Need help in testing blower motor

[TrickySF]

Any assistance will be appreciated. How can I properly test each blower speed with 12v power coming directly from the car battery on a 74 Carrera. I want to avoid the car wiring.
I have only one speed on the fan coming from the middle setting of the climate control panel slide. No fan speed on the low setting and no fan speed on the high setting.
I am trying to find the problem by elimination. The climate control panel seems to be in good condition. When out of the car, the terminals for all three speeds were cleaned and the power copper slide plate was also cleaned and brightened. All lights work and the fan light works when the slide is moved to the first low setting and all other speed settings.
If the climate control panel is working properly and the blower can be tested not utilizing the original wiring, then it would appear that the problem is in the wiring between the two. Many thanks for any advice. Stay well.

[timmy2]

There are speed limiting resistors under the cover that may have failed.
Undo the screws and take a look.

[TrickySF]

Thanks Timmy2 for the reply. I have a new Classic Retrofit A/C blower that I just plugged in and the new blower also has but one speed in the same position of the fan slide (medium, no low and no high), so it is not the blower. That leaves the control panel slide or the wiring/plug between the control panel and the blower. I will remove the control panel again (hate to do it) and check the continuity between the three fan positions and the plug under the dash and/or check voltage coming from each prong of the four prong plug in the frunk that plugs into the blower-with the fan slide in the proper fan speed positions. Any thoughts?

[timmy2]

Black wire wire in the square plug is power, there is a white, a white/yellow and a white/green that are the fan speed return paths to the speed position sliders.
Check for continuity for each of the 3 speed control wires to the sliders is all you can really do.
The black power wire is constant.

[harv666]

Originally Posted by TrickySF

Thanks Timmy2 for the reply. I have a new Classic Retrofit A/C blower that I just plugged in and the new blower also has but one speed in the same position of the fan slide (medium, no low and no high), so it is not the blower. That leaves the control panel slide or the wiring/plug between the control panel and the blower. I will remove the control panel again (hate to do it) and check the continuity between the three fan positions and the plug under the dash and/or check voltage coming from each prong of the four prong plug in the frunk that plugs into the blower-with the fan slide in the proper fan speed positions. Any thoughts?

Is the retro ac supposed to have multple fan speeds from the switch, I've just ordered mine and figuring out if I need to replace the heater control because mine is doing the same thing.

[TrickySF]

Yes, the new Classic Retrofit a/c blower has three speeds. I will be testing the upper fan slider positions to plug for continuity today and will let you know if that is the problem. If it is not the problem then it would appear that it is the either the plug (bad contact) and/or the plug receptacle under the dash or the wiring from the plug to the blower in the frunk. I will take one at a time until I find the problem.

[TrickySF]

I am baffled. I removed the climate control "slide" panel from the car and checked each slide position (low, medium and high) positions individually from the ground wire to the plug pins and all wires and plug pins have continuity. After checking the above, I hooked up the panel under the dash with the plug plugged in and the ground attached. When operated on the fan settings, the fan light comes on, but only one speed still comes on. After testing several times I got no speeds-the one speed just quit.
I removed the blower and tested each of the plug pins directly from the battery. That test revealed that all three speeds work perfectly from direct power. So, the panel slides make contact and have continuity to the plug and the blower speeds do work but not together. That leaves the wiring from the 6 prong plug under the dash and the 4 wire plug that operates the blower. The wiring diagram shows every wire and I have confirmed the wire colors and they are accurate. I will now try to figure out how to go around the original plug under the dash and the 4-hole plug to the blower. Not sure what else to try.

[timmy2]

Spread the pins on the male plug with a razor or exacto blade.
May be poor contact in the 6 pin plug.

[TrickySF]

Thanks Timmy2. I cleaned each pin with a small emery board yesterday before all the testing that was made. All pins are very bright.
Anyone know if the wire placement in the plug as shown in the photo is correct:


The wire pattern is:
Black-upper left for power
White/yellow upper right for medium speed
Green/white-lower left for low speed
White-lower right for high speed

It appears to me that the back of the plug which snaps off has been opened in the past from the pry marks on each side of it. Just wondering if the pins were removed at one time and then replaced properly. Checking everything that I can for accuracy.

Thanks everyone for the assistance. Much appreciated. If I had any hair I would tear it out on this one.