Blower Motor acting weird and now truck will not crank. M1008A1

[Tinstar]

A few days ago I had the blower motor on Hi and all was normal for a few minutes and then the blower motor quit and the GEN1 light came on. Drove home and parked truck.
Next day, same thing, but this time I left the switch on Hi and after a few seconds, the fan came back on and GEN1 light went out.
Does it on all three speeds. Voltmeter is normal and needle never moved a bit.
Fan works fine on all three speeds with no motor noise and cage would spin with no abnormal resistance.
It's a Dayton brand.
I removed blower motor to inspect it closer and all was fine with no burnt smell or mice issues. Resistor looked good and connections tight. Have brand new ACDelco fan resistor to install later.
With resistor plug removed, the fan still works on Hi only.
Blower fuse is the required 20A and is good, with no sighs of it getting hot. verified by touch also.

Today, same thing. Started truck to move it and per normal, started fine. VM was normal, fan did same thing and once I was finished, with engine warmed to normal temps, turned off truck.

Half an hour later came back out and attempted to start truck. Nothing. No click, Clunk, or otherwise.
I do get all the normal dash lights when I turn on the ignition. GEN1, GEN2, etc.
The fan works and If I turn the key to the start position, the fan stops and the GEN1 light goes out and nothing from starter. VM needle doesn't move.
Turn key off and back on, get all lights again and fan works, and does same thing, fan stops, GEN1 light goes out and starter doesn't engage.
All fuses in the fuse block are good and no signs anywhere of anything getting hot.
New ACDelco Dash blower switch was installed about 20 months ago.


The GP relay on the firewall works same as before.
The DogHead relay was done as soon as I got truck and has been flawless for over 2 years.
I have not put a voltmeter to it yet as the Mosquito's were tearing me up. Will be doing that of course.


Searched the TMs and it doesn't cover what's happening.
Same with old threads.

I was looking at the TM Cab Ingition and Heater wiring diagram and don't see how they are connected.
Followed the brown wire from fuse block to resistor and see what looks like a 50A fuse (fuselink?) inline somewhere.
Is it buried up under the dash or on firewall side?

I physically checked all the fuse links behind the battery and pulled on each one. They are solid.
What am I missing to check?

Edit: I did adjust/wiggle shift lever just in case the parking switch was the issue.
No effect.



Ideas anyone??!!

 

[m38inmaine]

I have seen the fusible link going to the 12v firewall block partially burn and still show 12v but not carry full load. You can try running a good size wire direct from the battery to that block, that will eliminate a bad link.

 

[Tinstar]

Checked that one physically and it’s fine.

The fan and no start are somehow related.

 

[Tinstar]

Just checked the starter relay with a voltmeter.
25.08V (engine off) on red wire.
Nothing on the others.
Same readings when turning key to start position.

Edit:
Voltmeter shows GP relay functioning normally

 

[Tinstar]

Made a Jumper and jumped the starter relay terminals.
Fired right up.
Relay went out.

Will get a new one.

Still troubleshooting blower motor issue.

 

[Tinstar]

Installed new blower resistor and fan doesn't work after a bit.
Doing same thing.
Fan comes on and works fine, then quits and GEN1 light comes on.
Alternator works fine and when GEN1 light is on, Dash VM is still reading fine.
VM check on the alternator itself at idle and the reading is fine.

Other than checking the fan switch itself, which is next, what am I missing?

 

[Bighorn]

If you touch your voltmeter lead to the fan housing and the other to ground while the fan is on and working vs when it quits; what value do you read?
I am wondering if you have a bad ground or bad power connection somewhere that is causing the problem.
I tried to duplicate it on my m1009.
Since you replaced everything but the housing itself ; through which the blower motor is grounded, I am thinking that would be a place to look.

 

[cucvrus]

Checking the fan switch. That is the only thing you are missing. What starter relay went out? Fan switches are known for trouble. They get a bit loose and heat up at the connection.

 

[Tinstar]

The Doghead relay one.


If the fan switch is bad, would that make GEN1 light come on when turned on?

I’m not seeing it in the TM schematics so far.

 

[Tinstar]

If you touch your voltmeter lead to the fan housing and the other to ground while the fan is on and working vs when it quits; what value do you read?
I am wondering if you have a bad ground or bad power connection somewhere that is causing the problem.
I tried to duplicate it on my m1009.
Since you replaced everything but the housing itself ; through which the blower motor is grounded, I am thinking that would be a place to look.

Will do this tomorrow.

Perfect timing of course!
Doing concrete work tomorrow and have green M101A2 loaded with concrete bags.
Now this.......

 

[cucvrus]

The Doghead relay one.
View attachment 704809

If the fan switch is bad, would that make GEN1 light come on when turned on?

I’m not seeing it in the TM schematics so far.

I have nothing to say about the starter relay.
Yes a bad switch/plug for the fan can make the Gen 1 light. I would not worry about it as long as it is charging. Go do your work for the day and fix it on Monday. Also check the very top fuse in the fuse box. I had a good fuse ut it was a bit tarnished and corroded and not making good contact. Good Luck. Report back. I am on my way to Rausch Creek for the day. Report back on your findings. But I would just run the truck for the day.

 

[royalflush55]

Check the two fusible links that connect to the 12 volt diamond by the glow plug relay. Pull on them real good. Make sure nut is tight on stud. If still ok take them off the stud on the diamond and clean good. Reinstall with dielectric grease and tighten. Hope you can get it going.

If your starter relay did go out at least you didn't have a starter run on and burn up the starter!

 

[doghead]

Made a Jumper and jumped the starter relay terminals.
Fired right up.
Relay went out.

Will get a new one.

Still troubleshooting blower motor issue.

If you simply jumped the two large wires and it cranked, all you proved is there is 24v supplied to the relay.

If you supplied the small stud(wire) with 12 volts, and it cranked, then you proved that your ignition switch is not suppling power.

"Jumping" either way and getting it to crank, does not prove the relay is bad.

Just checked the starter relay with a voltmeter.
25.08V (engine off) on red wire.
Nothing on the others.
Same readings when turning key to start position.

Edit:
Voltmeter shows GP relay functioning normally

If you are not getting power to the small wire when your key is tuned to crank, then your ingition switch is not getting power to the relay.

This could be your ignition switch or more likely a bad connection or fusible link supplying it.


Your 2 problems probably stem from one issue( a 12 volt sourced supply). Maybe in your fuse box? Maybe a bad fusible link?

 

[Tinstar]

Check the two fusible links that connect to the 12 volt diamond by the glow plug relay. Pull on them real good. Make sure nut is tight on stud. If still ok take them off the stud on the diamond and clean good. Reinstall with dielectric grease and tighten. Hope you can get it going.
If your starter relay did go out at least you didn't have a starter run on and burn up the starter!

I did that yesterday and physically checked every fuse link.
Already applied Electrical grease to everything and made sure all connections tight.
Hands on checking everything, not just looking.

 

[Tinstar]

D

If you simply jumped the two large wires and it cranked, all you proved is there is 24v supplied to the relay.
If you supplied the small stud(wire) with 12 volts, and it cranked, then you proved that your ignition switch is not suppling power.
"Jumping" either way and getting it to crank, does not prove the relay is bad.
If you are not getting power to the small wire when your key is tuned to crank, then your ingition switch is not getting power to the relay.
This could be your ignition switch or more likely a bad connection or fusible link supplying it.
Your 2 problems probably stem from one issue( a 12 volt sourced supply). Maybe in your fuse box? Maybe a bad fusible link?

Was thinking about that last night while looking at TMs.
That it’s more likely Ignition/fan switch or ??
But will do testing tomorrow. Busy today.

I’ve physically checked all the fuse links under the hood.
All are solid.


Haven't dug into the Dash yet except fuse box.
The Dash wiring harness was replaced with a new gm one not long before I bought truck.
No black goo on it and all fuse slots shining bright.
All fuses are good and verified with VM
Nothing getting hot.

Where is that 50A blower fuse/fuselink thats shown in the TM heater wiring schematic located?
Brown wire
Behind instrument cluster or glove box or??

 

[royalflush55]

At this point I would suspect ignition switch.

 

[joshuak]

...Where is that 50A blower fuse/fuselink thats shown in the TM heater wiring schematic located?
Brown wire
Behind instrument cluster or glove box or??

I looked on a spare wiring harness, and could not find one. Solid wire from the heater control plug to the fuse block, I think the TM is mistaken in this case.

Pic of similar plug at heater control


Pic of the wire.

 

[doghead]

Use a meter to measure resistance, to test the fusible links.

 

[doghead]

Also, test your small signal wire to the underdash relay for 12volts when the key is in the crank position.

 

[doghead]

Also, check the bottom most fuse.

Also, I'm wondering if the suppressor on the blower motor may have shorted to ground. It can be eliminated.

Not sure about the yellow wire on the schematic showing a 50 with it.

The more I think about your issues, the more I think you have a bad fusible link, wire or connection on a 12v wire feeding the ignition switch and or the heater fan.