64-65 Rear Blower questions - lingering issues

[Dan B.]

I've been working on getting my rear blower to operate more as advertised. Some history, I completely rebuilt the entire unit and motor, have replaced the pull cable, and the wiring is all new. It wants to operate as it should but first problem was even with a new cable well oiled it is was still difficult to actuate. You needed 2 hands (one on the pull, and one on the housing to prevent pulling too hard and damaging the attaching housing. This in spite of smooth cable and switch operation when hand actuated individually. I was able to fix that part of the problem by removing and diassembling the original swich and reworking the indents to be less pronounced and thereby reducing operating effort required. That worked well, and now the cable will move the switch with one hand.

The second issue is the 3 speeds. With the key on and engine off, You can clearly hear the front blower at all of it's speeds operating. The rear however does not produce similar results even if you take the cable out of the equaiton. If cold, it will will start out OK at the slow speed and then once the resistor warms up after a few seconds it will come to a stop by itself. Fast speed is fine when the resistor is bypassed.

So here are some questions for the experts on both repair and what correct operations should be:

1. The original INDAK resistor does not appear damaged, and I checked it for continuity (good) and then with my OHM meter and it does show resistance to both circuits (though I have not found any specs to compare it to). Is it possible due to age that it has simply built up too much resistance once it heats up to continue working?

I know replacements are available, just trying to understand the mechanics here and if possible save the original.

2. Those who have experience with 64-65 blower operation, what would you say the effort required to actuate the motor via the cable pull is on the best possible operating system (one that has been thoroughly gone through) ?? One handed easy pull, or two hands ect???

I've read all the posts I can find and some tech articles as well, but could never determine any deffinative standard for factory new type operation. What type of effort would a judge accept and assign full points for as an example?

Thanks for your input, Dan

Here are some photo's, of the exploded view of the switch and rebuild I did

[Ken R.]

Re: 64-65 Rear Blower questions - lingering issues

On my 65 that I bought in 65, I always had trouble pulling the handle knob. I just learned to use the 2 hand method; 1 on the knob, the other on the support bracket. My bracket actually had an "offset" in it after many years. I just took it to be the nature of the beast.

[Dan B.]

Re: 64-65 Rear Blower questions - lingering issues

Ken that's very helpfull knowledge. I actually de tuned my switch when I was rebuilding it which made a huge difference in the effort required to operate now. Thanks for your reply!

[Don H.]

Re: 64-65 Rear Blower questions - lingering issues

Dan, I agree with Ken, all three I have owned pulled very hard. Another thing to remember (probably not affecting your problem) is that the power to the rear vent motor comes through the heater/defroster blower motor switch. When you turn the heater switch to low (or any speed) the power is cut off to the rear motor. Don H.

[Dan B.]

Re: 64-65 Rear Blower questions - lingering issues

Don, thanks for your reply. Confirms what I was thinking based on my experience working with it thus far.

Hopefully, someone will chime in with some insight into the resistor question. I went ahead and ordered a replacement anyway (got an NOS original) and can always use it to get the new resistance values. It will be interesting to compare the readings to the used one.

[Richard G.]

Re: 64-65 Rear Blower questions - lingering issues

How about bypassing the switch and running it on the different speeds with jumpers?
This could prove if the heating is in the resister or in the switch.
It is possible when you modified the switch for easier movement you may have changed the resistance.
You didn't mention if the "starts and slows till it stops" was also there before the switch mods.
Try hooking up a volt meter to the motor legs. You should be able to see the resistance change in the form of a voltage drop.
As the motor slows is the voltage dropping?
Rick

[Dan B.]

Re: 64-65 Rear Blower questions - lingering issues

Rick, the switch (on the blower) is basically just an on/off switch that distributes full power which it is doing. My mod just made it easier for the cable to move it. The resistor (separate) gets VERY HOT which confirms it is receiving power when the switch is in the low and med setting, and to awswer your question, YES the motor speed issue (running slower) existed previously. I have to recharge the battery now before I can do any further tests with the multi meter. I will take your suggestion and double check the switch just to be sure it is putting out full voltage in all positions. I am still leaning towards the resistor since when removed I get full speed. I'm on a mission and will eventually find the issue. By nature I am not a parts replacer, I like to thoroughly troubleshoot electrical problems. Compared to working on the newer cars (which I do) these old Vettes are a pleasure.

[Ray K.]

Re: 64-65 Rear Blower questions - lingering issues

Dan - all

The blower motor control on my '65 coupe, although firm, is easily operated with one hand and has always been that way.

Ray

[Dan B.]

Re: 64-65 Rear Blower questions - lingering issues

Thanks Ray, I think you are now the envy of most of the rest of us who deal with a "heavy pull".

[Dan B.]

Re: 64-65 Rear Blower questions - lingering issues

After more troubleshooting with the multimeter, I am getting a slow speed and full high speed only now. I am expecting to still see 3 speeds as advertised. Checked the resistor (wired but not attached to the housing) see photo and it is red hot on the large side. So, the problem now is I am missing the middle speed. Going to replace that resistor anyway for peace of mind. So, can some of you who have been following the thread confirm you are actually getting 3 differing speeds from your rear blower. Again my thought is it should operate similarly to the front right? What is confusing is the switch cam only has 3 positions, with the right being off, middle I get slow fan speed, and left is full blast (see photo 4), where is the third speed supposed to be?

[David Z.]

Re: 64-65 Rear Blower questions - lingering issues

Dan,
I sent you an article via email with a possible fix for the three speed issue.
Let us know if that works out. If it does, we'll post up that fix.
Dave Z

[Dan B.]

Re: 64-65 Rear Blower questions - lingering issues

Hi Dave,

First many thanks for joining this thread. The paper that you did years back on the Coupe rear blower is by far the best I've seen on the subject with it's pictures and descriptions. All of us who are working on them owe you a debt of gratitude for your effort and contribution, so let me acknowledge that up front (again).

I looked at the page you sent (from the 65 shop manual) and I had already seen that as part of your original paper (pages 12-14), was there something in addition to that you meant to send?

To recap now, I have a nice smooth and much better operating cable / switch pull than before. I only have slow and fast speeds though. The original INDAK resistor tests good for continuity and as you can see from my photos above offers a resistance value on each circuit. When its installed in the car the heavy coiled side glows bright orange when the fan is running at slow speed which is disturbing and I am waiting for the replacement to arrive, but don't know if it will make a difference on the missing middle speed.

If nothing else I have at least that to try. New wiring harness also looks correct (not per original GM schematic error).

Regards, Dan

[David Z.]

Re: 64-65 Rear Blower questions - lingering issues

Dan

Thanks for the kind words.
I guess the one-page article did not come through with my email.
Hopefully it will show up here.
Dave Z

[Dan B.]

Re: 64-65 Rear Blower questions - lingering issues

I checked that diagram and confirmed the new Lectric Limited harness is manufactured to the original factory blueprints and NOT the wiring schematic meaning it should match an original harness and is correct as delivered. I am also still getting 2 speeds currently. I think it's an electrical problem, but not associated with the wiring harness.

More testing with the multi meter is needed, stay tuned. I am making progress!

[Dan B.]

Problem solved !

The multi meter comes through again!!

Having a good multi meter and knowing how to use it is invaluable in troubleshooting problems in these cars.

A few general comments about things I found out. First, absolutely there should be 3 running speeds as advertised. Second the new wiring harnesses have already solved the wiring schematic error, so that is no longer a factor. You can greatly reduce the cable pull effort by doing some rework on the switch besides just cleaning and reassembly.

So, the problem here turned out to be a resistant resistor. I had checked it for continuity and also for resistance on the bench and it appeared OK and looked good for a 50+ year old part at first glance. My first tell tale was it glowed bright red when energized (they are supposed to get hot, but not red hot) in the car and yielded only slow speed. Hmmmmm, decided to confirm power was present in all 3 positions on the switch and it was. Power was also present at the resistor on both circuits low and medium, but the fan would only spin at low speed when it should have been delivering medium speed at that setting. A voltage test in the car revealed excessive resistance in the LOW position where there was voltage, but it was insufficient to spin turn the blower (only 1.8 volts). In the medium position, I was only getting 3.5 volts which made the motor appear to operate as though it was running at it's normal slow speed. Full speed was never an issue since the resistor is essentially bypassed.

Hope this is helpfull to others who may have either front or rear fan speed operational issues. The principle is the same and both front and rear motors should operate at similar speeds. An easy way to check your system: with the engine off and key on, listen to the 3 speeds in the front motor and then see if your rear blower sounds the same, it should. Thanks again to all who offered assistance early on. Dan