat correctly dims cluster illumination proportionately across the full rotation of the dimmer knob.  Ultimately, you will be very pleased with a good quality LED conversion.  They are far brighter than the OEM 194/168 bulbs.