Carl79

I have checked the fuse box (Fuse ok). I have replaced the blower switch, still no power. In my mind I only have three other possibilities.
One is the high power blower relay(I checked for continutity and received current from the upper posts but not from the lower) (Could this be the problem) Two would be a bad blower motor. or three a bad ground. I can't locate the grounds. I could use help. Can anybody think of other possibilities that I am over looking? Thanks Guys,
Carl.....79 Corvette L82

...Roger...

No power in all speeds ? Did you check the fuse using a test light and check for power on both sides of the fuse and where the fuse plugs into the box ? Use the test light and check the purple wire for power with the switch in all position. Also check for power on the red wire at the high speed blower relay.

SIXFOOTER

I agree with Roger
Here is a decent drawing

The ground thing is a serious one to check out. Many times when a starter is swapped out, the groung cable ends up connected to the + terminal on the starter. What it does is ties the blower and WW motor ground to +, meaning it won't work. Run down the ground wire from the Hi Blow relay, it should tie in the blower and the engine and WW motor and the blower motor

Carl79

Thanks all !!!!

I'll get to work immediately with your suggestions
I'll keep you abreast of my headway !!!
Carl.

Carl79

Well, I was able to jump the terminals at the high speed relay and got the blower working !!! So... I ordered a new relay and will put it in today. Not sure why it caused all the speeds to not work (possible ground) but its a start. I'll let you know when I get it working and all buttoned up !!!

Carl79

Ok, I'm confused. I have an early 79 The high speed blower relay is three upper two lower. The three upper are arranged in a T style meaning two up and one below. When I jump the two uppers on the upper plug the blower comes on. I get no power indicators from the third wire (Below) on the upper plug and no electric indication out of the lower plug at all. I thought replacing the H/S relay was the answer...but NO !!! Could the low speed resistors stop the blower motor if switch is on high speed?....More help needed !!!
Thanks
Carl

...Roger...

No.....the red should be hot all the time
the blue should be warm to hot (resistors) when the key is on if brown at the resistors is hot if the 25 amp AC fuse is not blown.
the purple is the wire that goes to the blower if its hot the blower will be running
lower wires in plug
the orange is hot when the fan is on high
the black is a ground-make sure it is in fact grounded

Probe some wires and let us know where you have power

Carl79

Ok... The only way power is indicated is when I jump the red and blue wires at the relay, and the blower starts. I get no positive electric reading on any other wire, All of these tests were conducted with the switch in the high position. To me this means the 25 amp fuse is ok (tested it, looked at it , it is ok) I think it also indicates a good ground, or the blower wouldn't start. I checked all wires with a light tester but could not get a single wire to light even using several different frame grounds??? The only way I get the light on is when I connect red and blue. No other wires indicate power. Thank you Carl

TimAT

Start at the top of the diagram and work your way down, following 1 lead at a time. The one marked 2.0 brn should be hot with the key on at the blower resistor in the fan case. Then with the fan switch on low the dk blu 3.0 should have power all the time, With the mode switch in Normal A/C, Vent Heat and Defrost, Medium speed should be the same with the next 1.0 tan, then right on up the ladder.
Could be the mode switch on the control head if you have no power to the resistors, and that will also disable the high since the trigger to the high blow relay has to have a source thru the control head.

falconview

Almost sounds like you have a problem at the resistor, a comon problem in GM's

...Roger...

Carl lets do this one step at a time.
Turn the ign key to on.
Set blower switch to low
Go out to the engine compartment and pull the 4 wire plug off the resistor board.
It should have a dark brown, light blue,dark blue and a tan in the connector.
Probe the dark brown wire it has to have 12 volts on it.
If it doesn't then your problems are inside the car .
The 25 amp AC fuse is blown or its not making good contact in the 2 contacts it is plugged in to in the fuse box.
Or it could be as TimAT said a problem in the control head or just unplugged.
Let us know if the dark brown is hot.

falconview

There's a fusable link which I believe goes to the starter which is where your jumping red to blue is hot at all times thats why your motor starts working, try jumping 12v to your brown and yellow with the plug disconected from the the resistor, if you get fan action its your resistor...note when you jump to brown and yellow you will get full fan but that will let you know if its the resistor,

Carl79

Once again thanks to everyone .....I'll try first thing in the am...Don't worry , I'll let you know....Thanks again
Carl

...Roger...

What did you find,is the brown hot ?

Carl79

Sorry guys. Now I'm having trouble with the forum page. It wouldn't let me log in.

No, the brown is not hot I cannot get any power indications from the brown wire. I am in the process of checking the fuse box just in case of a bad connection at the fuse. I will also try to get power indications from both sides of the a/c fuse. You talked about the control head and I'm not sure where you mean. I also don't know where this linked fuse line from the starter is. I haven't been able to find that.

Once again I really appreciate everyones help. Thanks again.
I think I know what your going to tell me. I need to get power to that brown wire, right? I'll get to work on that.
Thanks again
Carl

...Roger...

On the fused link at the starter--you have already proved that is OK by when you jumpered the red to the blue--the red was the source of the power ---fused link is OK

The control head is the AC control in the console including the fan switch.
Pull the right side carpet off the console exposing the head control and check to see the fan switch connector hasnt just fallen off.
At this point you can diagnose this at the control head. You can check the brown at this point.
(it will be much easier on your back than trying to get to the fuse box)

edit-- The control head is where you will find the "yellow" that falconview spoke of, he was mistaken when he said it would be at the resistor board in the engine compartment.

Carl79

Gentlemen !!!!

It took three days and god knows how many hours but I got it working. I followed your instructions and cleaned the plug and contacts going into the head unit. I Then tried to to the same at the fuse box. Lots of luck upside down and all. I'm not as young as I was when I bought the car 30 yrs ago!. I then changed the fuse. I was using a cheap fuse the kind that you buy at Dollar General, you know the ones, 20 fuses for 75cents !!!!. I pulled that fuse out and put in a more expensive type fuse. After doing all three things I turned the key and yippie the blower worked. Now I gotta button every thing up with out destroying the other wires. I would have been in over my head if it was not for all your help. I can't tell you how much I appreciate it. I bet I saved 400.00 dollars doing it myself. Thanks again. I'll write back when I get it all closed up.
Carl
Ps... I love this forum !!!!

trjohn57

It's nice to find these sites. I've been playing with my heater to get it to work and sure enough my fuse was burnt. It only runs on a very low speed, but I will geterdone sooner or later.

coupe64

....... I think I posted before I had this problem with mine Its the small ground wire that attaches to the starter bolt under the car I fixed it before and the heater fan switch works fine ! Tonight I went to put my blower on and it wasn't working again ! I suspect the ground wire broke ! Going under the car tomorrow . I think the wire was too short gonna make it longer !!! This ground controls the heater blower switch !!!