No High speed fan

HVAC, heating, cooling, air handling. Anything air temp related.
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v8famvan
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Re: No High speed fan

Post by v8famvan »

I've been testing the wrong @#$%@#$ relay!

#-o I hate when that happens - & it does happen to everyone.

I do this kind of trouble shooting every day, so I will try to walk you thru it.
It is not your blower motor resistor, so don't replace that.
If you unplug your (newly located) high speed fan relay & put a jumper wire across the 2 large wires (red to purple) your fan should turn on high speed. This is the output side of the relay & the terminals we are looking at are #87 & 30.
If it does not turn on, you have a power supply problem from the junction block thru the fuseable link to the relay. Check for power on that red wire (#87) - should have battery voltage available there.
If it does turn on, you have a control circuit fault - meaning there is no power on the orange wire when the fan speed it turned on high (or you have poor ground). Check the terminal #86 (orange wire) at the relay for battery voltage when the switch is turned to high speed.

Hopefully this gets you started in the right direction.
James from B.C.
1992 Safari - R.I.P.
GM Grand Master Techncian

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NotDadsW41
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Re: No High speed fan

Post by NotDadsW41 »

Finally back to this! <sigh>

So I have battery voltage to the orange wire when the switch is on HIGH. If I jumper across the the orange wire to the purple OR take direct from the battery to the purple wire it works.

However, going from the red to the purple gets me nothing. I have only partial voltage here. Usually under 9v. So I guess I have some resistance in that wire somewhere? What else would cause that to bleed of voltage?

I don't think it's the ground that is bad since I am testing the orange wire at the same ground point on the relay.

Thoughts?
CD_S
1991 W41
1995 Astro - Now gone, I am Astroless.
1997 C1500
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1997 Bonneville
1998 Olds 88 LS
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NotDadsW41
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Re: No High speed fan

Post by NotDadsW41 »

So after taking the battery out and fiddling with the junction box it's worse. I removed the bolt under this red cap. Cleaned it all up and put it back together. Now I have less than 1.5 volts at the relay.

Image


BTW that wire is for my headlight relay.

So where is this fusible link that I should be looking for here? I supposed it's painfully obvious of course...
CD_S
1991 W41
1995 Astro - Now gone, I am Astroless.
1997 C1500
1989 9C1 Caprice
1997 Bonneville
1998 Olds 88 LS
http://forums.b-body.org - newly updated!

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NotDadsW41
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Re: No High speed fan

Post by NotDadsW41 »

Now more stumped than ever. After taking things apart and the junction box again, cleaning things, putting a little dielectric grease on just in case and putting it back together, I have battery voltage at the red wire on the relay. When the fan switch is turned to high I have battery voltage at the orange wire. Still no high speed on the fan. I took a jumper and if I go across the orange to the purple, the fan spins up to high. If I go across the red I get nothing. How can this be?

So I put a DVOM on the red again and get battery voltage. Hmm... So I carefully got the DVOM on the red and ground again, shows battery voltage, while I jumper from red to purple at the same time, voltage drops to 1.5v on the red wire...

Is this telling be that fusible link is bad now? And is this that link?
Image
CD_S
1991 W41
1995 Astro - Now gone, I am Astroless.
1997 C1500
1989 9C1 Caprice
1997 Bonneville
1998 Olds 88 LS
http://forums.b-body.org - newly updated!

Topic author
NotDadsW41
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Re: No High speed fan

Post by NotDadsW41 »

Still stumped here guys.

I replaced the pigtail that goes into the power distribution block. See the photo above with 4 wires going into it? That's the one. One of those was cooked. The far right one. Now I have full battery voltage to the relay all the time. :cheers: I can jumper from the red wire to the purple wire and the blower motor will start up on high. WooHoo!

I measured battery voltage on the red wire. I measure battery voltage to the orange wire when the switch is on HIGH. I measure varying voltages to the blue wire through the positions. It goes from 1=11.43 to 2=11.55 to 3=11.77 to 4=11.43.

But when I put the relay in place...the fan will not go on in HIGH but all the other speeds work. WTH?

Does the blower motor have a high speed winding that has failed?

What else am I missing here? Anyone???
CD_S
1991 W41
1995 Astro - Now gone, I am Astroless.
1997 C1500
1989 9C1 Caprice
1997 Bonneville
1998 Olds 88 LS
http://forums.b-body.org - newly updated!

Topic author
NotDadsW41
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Re: No High speed fan

Post by NotDadsW41 »

Umm.... Yeah.... Do you know what I hate more when things break?

When they start working again for no apparent reason!!!

Took the relay out again. Tested all the voltages again. Got the same results. Jumper the purple to red again, got the same result... Shut every thing off. Put the relay back in place and tried it again and it all WORKED. ](*,) ](*,) ](*,) ](*,)

I tightened everything down, closed the hood, backed it out of the garage and it all still worked.

So.... fingers crossed I guess.
CD_S
1991 W41
1995 Astro - Now gone, I am Astroless.
1997 C1500
1989 9C1 Caprice
1997 Bonneville
1998 Olds 88 LS
http://forums.b-body.org - newly updated!
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v8famvan
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Location: British Columbia

Re: No High speed fan

Post by v8famvan »

Image

So where is this fusible link that I should be looking for here? I supposed it's painfully obvious of course...
Yup, that connector with the 4 wires coming out of it is the fuseable link assembly. If you look at those gray wires you will see that they have the words printed right on them. You will also notice that the wire changes in about 4 inches to a different color.
NotDadsW41 wrote:Umm.... Yeah.... Do you know what I hate more when things break?

When they start working again for no apparent reason!!!

Took the relay out again. Tested all the voltages again. Got the same results. Jumper the purple to red again, got the same result... Shut every thing off. Put the relay back in place and tried it again and it all WORKED. ](*,) ](*,) ](*,) ](*,)

I tightened everything down, closed the hood, backed it out of the garage and it all still worked.

So.... fingers crossed I guess.
I suspect that during all your testing you managed to spread a terminal in the connector too wide & caused it to have a poor connection. I would have a look at the terminals in the connectors & check them because poor contact = excessive resistance which = heat which = burnt terminal.
James from B.C.
1992 Safari - R.I.P.
GM Grand Master Techncian

Topic author
NotDadsW41
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Re: No High speed fan

Post by NotDadsW41 »

Thanks James! I will go take a closer look at those terminals on the relay!
CD_S
1991 W41
1995 Astro - Now gone, I am Astroless.
1997 C1500
1989 9C1 Caprice
1997 Bonneville
1998 Olds 88 LS
http://forums.b-body.org - newly updated!

hbastro1994
I am merely driving my van
I am merely driving my van
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SOLUTION to "No High speed fan"

Post by hbastro1994 »

I have a 1994 Astro van an have an issue with "no high speed fan" all other's function. My relay does work when I select high speed at the fan switch on climate control. But, the 12 v that is supposed to be transferred to the blower motor is present, but, it apparently lacks the current to run the fan. If I connect the 12 v positive battery voltage to the blower and leave the ground wire connected i get the fan to run on high speed. So now I left with having to back trace the large red wire on the relay back to the fusable link and junction block (which you have confirmed it's location, thank you very much!), and try and confirm if there is a bad (weak) contact connection which is prohibiting full current to flow.

Below i have listed my trouble shooting to date.

NO CHASSIS/BATTERY GROUND ON BLOWER MOTOR?
I've noticed that the ground lug (and blower case) are not electrically connected to chassis ground (battery ground). The blower motor's case appears to be isolated from the chassis . Hmmm? How can the fan operate on all other speeds but not the high speed, especially if the blower ground is isolated from the chassis (battery ground)? On high speed, there is voltage on the relay side, and the relay is activated. I shorted this red wire to the purple wire (which attaches to the blower) so as to eliminate the relay, but, nothing happens! It seems that there is not enough current to run the fan on high mode. Something weird in this supposedly constant hot (12v) side of the relay. While I had engine set to 'run' and climate control fan set to 'high' I tried to get the fan to run in 'high' by also connecting a ground from the chassis to the ground side of blower. STILL, THE BLOWER WOULD NOT RUN AT ALL! So if its a ground issue why wouldn't the blower work when I applied this ground? Interestingly, if I unplug the ground from the blower and check for continuity of it to the chassis (battery ground) it is shorted/connected. So to recap, I only have chassis/battery ground connected through ground wire which attaches to the blower, but, no ground from blower case to chassis/battery ground. What am I not seeing? 

Also, does the cpu/pcu supply a 'bias voltage "to the 'always hot side of the relay?" If it did, this could account for no high current to operate the fan on high speed. But, I eliminated this possibility by using my test lamp at this red wire on relay to ground and it did not light. 

UPDATE: HIGH SPEED FAN CAPABILITY CONFIRMED. 
I was able to confirm blower motor does work at High speed by connecting the positive side of the battery directly to the fan. I disconnected the purple wire from the high side of the fan and left the black ground wire plugged into the fan. SO, THIS PROVES THAT THE 12V ON THE RELAY SIDE IS NOT ABLE TO SUPPLY THE CURRENT NECESSARY FOR THE FAN TO OPERATE THROUGH THE RELAY. THE ISSUE NOW IS TRYING TO FIGURE OUT WHERE THIS RED WIRE GOES. THE SCHEMATIC SHOWS THERE IS A FUSILINK IN SERIES GOING BACK TO A "POWER DISTRIBUTION, JUNCTION BLOCK.

SOLUTION!:
I found another link within this website I believe his name is James from B.C. 1992 Safari - R.I.P.
GM Grand Master Techncian. James was very helpful, in that he had some pictures and information explaining the location of the Junction/fusible link. I had to remove my battery to access it. Then I was able to unplug it and found the culprit. It was the far right female plug (BURNT, (Dorman 645-906 Blower Motor Resistor Pigtail), which I ordered from Amazon for $18 shipped. Now I need to install it. I'm still in a quandary as to why the blower motor's case is isolated from chassis ground.
It did take me a awhile to get familiar with this issue. Hopefully, this info will help save someone else a lot of time.

eVANder
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Re: No High speed fan

Post by eVANder »

For anyone wondering and with the same issue: Blower does not work on HI (high/max) but works on the first three...

I just solved my issue after some mild frustration. My case was exactly like the one above.

Bought car (2003 GMC SAFARI) with NONE of the climate control features working at all, except for rear defrost. First thing I did was locate the blower resistor connector and found it was burned up. I ordered a new resistor and blower motor. I installed both and everything worked EXCEPT the highest fan setting, aka "HI"

Then after some reaserch I was able to find the burned connection (same one mentioned above) on the other resistor connector, the one in front of the driver side firewall behind the battery. It connects 4 wires. The culprit is the thickest wire. It is RED coming out the firewall but after the connector it becomes ORANGE.

...I found a burnt connector there so I just bypassed it for that wire and spliced in a section. Now it works.
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