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82 blower fan pops 25amp A/C fuse

 
Old 05-11-2019, 08:42 PM
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Goody
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Default 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.
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Old 05-12-2019, 08:32 PM
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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..
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Old 05-12-2019, 08:51 PM
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See if fuse pops when blower is not hooked up. See if a lighter fuse blows with blower unhooked.
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Old 05-13-2019, 09:09 AM
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Originally Posted by fishslayer143 View Post
does it blow fuse instantly or does it take a little time?
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.
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Old 05-13-2019, 09:12 AM
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Originally Posted by derekderek View Post
See if fuse pops when blower is not hooked up. See if a lighter fuse blows with blower unhooked.
Hadn't thought of or tried that yet, I'll give it a try today after work.
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Old 05-13-2019, 08:11 PM
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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.

Last edited by Goody; 05-14-2019 at 03:40 PM. Reason: update
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Old 05-19-2019, 03:09 PM
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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.
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Old 05-19-2019, 03:15 PM
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100 bucks an hour for them to scratch their heads and Google ****? I DON'T THINK SO!!
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Old 05-20-2019, 06:43 AM
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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
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Old 05-21-2019, 09:50 PM
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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.....
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