[Pepi]

Do you have continuity between 5 and 2 ever? It sounds as though you have a bad switch.

Just out of curiousity, see if you have continuity between 5 and 2 on DEF, HTR, VENT, B/L,and NORM.

Then check between 5 and 1 on MAX.
If it works this way, you have a 77 switch.

[Pepi]

Originally Posted by vidguy

OK. I don't know what you are going to think. but.. . no HI fan jumping the YELLOW and BROWN..

I took the connector off of the Rotary Switch and tried jumping Yellow and Brown and I can get all the speeds except HI. HI just sparks...

I tried it with the connector plugged onto the Rotary Switch. in MODE MAX AC, I opened the connector and Jumped YELLOW and BROWN and, again, I can get the OTHER Speeds so that's good, but no HI...

Check to see if you have continuity on the FAN switch between the terminals where the brown wire goes and where the orange wire goes. I forget if we did this already, but since the 77 diagram doesn't show the lever inside the fan switch, I am just wondering if it doesn't connect inside like I think it should.

[vidguy]

Pepi-
I Just checked this.
On the Rotary Switch: (both of mine, not the 75 but the 2 later controllers))
I have continuity between #5 - #2 on all positions except MAX AC (and OFF)

On the Fan Switch:
I have continuity between the ORANGE and BROWN terminals on HI on both of my FAN Switches..

In my previous test just before this I had the harness hooked up entirely.

I tested by jumping the ROTARY switch between #5 - #2 (YELLOW - BROWN) with the Rotary switch connector hooked up and the terminals exposed. MODE set to MAX AC
--All speeds on the Fan Switch worked EXCEPT HI .. HI Sparked...

I then tested it by only removing the ROTARY switch connector and Jumping #5 - #2 Mode switch set to MAX AC
--All speeds on the Fan Switch worked EXCEPT HI .. HI Sparked...

Something just isn't right. I must have overlooked something you guys suggested... I am going to check all of the terminals and connectors Ii have moved or altered tomorrow. The odd thing is not getting power to the BROWN wire from the Rotary Switch in MAX AC......???

[LPete]

James, please check the continuity between pin 5 and pin 1 on max a/c. If you have continuity you need a different control -- a '78, most likely.

[Pepi]

Originally Posted by LPete

James, please check the continuity between pin 5 and pin 1 on max a/c. If you have continuity you need a different control -- a '78, most likely.

Yes, please check that scenario. If you have continuity between 5 and 1 in MAX A/C only, you have a 77 control head. If that is the case, you will need a 78 Control head OR you could add a wire going from pin1 to your your orange wire. That will get you power to your fan on HI. But we need to figure out why it just sparked when you jumpered power between yellow and brown and got sparks on HI.

[vidguy]

OK I'll try that one tonight. I dont have the control or meter in my car today.
THANKS!

[vidguy]

I do have continuity between #5 and #1. On MAX A/C.
I worked late tonight and didnt have a chance to hook anything up. I will try hooking the harnesses back up tomorrow and testing the suggestions you have both made.

It sounds like you guys are correct that there is a difference in the rotary switches on 77's and 78's. That just seemed so unlikely as all of the controls and switches of those years look identical.

But after taking one apart I can see how they can put a different "switch plate" inside the rotary switch.. I guess I was unlucky in that neither of the controllers I bought in preparation for this swap are not 78's! Nor was I concerned with that.

Thank you very much,

[Pepi]

Originally Posted by vidguy

I do have continuity between #5 and #1. On MAX A/C.
I worked late tonight and didnt have a chance to hook anything up. I will try hooking the harnesses back up tomorrow and testing the suggestions you have both made.

It sounds like you guys are correct that there is a difference in the rotary switches on 77's and 78's. That just seemed so unlikely as all of the controls and switches of those years look identical.

But after taking one apart I can see how they can put a different "switch plate" inside the rotary switch.. I guess I was unlucky in that neither of the controllers I bought in preparation for this swap are not 78's! Nor was I concerned with that.

Thank you very much,

Well, at least we are making some progress . We've identified some of the problem.

Just to recap now, your fan does work in all low speeds, just not HI, and nothing in MAX A/C. Right?

[vidguy]

Yes. exactly. I got home very late tonight.. Ill check the 5-1 jump in the AM.. I am leaving on a business trip on Saturday evening for 5 days... Just so you guys dont think I left you hanging..
Thanks so much,

[Pepi]

So if you go to NORM position the HI doesn't work? Did you ever have HI working with the 5 pin relay? I know we had HI working at one point, but I am not sure if that was with the 4 pin relay. Like Lee said, maybe there is a diode in the relay trigger, so the GRAY/BLACK and BLACK may have to be switched, or maybe a bad relay, or relay must be secured to firewall?.

[vidguy]

Well, I tried a number of the previous test again and I never heard the Relay clicking.. I tried jumping GREY and RED at the relay as before.. no go..
I took the relay apart..
Looks like there is a Diode and that it melted... You guys were right.

What do you guys think? Anything I can do to rig this up?
Pepi, I never got HI in any position since putting the 5 position relay in..
in MAX AC I still do not get any response at any speed. That is a Rotary Switch issue I think as you guys have been saying...

In my testing today and the other evening I noted that in HI FAN position My ORANGE wire gets really HOT coming off the FAN switch. ( said it was the BROWN before and I may have been mistaken.)
Could this be why?

I dont know when I burned it up...
Im going to order another one.. a different part number if I can, but with 5 positions..
I'll try jumping Rotary Switch #1 to the ORANGE wire which connects to the GREY wire to the Relay, once I get a new relay...As you suggested Pepi.
Thank You,

[LPete]

If the diode is shorted (and I'm betting it is) that explains the wire getting hot.

Either the diode was already damaged, or your wires are hooked up backward at the relay. If the wires to the coil are switched it will instantly ruin the diode when power's applied. Actually, if the diode is shorted (measure the resistance across the two coil terminals -- if it's close to zero measured both ways it is shorted) you could cut a diode lead and the relay will probably work.

[vidguy]

Lee-
Thanks for the info! Im in Boston right now until Tursday night. I'll order a new relay online while Im gone and try yoiur suggestion oifcutting the lead.. I will also look at the wiring diagram and see if I can match up the terminal #'s on the relay to the wiring diagram to verify the grey wire is in the right place.

[vidguy]

SUCCESS.
I received a 1978 Blower Control Switch (Rotary) from Rockauto.com About $23.00 shipped.
It was different then the other two I have been testing with.. It had No terminal #1. I searched specifically for a 1978 and when I got it I was relieved that it was different.

I also ordered and received three 5 terminal relays at the same time. They had a closeout and I got them for about $4.00 each. so I bought three, in case I blew one up again.

I first attached the control head using the harness that had the double yellow on terminal #5 and no double brown/white coming off terminal #2.

All I had was low on all speeds.......

I swapped that for the harness that had the double BROWN/WHITE on terminal #2 and the single YELLOW power connector on terminal #5 and BINGO! I have total fan speed control on all mode settings..

Specifically here is how it is working.
On off there is NO LOW speed.
ON MAX A/C it does NOT override the Fan Switch and go to full HIGH. But I can control it to run on all 4 speeds in MAX A/C.

On all other Mode Positions if the Fan Speed Switch is on "LO" it runs LOW. And all of the other 3 speeds work as expected.

I want to thank everyone that helped me out. Especially Pepi and Lee. This was not a critical thing like some problems. It was kinda a goofy thing but it was my thing.. Still, you folks were there to help me out like i had busted my oil pan open in the middle of the desert!
If you guys are ever in California let me know. So now onto the dash install.

[Pepi]

Glad you got it working, I was just trying to look through the wiring diagrams, and unsure why the one harness didn't work, because double yellow should have been for the '78. But WHO CARES IT WORKS!!!

Let us know if you have any issues with the dash install.

[LPete]

Originally Posted by Pepi

But WHO CARES IT WORKS!!!

Wow, no kidding -- I'm not sure it's working exactly like it's supposed to, but it's working like millions of other cars on the road do. Glad you got it!

[vidguy]

I just spent a few hours cleaning up the wiring under the hood. Mounted the relay and resistor, new terminals for the ground and the red alt wire..

I too was curious about the harness with the 2 yellows and how it worked..I wonder if it would have worked with the new RELAY (one that's not burnt out) and the old Rotary switch.. I still dont know at what point in my previous testing that I burnt that Diode in the relay.
.. I'll try the other harness again.. I do have 2 part numbers of these new Relay with 5 terminals. Maybe I'll try that harness again with the old rotary switch and see.. I agree that it isn't working as we thought it would, but... It's close enough for Rock and Roll.
Thanks again.

[vidguy]

It's been cold here... Just wanted to drop into this section and give a bucket load of thanks to you guys that spent considerable time helping me with this issue back in September last year..I have a warm ride... Every time I hit the Fan Switch I thank you guys.
(is that sappy?)
And in the process, this thread I believe became the ultimate internet resource for climate control information for Second Generation F-Body cars. I find myself referring people to it once a month or so.
Might almost deserve to be a STICKY.

[Pepi]

Glad to hear!
I am waiting a little longer to get mine out, normally easter weekend. Need all that salt on the road washed away Then I get to make sure my AC works!