Blower motor stalling, can arc point contact relays in a hurry. Either this or replacing them with worn out relays.
Back in the 60's was working with Bell Labs on touch tone, got to visit many of telephone exchange locations using literally thousands of relays with full time crews constantly reburnishing the contacts. That's when I learned how to burnish contacts, been doing this ever since. Haven't found a relay yet where I can pull off the cap. Even riveted on tungsten contacts that last a heck of a lot longer.
But don't do this anymore, used up my supply of tungsten contacts. Wish I grabbed another handful when I had the chance. One insignificant bit of carbon arcing can prevent good contact with these things.
See you can have also a front and rear blower motor, which one? As late as the 70's could buy a set of new brushes for a quarter, and new bushings for a dime a piece. Long ago history, is two tiny oil wicks in there that hold some motor oil that dry up. First the got rid of the two screws that hold the motor together and spot welded these. Could work around this by drilling those spot welds out and use short sheet metal screws.
Use to use a nut to hold the blower motor on, then a pal nut that could be pressed off, can't use that anymore, blower wheel is heat pressed on, so can't even oil those wicks. Another name I have given this squirrel cage blower motor wheel is a leave chopper. This can also cause motor stalling. And not really an evaporator, but a cabin filter, can find all kinds of debris on the face of these blocking air flow.
Typically, the first thing to go with a stalling motor are the limiting resistors, high speed relay is the last to go. Typically high current motor draw is in the 20-24 amp range. Any aftermarket motor I have tested was in more of the 16 amp range for very unsatisfactory performance.
If they would add those two screws and a pal nut to hold the wheel on, could be a repairable motor, mostly need cleaning, new brushes, and bearings. But now the entire blower wheel and motor is a throwaway part. No way possible to remove that blower motor wheel, and if you did, would never get it to hold on again.
Well this wasn't the only problem, instead of using copper bars for the commutators, switch this to copper foil. Also has a rubber tube for a brush cooler, that can be packed with debris if not rotted away first. Good ones at rockauto.com are 80 bucks each.
Major change in these motors was the development of the ceramic permanent magnet. These can be cast and baked. magnetized after the assembly.
Before this, the pole pieces for the field had to be hand machined and a coil of wire wrapped around them, and had four wires to assemble instead of just two. Were in series with the armature so heavy additional copper wire had to be used. Even at this in the 70's the dealer price for a new motor was six bucks. For this much cheaper motor, well over a hundred bucks today.
But not quite as bad as my local Toyota or Honda dealers wanting over 250 bucks for there POS motor. Still think about the old days when you could buy a complete rebuilt kit for a fuel pump for a buck. Look at fuel pump costs today! Even doing the work yourself, cost a small fortune. Another piece of crap motor with ceramic permanent magnet field cores and a super cheap armature using plastic impellers. Then you have to drop the tank to change it with really no good means to drain it first.
Wiring schematic might help. Might want to check the 30 amp fuse that is under the hood that supplies power to the blower motor when it is in high speed. Check and see if has blown. There are two fuses for this setup. a 20 amp in the instrument panel block for the lower speeds and the 30 amp for the high speed under the hood fuse block.
toolhawk: You are talking about the blower motor for the front that is acting up , are you not? Do you even have a blower motor for the back in this vehicle?
The suggestion that I gave is for the front blower motor fuse. It is a 30amp fuse that is the orange hot wire going to the blower relay for the front high speed.. If that is good then you will have to do look at amp draw on motor, wiring connections, etc like the other mechanics on this site suggested.
Sorry old man, in the schematic, looked like a ground, if you say it is a hot wire, that blower is toast.
If rear blower is giving amps also, would look elsewhere.
@old man, maybe the orange is shorted to ground. But, hey, never know with these old vans. But that was awesome advice. Last I fixed an astro, was in 03 :thx :ROFL I hate these vans, but good for soccer moms.
But will stand but what I wrote, need to check amp draw and eliminate the blowers, after that, check the I/P.
Nice to see a color coded diagram, but a white wire on a white background is a bit difficult to distinguish. Indubitably, C2 is connected to C3, so the blower is off with the mode switch. Could have easily put that off on the blower switch. My P-30 is this way, if I want to switch off the blower, have to move the mode lever to the Off position.
In the process, if the engine is running, will briefly turn on the AC for extra wear and tear. So switch off the ignition first before moving that lever.
Other vehicles besides having that off position on the blower motor switch, also use slightly more robust contacts on the ignition and blower switches. So no need with that high speed relay, that certainly beside being a PITA is more expensive. Besides this, if those contacts weld shut, and they do, being always hot can discharge your battery.
I try my best not to think about whatever that idiot that designed this was their logic, this will give me a headache. Not easy to change, so just have to learn to live with it.