AC electrial problem

[BarryK]

ok, this one has me boggled......

when I got my '78 (L82 with AC) the end of Feb and had it flatbedded home the first thing I did was go out and buy a new battery - the car didn't have one at all.
It sat untouched for about 2 months while i pulled the motor, cleaned and refinished everything than put the motor back in.
since I got the car running the battery has gone dead 5 or 6 times.

Ok, I figure it's one of two problems:
1. charging system not working correctly
2. a drain somewhere in the system.

I checked the charging system and it's fine. Good output from the alternator and good voltage back at the battery to charge it. No problem there.
That leaves a system drain ( of course, the HARD one to deal with - it can never be easy like the alt isn't working and i can have that swapped out in 10 minutes!)
I didn't get a chance to check thru the system to try to find the drain before taking the car into the paint shop (where the battery has already died 2 or 3 times in the 3 weeks it's been there!).

Wet to check on the car today and the painter tells me he thinks he found the battery drain issue purley by chance.
He had been sitting in the car, the shop was very quiet and he hears a very faint whirling sound. Turns out it was the climate control blower fan running slowly. The problem is the car was off and the key was out of the ignition!!
Moving the fan speed selection switch didn't make a different but he found that the top slide controle (the one that selects MAX AC, AC, HEAT, etc) had to be moved all the way to the left to the OFF position to get the blower fan to shut down.
WHY would the blower fan possibly be running with the car off??
This has to be the drain on the system that is killing my battery but I'm not even sure how to go about fixing something that I can't figure out how it could be broken. But broken it must be as the blower fan shouldn't be running with the car off, let alone with the key out of the ignition switch.
Maybe a relay gone bad and shorted out to show constant live power innstead of switched power on the blower??

 

[BarryK]

wow, no ideas from anyone??

ttt

 

[gmjunkie]

wow, no ideas from anyone??

ttt

Barry,you have a Bad Relay or a bad ground somewhere,Check all ground connections in the car!!! Expressly in the Eng. Compartment where you worked and painted!!!!!! Grounds make a electrical system do all sort's of Weird Things!!!!!!!!

 

[BarryK]

Hi Junk

yep, I know all about bad grounds, especially on Vettes.

there are only two ground wires that I can think of that I touched and that was the main big ground wire from the starter to the frame and that is a good connection and nice and solid and tights and the fresh paint was scrapped off before I attached the ground to it and I used a star washer on it also. The other ground wire is up front that connects to the coresupoort and that one is also nice and tight and done the same way.
Additionally, EVERYTHING else on the car electrically works great (except for a glitch on the wipers where I had to bypass the intermittent wiper function and just run them as OFF, LOW, HIGH).
i'll check my wiring chart but I doubt the wipers and the AC system are wired together in such a way to prevent the blower from turning off.

i'm thinking it's a relay also - just need to figure out what relay and where it's at.
A relay going bad isn't impossible by any means but in my experience in the car audio industry showed me that it's rare when it happens - at least it's rare when using good relays like Bosch but who knows what kind they used in this car.

 

[gmjunkie]

Barry,There should be a ground Eng to frame, and also check ground to blower motor it's self! and there should be a ground from frame to bird cage,this one may be the culprit,it's right behind the Lt.Front wheel and is hard to see if the shield is in place!!! I've had problems there before!! P.S. this could also be your glitch in your Wipers!!

 

[KOPBET]

I'm from the old school that believes than in electrical circuits with discreet components bad grounds prevent electrical flow and not create it. So I would start by removing the heater/ac fuse and check to see if the fan still runs with ign switch off. If not then replace the fuse and work back towards ign. switch for electrical short in harness or bad ign switch. If the fan still runs with the fuse out work back toward selector switch for short in IP harness.

 

[Artsvette73]

I would disconnect the blower switch. seeif it stops. Those switches and connector were not of a robust design for the intended use.

 

[KOPBET]

I would disconnect the blower switch. seeif it stops. Those switches and connector were not of a robust design for the intended use.

That'll pretty much stop it ...

 

[JohnZ]

He had been sitting in the car, the shop was very quiet and he hears a very faint whirling sound. Turns out it was the climate control blower fan running slowly. The problem is the car was off and the key was out of the ignition!!
Moving the fan speed selection switch didn't make a different but he found that the top slide controle (the one that selects MAX AC, AC, HEAT, etc) had to be moved all the way to the left to the OFF position to get the blower fan to shut down.
WHY would the blower fan possibly be running with the car off??

At some point in the late 70's, GM A/C systems were designed to have "full-time low blower" to maintain airflow through the evaporator so it wouldn't freeze up if the A/C was on but the blower switch wasn't turned to "on". I don't recall what year or which models, but that feature only worked with the key in "on" or "accessory". I think that was mentioned in the A/C section of the owner's manual so people would know why the blower was running all the time - take a look in the manual and see if it's mentioned.

 

[BarryK]

thanks guys, as soon as I get the car back hopefully nest week I'll check thru all those ideas.

John, What your saying makes sense but it still wouldn't explain why the fan would be running on low speed with the key in the OFF position, let alone with the key out of the ignition switch.That's what has me so confused on this.
I would think the entire system was on a 12v switched circuit so with the key off it should all be completely off.

 

[gmjunkie]

At some point in the late 70's, GM A/C systems were designed to have "full-time low blower" to maintain airflow through the evaporator so it wouldn't freeze up if the A/C was on but the blower switch wasn't turned to "on". I don't recall what year or which models, but that feature only worked with the key in "on" or "accessory". I think that was mentioned in the A/C section of the owner's manual so people would know why the blower was running all the time - take a look in the manual and see if it's mentioned.

I think that was in 76or77, John!! But I've slept since then you know I'm getting old and forgetful!!:W :W

Barry, Unfortunately my 78 Shop manual is in my 78 at the house in Florida!!! But here is a page from the 79 manual. I couldn't find location of relay but I think it is around the Fuse box or the A/C evaporator housing on the out side close to the fan speed resistor!! 1st column near bottom of attachment!!

 

[BarryK]

thanks Junk - the answer may just be in there. It says (hard to read it was small but I quinted and got real close! ) that if the blower operates with ignition off it's a malfunctioning ?? blower relay (closed contacts)

?? = I couldn't read the word


sounds exactly as I had suspected.

As soon as the car is back from the paintshop I'll start looking for that relay.
I've been looking at my wiring diagramn from Don Olsen and even on that I can't seem to locate the relay. I guess it's a manual search thru the car..... gee, how fun!

 

[mkapp7879]

Barry, there's a couple of wires that plug into the front side of the fuse box, one is for the key buzzer and there is a big orange wire plugged in next to the heater/AC fuse. Looking through the wiring diagram last night(until I started going cross eyed!)I see a large gauge orange wire that appears to SUPPLY power to the AC and turn signals. Originally thought it was for the defroster but now don't think so. It's a ign on only circuit. Could you have a wire plugged into a batt. slot? Nothing plugs into the batt. slot of the fuse panel. I have a photo of the 78 fuse panel if you want to see where any wires plug into it. Also, see if you have turn signals with the key out. Just something I noticed in the wiring diagram. Mike

 

[BarryK]

Mike

I see on my wiring diagram what you are referring to. The orange wire goes from the ign switch to the one sid of the AC/Heater fuse. The other side of the fuse is a brown wire that goes to a connection than to the heater switch.
As you say, it looks as if that orange wire also feeds the directional signal fuse position.

There was an aftermarket alarm installed on the car when I bought it that I removed. I know I reconnected the wires together properly BUT it's possible when they originally installed it they switched a wire around incorrectly although with the age of that alwarm I can't imagine any previous pwner not having this fixed IF that was the case as the battery would be dead for them every 2-3 days unless they had a battery cut-off switch.

Looks like I have two things to check out now, that orange wiring up at the ignition switch to make sure it's on the correct connector so it's on the "OFF" connector to turn off power to the circuit or the relay.
I'm leaning towards a better chance that the relay is bad though - it makes more sense. I know alarm installs and there would be no reason to go to the actual ignition switch and change that connection, especially on that particular circuit - unless they spliced into it somewhere in the middle and than it got reconnected to a hot lead rather than a switched lead......
with Bubba obviously having been there anything is possble!