92 Astro blower will not run in High

My 92 Astro AC blower will not run in High, I replaced the blower motor, Relay and resistor Twice first time autozone second time GM :banghead: All other speeds work fine. At the relay the hot wire Red #2 from the fusible link has voltage as it should untill I switch to high. Then the voltage at the red wire cuts off. and there is no out put to the motor puple wire #65. I have performed the electrical diagnosis in the OEM electrical manual and it leads me to the relay. I have opened up one of the relays and the points are closing when high is set but the voltages that should be there is not. All of the gounds check ok.

I have 12 volts across the fusible link grey and orange wire behind the battery untill i switch to high, also if I leave the switch on high the relay gets warm.

Should I replace the switch in the cabin? Any advice would be greatly appreciated.

Thanks in Advance

Without checking the manual...
You've got 12 volts ACROSS the fusible link? Or 12 volts on each side of it?
I had a fuse go high resistance. I had 12 volts at no load, that disappeared with a load.
For odd faults, try using a lamp to check for voltage. They draw much more current than a voltmeter, and can help to find "odd" faults. Also, if you put a lamp across the fuse, and it goes bright, obviously the fuse is bad.
Good luck

Wow you were right :bananasmi :bananasmi :bananasmi I get 12.49 volt reading on the load side of the fusible link but it will not light a 1/4 watt 12v bulb. It will light on the battery side of the same link.

Can I remove the fusible link and put in a fuse holder and a 20 amp fuse.
Or are these links readily available, I chose 20 amp because that is stamped on the fusible link.

Thanks in Advance

To be honest, i haven't seen these fusible links, mine still work....
They don't seem to go too often. I'm thinking since they bolt in somehow, maybe the contact area might be larger than a fuse and holder, and therefore better. They should be available at GM. If it's too pricey, (what, GM?), I'd use a fuse or a small diameter normal wire. (half the size of the load -carrying wire or so, you want it to burn first)
Either will work, your call, unless some-one else has an opinion

I just replaced the connector and 4 fusible links just behind the
battery, problem solved. The part comes as a connector with 4 wires and
4 solderless terminals, Part numbers Delco #PT391 and GM #12102762.
$19.00 at rockauto.com

I have a similar problem, and will try your solution. By the way, how does one get access to the OEM schematics. I have a Chilton's manual, but none of the schematics deal with the blower (Chilton's manuals for my other cars have tended to be hit or miss on schematics as well). Thanks

We've just had a long weekend up here, hense the slow reply.
What year?
My '97 had a fault (repairable) on the "resistor board" inside the heater box.
As for real schematics, I'm at a loss. I use a Haynes manual, but they're not complete either.

Mine is a 92. Great truck, by the way. Last weekend I was in the mountains (without the Astro), and there was a new 4X4 Expedition stuck in a nasty spot on a Jeep road that my AWD Astro navigates with (relative) ease :smooch:

I have a 2000 Safari with a similar problem. It was sitting in the driveway, engine off, and the blower just starting blowing air.

It won't work on any speed but "low".

The only way to get the blower to stop is to unplug the wire running into the blower box. Pulling fuses has no effect.

Is this some kind of resister malfunction?

There are 2 fuses, 1 for "High" and 1 for lower speeds.
So if you pull both fuses, and it still runs, I think you may have to look for chaffed wires, supplying 12 volts from a nebulous somewhere.
It only runs on "Low" and no other speeds?
Odd that the 12 volts only goes to that speed, and not all the lower speeds.
I'd probably pull the resistor board, (in the heater box, behind the washer fluid / overflow bottles), and look VERY carefully at the printed wires for damage. Use a magnifying glass. You might find a carbon track or a broken printed wire.
For a starting point, it's easier than looking for a chaffed wire....
I just thought, make sure you've got a ggod ground. A lot of odd faiults are caused by bad grounds, and again, they're pretty easy to check. (I thought maybe a bad ground might be leaking the "high speed", to look like a low speed fault.)
Good luck

I just replaced the connector and 4 fusible links just behind the
battery, problem solved. The part comes as a connector with 4 wires and
4 solderless terminals, Part numbers Delco #PT391 and GM #12102762.
$19.00 at rockauto.com
I did the same, problem solved :)

Thanks for the help!