C5 blower motor issue

[Rob M.]

I have a 1999 Corvette (driven now app. 440.000 km) with the standard manual temperature control unit featuring a 0 till 5 blower speed switch. Currently, the blower only works when set to 5, while settings 1 till 4 have stopped functioning over the past week. The motor was squeaking occasionally before this issue began, but the noise often stopped when the switch was adjusted to a higher or lower setting.

Questions:

1) since the blower motor still runs on full speed I think it is still ok (although it might have bearing issues), do you agree?

2) I suspect the motor control unit or the switch, what is likely not working?

3) I guess I need to oil the motor a bit to prevent the squeaking, do you agree?

regards,
Rob.

[Edward J.]

Rob,I think you problem lays with the blower resistor , or if it’s electronic Circuit board for blower. The blower generally works on high speed with relay. The other 4 speeds use a resistor to cut the speeds.

[Gary B.]

Rob,

C2 blower motors may be a bit different, but I’ve tinkered with four C2 blower motors and several would not run at the lowest of their 3 speeds. I tested them with a regulated power supply, so the dash switch and the speed resistor were not involved. The 3 speeds are obtained by powering at 3 voltages. I’m sure the problem at the lowest speed is that the motor doesn’t have sufficient power to overcome the frictional forces caused by insufficient oil at the Oilite bushing after 59 years of use or disuse.

In your case it sounds like it’s not just a lubrication issue, but lubricating might fix the squeaking problem.

Gary

[Rob M.]

Well, after diagnose I encountered the following situation:

1) blower motor rotates (a little heavy when rotated manually) but draws a lot of current (> 2.5A above 4 volt causing my lab power supply to limit the current)

2) resistors module looks like it had its best time, it might be destroyed by the access of current drawn by the blower motor...

So I ordered both yesterday to be replaced...

[Gary B.]

Rob,

These are the amp readings at the three fan speeds from two ‘66 blower motors I have:

Original blower motor
11.0v -> 5.8 amps
5.9v -> 3.8 amps
2.5v -> 2.2 amps

Spare blower motor
11.0v -> 2.8 amps
5.9v -> 2.4 amps
2.5v -> 2.1 amps

If my original blower motor ever acts up, I plan to go thru the oiling process that Joe Randolph described that requires drilling a hole to allow oiling of the Oilite bushing.

Gary

[Rob M.]

So the high current draw might be expected (although I will replace the motor nevertheless but I will keep the orginal as a spare for now)...

Thanks for this feedback, very usefull during troubleshooting...

PS where do I find that hole drilling procedure, is it in the Restorer and if so in which edition?

[Gary B.]

Rob,

Contact Joe Randolph (37610) for the hole drilling technique. It might also be described in the archives, but I don’t know for certain.

Gary

[Rob M.]

I have been able to fix the issue. The conclusion the fan motor was sort of shot drawing too much current which melted the resistors for the 1 till 4 setting.

I ordered both a new resistor circuit and a new fan. The resistor circuit arrived first but when I attached it and switched to a 1 till 4 setting it soon started to smell like burned plastics. I stopped using the 1 till 4 settings again (only used 5) and waited for the new blower motor to arrive.

Once the new blower motor arrived I swap it in the car and all worked as intended (no more smelly plastic odors and properly working 1 - 4 fan speed).