What are the chances of 2 blower motors being bad out of the box?

TheBrisbyMouse

New member
May 1, 2021
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In my '84 Oldsmobile Delta 88, I've been struggling with the blower motor since I got it. I've put 2 new ones in, neither worked, and the old one never worked either. I have confirmed with a voltmeter that everything upstream of it(resistor, relay, etc) is working properly, and the ground is good. I even went so far as to use jumper cables to directly connect the ground connector of the motor to the negative battery terminal. None of the 3 motors ever worked, and I'm at a loss for what else it could be. Any help would be appreciated.
 
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GoodOldsGuy

Member
Oct 20, 2020
74
8
Texas
In my '84 Oldsmobile Delta 88, I've been struggling with the blower motor since I got it. I've put 2 new ones in, neither worked, and the old one never worked either. I have confirmed with a voltmeter that everything upstream of it(resistor, relay, etc) is working properly, and the ground is good. I even went so far as to use jumper cables to directly connect the ground connector of the motor to the negative battery terminal. None of the 3 motors ever worked, and I'm at a loss for what else it could be. Any help would be appreciated.
Did any of the blower motors work at any speed? Like only blow low, or a couple low speeds and no high? Or high speed alone?
I can't say for sure what the wiring is like on the 84's, but the older versions had 3 different wires feeding the resistor and another heavy wire (10 gauge as I recall) coming directly from the main power connected inside the conduit that hung down on the engine side of the master cylinder. It's a 30amp circuit and it's hot all the time. The only fuse for it is the fusible link at the starter. All the 30 amp circuit did was supply for high speed blow. It was engaged by the switch on the dash when set to high it engaged the relay to supply 30 amps to the feed side of the resistor (meaning it wasn't resisted at all).
Does your control heat/a/c control panel on the dash have the word "tempmatic" on the lower right side?
The high amp supply wire used to be routed from the conduit across the back of the engine over to the compressor harness, and then back towards the blower relay. It is/was always hot. It used to be very common for the wire to be burned or suffer from some other damage just because where it is. Check it out. That might explain why you don't get high blow. The other speeds were supplied electricity with 3 seperate wires coming from the blower switch, through the a/c harness through the firewall to the resistor. All 3 of them got voltage from the main circuit blower wire from the fuse box to the control panel harness. I believe it is a brown 14 gauge wire that connects by itself (not in a bus terminal, it's a single connector) to the control panel harness. That connector used to come undone or burn up from over loading. It comes through the dash behind the fuel gauge and under the warning light display. Check it out. Without voltage coming in to system there, there will be no voltage going to the relay and resistor, other than the constant on 30 amp circuit to the relay, but it won't engage high blow without the signal voltage from the panel switch to the relay. I'm willing to bet that the brown switch supply circuit has failed, or the connector has come loose from your blower switch, or the harness from the control panel to the relay and resistor has been damaged. Have you looked behind the control panel? It's fairly easy to get loose, but the temperature control cable is a real beach to disconnect so just take the screws out of the control panel and gently pull it towards you so you can see what's going on with the wiring behind it. Be careful because all the vacuum lines for the vacuum motors connects to the back of the panel as well. It's pretty tricky to disconnect and they are likely fragile from age, so leave them attached and just pull the control panel out far enough to see/test the wiring and connectors. I know you said that there is power at the resistor and or relay, but that could be coming from the high speed circuit and will never engage the relay if the power from. The switch doesn't get there as well. I have a Fisher Body manual that has a relatively simplified wiring schematic for the Tempmatic system in 1979. It's probably the same, or close to what you're dealing with. I'll hunt it down, get a picture to post for ya.
I will say that the resistor and blower relay are not uncommon failures. Probably more common than the blower motors themselves, as far as total failures go.
I'll post the wiring later today, but I hope that helps in the meantime.

I forgot to add that you should check all the fuses in the fuse box, and make sure that none of the add on option power connectors has come undone at the fuse box. All those connectors that plug into the fuse side of the fuse box are add on optional circuits. Some are even stacked on top of each other. Loose or disconnected can be easy to miss. And yes, the Tempmatic heat-a/c was optional and it has an add on power supply connector. I'll see what slot it plugged into in 79, maybe it's the same for 84.
 
Last edited:

GoodOldsGuy

Member
Oct 20, 2020
74
8
Texas
In my '84 Oldsmobile Delta 88, I've been struggling with the blower motor since I got it. I've put 2 new ones in, neither worked, and the old one never worked either. I have confirmed with a voltmeter that everything upstream of it(resistor, relay, etc) is working properly, and the ground is good. I even went so far as to use jumper cables to directly connect the ground connector of the motor to the negative battery terminal. None of the 3 motors ever worked, and I'm at a loss for what else it could be. Any help would be appreciated.
One more thing, when you turn the key to ignition ON, the blower should come on at whatever you have the switch set to, but no less than low speed. Low blow is always on when the car is on. It was some kind of safety feature to keep fresh air moving through the cabin at all times with the engine on.
 

GoodOldsGuy

Member
Oct 20, 2020
74
8
Texas
In my '84 Oldsmobile Delta 88, I've been struggling with the blower motor since I got it. I've put 2 new ones in, neither worked, and the old one never worked either. I have confirmed with a voltmeter that everything upstream of it(resistor, relay, etc) is working properly, and the ground is good. I even went so far as to use jumper cables to directly connect the ground connector of the motor to the negative battery terminal. None of the 3 motors ever worked, and I'm at a loss for what else it could be. Any help would be appreciated.
 

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GoodOldsGuy

Member
Oct 20, 2020
74
8
Texas
In my '84 Oldsmobile Delta 88, I've been struggling with the blower motor since I got it. I've put 2 new ones in, neither worked, and the old one never worked either. I have confirmed with a voltmeter that everything upstream of it(resistor, relay, etc) is working properly, and the ground is good. I even went so far as to use jumper cables to directly connect the ground connector of the motor to the negative battery terminal. None of the 3 motors ever worked, and I'm at a loss for what else it could be. Any help would be appreciated.
The post above this one is the pictures I mentioned earlier. I was right, the wire supplying voltage to the fan switch is brown, but I forgot that it also supplies voltage to the low blower ambient switch. That's the switch that makes sure at least low blow is on all the time. That brown wire is circuit number 50, and it's 16 gauge (i had that wrong earlier). Circuit 50 is an add on connector that plugs into "ign 3" on the front of the fuse box. The pic here is another diagnostic flow chart for the blower. God Speed, I hope that helps.
 

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GoodOldsGuy

Member
Oct 20, 2020
74
8
Texas
In my '84 Oldsmobile Delta 88, I've been struggling with the blower motor since I got it. I've put 2 new ones in, neither worked, and the old one never worked either. I have confirmed with a voltmeter that everything upstream of it(resistor, relay, etc) is working properly, and the ground is good. I even went so far as to use jumper cables to directly connect the ground connector of the motor to the negative battery terminal. None of the 3 motors ever worked, and I'm at a loss for what else it could be. Any help would be appreciated.
Overkill the inspection and verification of the blower motor ground. That one thing could cause all of this. Don't just probe the connector. Unscrew it and check for corrosion underneath.

Also, I was just thinking, with the key in the on position slide the selector on the control panel to any one of the 3 a/c functions. If the compressor clicks to engage, go back and check the wires from the blower switch to the resistor.
 

TheBrisbyMouse

New member
Thread starter
May 1, 2021
5
3
Small update:
I took my voltmeter to the blower motor's positive electrical connector. The reading on the meter goes as follows:
Lowest: 5-7 volts
Second lowest: 12 volts
Second highest: 12 volts
Highest: Nothing
This seems to indicate that there's a problem with the "30 amp hot all the time" wire that goes to the relay, but shouldn't it still be able to work on the other 3 settings? The relay for the high setting also works, I can hear it clicking from inside the car. AC seems to work too, I can feel cool air coming out of the vents if it's on and I'm going fast enough to ram the air through.
 

GoodOldsGuy

Member
Oct 20, 2020
74
8
Texas
Small update:
I took my voltmeter to the blower motor's positive electrical connector. The reading on the meter goes as follows:
Lowest: 5-7 volts
Second lowest: 12 volts
Second highest: 12 volts
Highest: Nothing
This seems to indicate that there's a problem with the "30 amp hot all the time" wire that goes to the relay, but shouldn't it still be able to work on the other 3 settings? The relay for the high setting also works, I can hear it clicking from inside the car. AC seems to work too, I can feel cool air coming out of the vents if it's on and I'm going fast enough to ram the air through.
You have more than 1 problem.
I'm curious, what did you use for the ground reference when you checked the voltage on the blower wire? Was it the ground screw on the blower motor housing, or was it somewhere else? If you used a ground reference other than the ground screw on the housing, you are not verifying the motor housing is grounded. It should be checked at the blower motor housing. The blower motor gets its ground on the black wire that connects to the blower motor housing. It is circuit number 150 (a common ground circuit). The other end of the black ground wire meets up with the rest of 150 at the high blow relay in the 5 wire connector. It'll be the one with 2 black wires in one port. One goes to the blower ground, the other goes off to find the system ground. Check those wires and that connector. I'm sorry, I don't know where 150 connects to the system ground. Just make sure that ground is available at the relay and the blower motor housing. If that is good, make sure the purple wire (circuit number 65) has a good connection to the blower motor. You can test the blower motor by disconnecting the purple wire and running a jumper wire from the positive battery terminal directly to the blower motor power terminal (where the purple wire came off). Leave the ignition switch in the off position. That will bypass all the blower control circuitry and the blower motor should go to high blow immediately. Do not hold let the blower run like that for more than a second or 2. It'll use a lot of power and could overwhelm the jumper wire capacity and burn it up.
It's extremely unlikely that you have 3 bad blower motors, 2 of which are/were new. If the blower does not come with the jumper, there is either an open inside the motor (bad blower motor) OR the motor does have a ground to complete the circuit. I've never heard of 3 bad blower motors in a row, while it is possible, it's also possible to be struck by a meteor.
If the blower motor does come on with the jumper, the purple wire (#65) and its connections become the likely culprit. All of the blower motor voltage supply has to go through the high blow relay (no matter what the speed). The lower speeds voltage goes through the resistor, then to the relay to supply the purple wire. High speed blow happens when the control switch activates the relay and makes a direct connection from battery positive to the purple wire via the very heavy gauge red wire (circuit #2). Even if the relay clicks, that is not a guarantee that it is carrying voltage from the red to the purple. I'm surprised that you can hear the relay from inside the car, I can't hear mine, but I'm old. I can however hear my compressor clutch engage (click).
That's a long story, but I'm betting that the ground circuit is not viable at the blower motor for some reason. (Bad wire or bad connection at the relay) You can remove the blower and bench test it by using jumpers from the battery ground and positive directly to the blower motor.
I'll post a couple pictures of mine to help sort out what is what.
 

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GoodOldsGuy

Member
Oct 20, 2020
74
8
Texas
Small update:
I took my voltmeter to the blower motor's positive electrical connector. The reading on the meter goes as follows:
Lowest: 5-7 volts
Second lowest: 12 volts
Second highest: 12 volts
Highest: Nothing
This seems to indicate that there's a problem with the "30 amp hot all the time" wire that goes to the relay, but shouldn't it still be able to work on the other 3 settings? The relay for the high setting also works, I can hear it clicking from inside the car. AC seems to work too, I can feel cool air coming out of the vents if it's on and I'm going fast enough to ram the air through.
The first picture is the high blow relay (lower Shiney thing) and the blower resistor (the black thing on top with the white screw). The black blower ground wire connects to the relay connector at the same place the black circuit 150 system ground connects.
That big funky looking green wire in my pictures is how I repaired the always hot, main power supply from the engine harness. 43 years of being draped across the 403 and getting jerked around during untold numbers of engine repairs was more than the original red (10 gauge) wire could tolerate. I only had 10 gauge in green and I routed it above the engine around the back side. The second picture is of the engine harness where the always hot heavy red (in your case) wire connects. If the lower speeds work but no high, that heavy wire or the relay become highly suspect. But since none of your speed settings function, make sure the blower motor works independently of the rest of the system, if it does not, the problem is in the blower motor. If it does work with the 2 jumper wires, the high speed blower relay, or the connectors and wires on it are likely to be the culprit. It appears that your control panel switches and the wiring from it are functional, plus your resistor appears to be working normally, so again, I'd be looking for a bad ground connection (which could cause all of the problems you are experiencing).
The resistor has 3 stages of resistance. The most resistance (all 3 stages) is always on low blow. 1 click up on the panel switch bypasses one of the stages of resistance and more power goes to the blower, 2 clicks up bypasses 2 stages of resistance and even more power goes to the blower, the 3rd click up however activates the hi blow relay to supply full power directly to the blower because the resistor and the panel wiring cannot handle that much amperage.
I know that sounds overly complicated, but even way back then they were trying to reduce weight and wiring harness density. They knew the only condition that needed max amperage was max high blow, so instead of making the panel wiring and switches (plus the resistor) big and heavy enough to tolerate that much amperage, they designed a system that bypassed them for max high blow. That's why you can have lower speeds function but no high, or high speed function without the lower speeds, but if nothing works, it's likely to be a blower motor (just not 3 in a row) or a ground circuit failure.
So, I'd bench test one of the blower motors. If none of them work, go buy a lottery ticket and look out for meteors, and then get a blower motor that works. If one or more work, the problem is in the power supply, and in your case it sounds like the ground side of the supply and possibly the high amperage supply wire from the engine harness and/or hi blow relay. I wish I could touch and point at the stuff I'm talking about on your car, but describing it in words is the best I can do here.
It sounds like you have a good understanding of your multimeter and a grasp of DC power, so I'm confident that you got this.
I'm going on what I know for sure to be the case on a model that is a bit older than yours, but blower resistors and relays are still commonly used on brand new cars today. I can't imagine that computer modules were controlling those systems in your car (they didn't come along until much later), that's why I believe that your car has this sort of setup.
Keep me updated please, I'd like to know what you found out.
 

GoodOldsGuy

Member
Oct 20, 2020
74
8
Texas
Small update:
I took my voltmeter to the blower motor's positive electrical connector. The reading on the meter goes as follows:
Lowest: 5-7 volts
Second lowest: 12 volts
Second highest: 12 volts
Highest: Nothing
This seems to indicate that there's a problem with the "30 amp hot all the time" wire that goes to the relay, but shouldn't it still be able to work on the other 3 settings? The relay for the high setting also works, I can hear it clicking from inside the car. AC seems to work too, I can feel cool air coming out of the vents if it's on and I'm going fast enough to ram the air through.
You know, the thought just occurred to me, does the blower motor hum when you turn it in? Could it be that the fan cage that is attached to the blower motor is jammed on debris inside the housing? It's on straight, not loose, not able to rub on the inside, and not reaching so far down in the housing that it has bottomed out? I just want to make sure you have ruled out those sorts of things.
 

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