82 blower fan pops 25amp A/C fuse
 

Brought an 82 home a few weeks ago as a hobby project and have started to go through some of the issues that exist. This particular one is being a pain, as most electrical issues are for me.
I don't remember the exact order of all my troubleshooting, but suffice to say many parts have been replaced now.
I first started out with no blower air at all. Don't really want to be driving around without at least the option for heated air if needed so decided to tackle this issue.
Removed the center console and the blower switch. Used the helpful video that Willcox Corvette made and found the switch to be bad. A new switch was installed but no joy.
Thus far I have methodically been going through the system and replacing the bad parts as I have found them.. sadly though, it appears nearly all the parts in this one system are dead or near it.
The other systems of the electricals in the whole car so far are doing okay (except power door locks).
The next item was the blower motor relay. From my previous searches and reading I figured if I wasn't getting low speed it would be this component.
Installed a new relay and was getting 12V at the terminal plug of the blower motor. Progress, or so I thought.
However, blower motor not working still. Removed it and jumped it to the battery directly and it would spin up but when connected to the system......nothing.
Fine, new blower motor was >$20 to replace and that was done. Now I have low and medium speeds but every time I put it into high speed, the 25amp A/C breaker blows.
Pulled out the low speed resistor from the A/C box today as well and cleaned the contacts, just because it was so easy to take out and do. Also wanted to make sure the coils were okay and they are.
The mystery remains, why does the high speed fan selection blow the 25amp A/C fuse no matter what mode the system selector is in?

Thank you.

electrical gremlins in these old cars can drive you batchit crazy.. I chased down several after putting body back on frame 10 yrs ago. But many times its poor grounds.. make sure your blower is well grounded and your engine is well grounded to chassis. .. does it blow fuse instantly or does it take a little time? if it isn't instant, feel the blower motor to see if its heating up. also make sure the wheel is not rubbing on housing ..someone else may chime in with another idea. good luck..

See if fuse pops when blower is not hooked up. See if a lighter fuse blows with blower unhooked.

Yes, the fuse blows instantly. I'll use a new 8 guage wire for a test ground to eliminate that half of the circuit later today and report back.

Hadn't thought of or tried that yet, I'll give it a try today after work.

Disconnected the blower motor positive line and turned the blower to high with the controls set to the far right for Heat/Defrost and promptly popped the breaker.
Pulled the console out again and now waiting for the new A/C control switch to arrive. Think I'll replace the breaker and try the high speed again with the A/C control out of the loop, the high speed should work alone
if I am reading the Willcox schematic correctly.

Nope: did not run on high with the A/C panel unplugged. So much for that theory. Didn't blow the breaker either, so there is that.

Well, I can only surmise that I have a bad wire grounding out in the system. Installed a new A/C controller switch and the 25amp A/C breaker still blows in the high setting only. I noticed that the volt meter guage needle swept very quickly over to the right before I heard the audible snap of the break blowing. Not sure what that means, but wanted to post it in case it does.
I unplugged both leads from the blower fan and the breaker does not blow at all... Going to try another experiment. Install a brand new ground from the blower motor to the engine block. See what happens to the fuse then.
I broke down and ordered a Power Probe 4 to assist with the troubleshooting process because my intent is to learn more about the wiring in this car since maintaining a classic car isn't something I want to pay somebody else to accomplish for me.

100 bucks an hour for them to scratch their heads and Google shit? I DON'T THINK SO!!

Ground circuits don't cause fuses to pop. Shorts to ground and high amp loads do, but not poor grounds.
Looking at the schematic from Willcox, the orange wire 52 goes from the switch to the blower relay. Unplug the switch and relay, and ohm check for short to ground on orange 52.
My guess is there is a short to ground on your orange 52 circuit.
I don't know if there is a pass-through connector on the firewall, or if the blower harness is one piece that is routed thru a hole in the firewall. If there is a pass-through, dis-connect it and check for short to ground at both sides of the connector, ie. Ohm check the harness from the firewall connector to the blower connector, and from the firewall to the switch. That would tell you if your short is in the engine compartment or the cabin. That will narrow down the area of inspection.
Now, if the harness is one piece, and is routed through a hole, then you would need to trace the orange 52 wire from switch to blower relay, and inspect it for being pinched or rubbed somewhere.
Sounds more complicated than it really is. Basically separating the harness into short test sections and eliminating the good, while isolating the bad.
Firing dollars at a problem gets both tiresome and expensive.
Good luck
Jeff

Thank you for responding with some helpful advice. Yeah, after I posted that I thought about it for a day and decided it would do no good.
I have removed all of the switches and the blower relay from the circuit now.
I put the DVM in Comm mode, I think it is called, (little speaker icon). Makes an audible noise when you touch the leads together.
I put my red lead from the DVM on the Orange wire and grounded the Black lead to the Intake and nothing changed.
However, the Dark Blue wire made the audible noise.
Going to watch a few more you tube videos of these types of tests until I get this process down pat.
Thank you again.....

Just to close the loop on the thread I started. The issue has been finally fixed. Turns out replacing all of the parts was required in my situation. Don't exactly know why, but there wasn't a wiring issue in the car with this particular problem. The switch was bad, confirmed it was shorted out internally. A/C control switch was the actual culprit in all this I think because once that was replaced, most of the system was back to working again. All except the Hi setting on the fan. This was corrected by another new relay. Seems the first replacement was bad or went bad because other parts were still causing too much current to flow. The only thing that I did replace that didn't need to be replaced was the blower motor, but that was less than $20 and was original to the car....so no real loss there. I'll call that preventative maintenance.

I wonder how much trouble it'll be to move the fuse box from where it is to a better location in the car. What a pain it is to get to when you need to test things..... I still suck at electrical issues and will be trying to learn more whenever I can. I'll have to or go broke trying to keep an older car on the road.

Hello Goody,

I have a similar problem on my '81. The the whole blower shuts down intermittently on all speeds. It seems as though there is a loose connection somewhere. I don't think it is the ac switch because I replaced that as an assembly some time back. I know that the idle solenoid and the ac pressure switch are supposed to get power when the ac is turned on. Checking those today.

Being an electrical novice myself I think I'll throw some new parts at it. Ordered a new relay and resistor to start with. I don't want to have to pull that ac control head again. I hope it's not that switch. I can hit a bump and it will come back on. Another bump kicks it back off. Weird stuff.

I put an auxiliary fuse box on the engine side of the firewall under the steering column. All of my add on electrical products are wired to the new box. Fuel pump, alarm system, etc.

You just can't get to that darn factory fuse box to easily without this "tool" that I purchased. Simply reach in, clamp, and remove or install the fuse. Works great!

Glad you got it going!

Craig

https://cimg7.ibsrv.net/gimg/www.cor...e0ff1388d6.jpg

Hi Craig,
Seems to me you have a wire that is about to let go or a connector that is somewhat loose in either the plug or a splice location. That is why it comes and goes. I wouldn't look at new parts until you have scrutinized the plugs on all of the connectors.
I thought I had an issue once I put my console back together and found out that the A/C plug had come undone. You might be able to see that stuff by removing the ashtray and then shining a light through there for a peek. Maybe use an inspection mirror as well.
Another side project I have been giving thought to is to start replacing the old connectors and switch over to the new weatherpak types where possible. Can't do that for all of them, but there are some connections throughout the car that are just getting worn out.

Good idea with the hemostat.. was going to purchase some Kiwi pliers for the fuse box stuff. Getting too old to crawl up under that damn dash.....

Wiring issues on these C3's will make you feel like taking 1 step forward, then 2 steps back. Just when you feel you are making progress more gremlins pop up. If you could just wave your magic wand, a new complete wiring harness and fusebox, etc would solve all problems. If I were doing a complete frame off restoration it would be tempting to go ahead and replace all the electrical harnesses, etc. But otherwise you end up hacking away like the rest of us. Fortunately for the later models C3's that aren't worth that much to begin with, hacking is no big deal. On a numbers matching 427 big block '68 hacking WOULD be a big deal, and can eat into the value of the car.

Unfortunately you are probably correct about the loose wire or connector.
I think I can pull the console side cover back enough to see the control connectors.
I'll start there and then start chasing down some voltage measurements. :willy:
Oh boy.

Craig

The Culprit(s) Are Found
 

I did some poking around under the console today. Everything seemed to be ok with the fan and ac switches. Then I went to the blower relay. The terminals were very corroded and one had shorted out. Turns out this was the wire going to the blower motor. The blower motor wasn't getting 12v through the wire. I cut the bad terminal out so I could wire a temporary connection to the fan terminal from the relay. The yellow connector is what was connected at the blower motor ground. I hooked everything up today and blew it on all speeds on all ac settings. It's working great after finding and replacing these
https://cimg0.ibsrv.net/gimg/www.cor...c5c45edb77.jpg

Excellent find... :rock: