1960s My 68 climate control blower motor questions

[Steve W]

In my 68 Coupe deVille, the blower motor is acting strangely.
When I slide the selector lever to Low or High...nothing happens.
Then I move it all the way over to Ice...and the blower starts blowing air at the windshield...and then I can move it back to Low or High, and it stays working and blowing out of the appropriate vents, until I move the selector to the off position. If I turn it right back on again, it functions as it should. But if it's off for awhile, I have to slide it all the way to ICE, then back to low or high.
It doesn't matter what the temp dial is set at.
 
Also. I suspect that the blower isn't moving as much air as it should, but I really don't know because I've never been in another 68 with a working climate control system. The high setting moves a bit of air, not great, but it's coming out of the vents. At low setting...it's barely moving air through the center vent...and next to nothing at the far left or right vents.

If the blower is blowing air, and changing speeds somewhat, does that mean the blower motor is OK? Or do they weaken over time? Does the resistor or relay help determine the volume of air the blower moves...or is it a matter of "they either work or they don't"?

And if anyone has a working system in their 68...does the air come out at a decent speed, or are they kind of weak?

Thanks in advance,

[Julien Abrahams]

What you are experiencing is probably vacuum leaks somewhere. The whole system depends on vacuum and this means that all hoses, vacuum valves (that control the air flow doors) all need to be air tight, just like the rotary valve. Not entirely sure if the '68 system is much different than my '67 system.
You could check if the blower motor is functioning as it should by measuring the amps it draws.
A simple test would be to set the dial to max heat and putting the lever on Ice. The blower motor should run at full speed and the system should give maximum heat regardless of the temperature in the car.

Connect for example a multimeter in line with the motor to see how many amps it draws. Fro, memory I believe it draws about10 amps at full speed. Then put the lever on Auto and turn the dial to its lowest setting. The motor should go to from full speed (from the Ice setting) to low, to mid and then to high as the temperature in the car is higher than the setting on the dial, so it will kick in the AC to get the temperature dowon.  The different speeds of the motor will be indicated by the different amps it draws.

That being said, I think it depends on what you compare it with. If I compare the amount of air coming out of mainly the center vent or the vents in the foot well when the system is giving me full heat in winter, it gives much more air flow then my '79 Opel Kadett or my '69 Austin Healey. However, when compared to a modern car, the air flow is much less.

[TJ Hopland]

There were often slight changes year to year or at least every couple years so you really need to get the manuals for your specific year to get specific troubleshooting.  When it comes to the blower speed generally what is different about ICE/Defrost is that going to that mode bypasses the coolant temp sensor.  The temp sensor is there to delay the blower coming onto higher speeds till the coolant is warm enough to actually make some heat.  Without seeing the full diagram I can't explain if/why it stays working or why if it was asking for cooling the blower doesn't come on but its the area I would start with looking at the manual. 

If a 68 is like the 70's system the sort of main working element of the system is a single vacuum servo that is electrically controlled.  The one motion operates a door as well as the blower speed and a vacuum control valve distributor thing that then operates other doors. It just controls the speed of the blower IF other control aspects decide it should be in auto variable speed mode. Thats where modes like ICE bypass the variable speed and coolant switch.

So you could have many small issues like maybe one or more of the control doors in the ducts are not working.  Maybe the middle door in the chain is partially closed when its supposed to be open and that is slowing down the flow?  If the airflow is like later cars all the blower air flows through the evaporator (the AC radiator thing) and over time the fins can become clogged with general grime and debris blocking the flow.  If there is or was a freon leak the oil or a stop leak product the oil that comes out at the leak will attract dirt and make it stick again blocking the air flow.

Another big issue as time goes on is the blower motors and fan blades don't tend to be exact replacements.  The manufactures as time went on seemed to decide one size kinda fits some was more profitable than an exact fit version that only fits a couple models.  Very slight differences in the fan blade size and shape can make a huge difference in the performance. Even where the blade is placed on the shaft so how far it engages in the housing can make a big difference.   

 

[Jeff Rosansky CLC #28373]

These are year specific and I don't know about your year for sure.
But this is what I'm thinking;
The system turns on 3 ways- when cold the engine temp switch. When hot the in car temp switch, and when in defrost regardless of the temp.
If this happens when the car is 1st started then you turn it to Ice and it works. Then the engine warms up and the engine temp switch takes over and the system works normally.  Sounds to me like your in- car sensor isn't working. Try leaving it in auto for a few minutes to confirm this. If so then as soon as the engine warms up it will come on automatically just like it does in the wi ter.
I have found Cadillac Tim's books very helpful. You can Google him. Books are about $45 or so and we'll worth it.

[cadillacmike68]

It's a vacuum leak.

You might want to get Cadillac Tim's booklet.

[Steve W]

I just got off the phone with Cadillac Tim. Hellova nice guy! I ordered the book for my car! Thanks for the referral, guys!