AC Hi blower issues 1975
February 24th, 2023, 10:42 AM
#1
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AC Hi blower issues 1975
Hi, new to sight and tried to post and “lost” it so here’s another attempt. Starting restoration on 1975 Salon coupe I purchased new. Only real issue I ever had with car was blowing inline fuse on AC hi blower/Relay circuit. Back then: when car was about 3 years old I started having AC blow fuse (in-line) & Hi relay intermittently. Never could root cause Dealer checked everything on system - a couple of times. pressures, flow, temps, leaks, circuits. Couldn’t find anything to cause. Basically, I carried spare fuse and Relay for the once or twice a summer it would die. Note that AC would still work, just not on high or on MAX. Also this is the manual AC system not the CAC auto temp AND no Freon or other service was ever required-system was never opened except to attach gauges at service ports.
Fast forward about 35 years. I purchased a low mileage 1975 “S” from original owner. Drove it occasionally - worked great until peak of summer. Same problem, replaced fuse and Relay. Dies intermittently, usually works Ok after replacing inline fuse.
Note: the Salon has rear window defogger, which was a “questionable” issue as the defog and hi fan were told me by dealer to “share” some circuits. Also that maybe accidentally turning on defogger while max AC was on was cause. That would be real easy to do since the cruise and defog switches are near identical rocker switches located next to each other on lower LH panel.
After I acquired the bone stock low mileage “S” and experienced the exact same failure so many years later, I’ve debunked that explanation as it doesn’t have rear defogger or cruise. Just identical failure mode.
As I start restoration on the Salon - I hope to resolve the problem for both cars.
Anyone out there ever have the issue? Old AC systems knowledge on possible problem. Possible old tech bulletin(s). Appreciate any responses! Tom
Fast forward about 35 years. I purchased a low mileage 1975 “S” from original owner. Drove it occasionally - worked great until peak of summer. Same problem, replaced fuse and Relay. Dies intermittently, usually works Ok after replacing inline fuse.
Note: the Salon has rear window defogger, which was a “questionable” issue as the defog and hi fan were told me by dealer to “share” some circuits. Also that maybe accidentally turning on defogger while max AC was on was cause. That would be real easy to do since the cruise and defog switches are near identical rocker switches located next to each other on lower LH panel.
After I acquired the bone stock low mileage “S” and experienced the exact same failure so many years later, I’ve debunked that explanation as it doesn’t have rear defogger or cruise. Just identical failure mode.
As I start restoration on the Salon - I hope to resolve the problem for both cars.
Anyone out there ever have the issue? Old AC systems knowledge on possible problem. Possible old tech bulletin(s). Appreciate any responses! Tom
February 24th, 2023, 11:09 AM
#2
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Join Date: Aug 2011
Posts: 3,060
Other than an intermittent short circuit to ground in the wire with the fuse for high speed or burned connections inside the fuse holder, I'd suspect the blower motor intermittently draws too much current during start up. With the fan on high check to see if the fuse holder gets hot indicating a high resistance/bad connection.
Are you definitely using the correct fuse? IIRC it's a 30 amp.
Good luck!!!
Are you definitely using the correct fuse? IIRC it's a 30 amp.
Good luck!!!
Last edited by Sugar Bear; February 24th, 2023 at 11:17 AM.
February 24th, 2023, 04:15 PM
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Yes, on using the correct fuse. I’d have to go check to type code letters, but know it was 30 amp and Definitely used what was specked. These are the old school Buss glass bodied fuses. I certainly get the possible short or intermittent short. And that could be very difficult to find. What bothers me is two different cars, with basically the same systems both having the same (exact) problem. Both being all stock and similar original low mile condition (even if one was 35 years later). Kinda leaves some of the faulty fan or fuse box stuff out of it - UNLESS - there was an issue back in the day. Possibly an only short duration problem - like one lot of fan motors or incorrect wire routing while Joe was on vacation or who knows? I just know I’m 2 for 2. Also, way back in the 80s my Dad had the Salon and when he tried to get a permanent fix he was told they were prone to have problems w/AC and to keep a lot of fuses on hand or don’t run max cool. I kinda blew that off as a bad AC guy until I had another same basic model and in original untouched low mile condition do the same thing.
Bottom line is I’m kinda trolling for anyone with a 75 or maybe 73-77’s or even just any Olds fans out there that had ever worked on, fixed, dealt with or was even aware of that issue. Hoping to get a lead on a known change/weak link/upgrade/fix. Last thing I want to do is have a freshly restored car that I’m trying to crawl over or tear apart troubleshooting wiring or other AC system issue on. Getting up under the dash is a big deal on that car. We loved that car. Perhaps the best, most reliable we’ve ever had, and that covers a lot of vehicles, years, miles and brands. :-)
Bottom line is I’m kinda trolling for anyone with a 75 or maybe 73-77’s or even just any Olds fans out there that had ever worked on, fixed, dealt with or was even aware of that issue. Hoping to get a lead on a known change/weak link/upgrade/fix. Last thing I want to do is have a freshly restored car that I’m trying to crawl over or tear apart troubleshooting wiring or other AC system issue on. Getting up under the dash is a big deal on that car. We loved that car. Perhaps the best, most reliable we’ve ever had, and that covers a lot of vehicles, years, miles and brands. :-)
February 24th, 2023, 05:14 PM
#5
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Join Date: Aug 2011
Posts: 3,060
"Bottom line is I’m kinda trolling for anyone with a 75 or maybe 73-77’s or even just any Olds fans out there that had ever worked on, fixed, dealt with or was even aware of that issue. Hoping to get a lead on a known change/weak link/upgrade/fix."
Blower motors drawing too much current on start up cause this as did burned connections inside the fuse holders. I asked for a picture of the fuse because how the fuse blew tells a story...
This ain't my first rodeo, good luck trolling and with your ride!!!
Post some pic's
Blower motors drawing too much current on start up cause this as did burned connections inside the fuse holders. I asked for a picture of the fuse because how the fuse blew tells a story...
This ain't my first rodeo, good luck trolling and with your ride!!!
Post some pic's
February 26th, 2023, 10:44 PM
#6
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Join Date: Feb 2023
Posts: 14
"Bottom line is I’m kinda trolling for anyone with a 75 or maybe 73-77’s or even just any Olds fans out there that had ever worked on, fixed, dealt with or was even aware of that issue. Hoping to get a lead on a known change/weak link/upgrade/fix."
Blower motors drawing too much current on start up cause this as did burned connections inside the fuse holders. …This ain't my first rodeo, good luck trolling and with your ride!!!
Sugar Bear, I honestly wasn’t trying to be annoying with that part of my comment. You have provided me some valuable info, especially with your last reply. I can’t provide the photos you requested because there are none and with either car in their current condition I can’t get any. As I tried to explain in previous post, the Salon first exhibited the issue when it was about 2 years old. I gave the car to my parents (actually sold it to them for the last couple of payments on it, when I bought a truck in spring of ‘78). We financed cars for only around 36 months back then. When it happened, I replaced the fuse and Relay, thinking fuses do t just blow without cause so perhaps relay points gone. When it happened again, I replaced fuse and it worked and because we were told we might have spiked the circuit by accidentally turning on rear defog while AC was on max (see previous post above). My dad later had same issue but I wasn’t there to know details. A point on that is it failed rarely - couple times a season in hot/humid south running on max & high quite often. Leading me away from a blower issue because it was so infrequent. Fast forward to the Cutlass S some 30 years or so later. That was basically a 30k garage kept time capsule. AC worked fine (it was from much colder climate & was probably rarely on max, if ever)
I brought it Texas 100+ temps. Drove it occasionally that summer, only to have same exact thing happen. Everything on car was original. I had to change belts/hoses, etc. to bring it home. Again, 15 or so years ago & I have no pics. It has set a lot since and carb needs rebuild, new tires and brakes gone through to be safe. Now, Your reply that I captured above - seems to be telling me a lot of good stuff. 1) it sounds like you’re the type guy I was hoping to hear from (“trolling” maybe not the best choice of words) and 2) sounds that you’ve dealt with and have much experience on the issue. On trying to give you info regarding the fuse condition and the limited experience I’ve had with it - the fuse connection was burnt/arched and/or corroded on at least one end. To the point , as I recall, the fuse cap end welded to the inside of the fuse connector terminal. The fuse glass either twisted loose from the end or broke in trying to remove it. The other thing you said was high blower current “on start up” caused this “as did”burned connectors in the fuse connectors…that sounded to me as being a bit more of a common problem. That said, I hadn’t really understood the “on start up” much because failure was always just going from a fan already running, to a higher speed. So, After your post I went hunting and found that “very generally speaking in layman’s terms” that most GM systems of that era; basically used the same setup: fused power from heater connection to blower switch, which then routed thru blower resistor(s) mounted on air box for low and medium speed fans and then thru, or more like “via”, the high blower relay (but basically was just “routed” through to the output terminal of relay to fan wire. Basically the relay only switched when the high blower was selected, sending a signal to the relay to switch to the 30amp power circuit (the high current, line fused, 30amp supply) and route that to output terminal and to fan. Thus current stopped flowing through one circuit (the blower switch/resistor circuit) and started flowing thru another (the line fused 30a circuit). Does that sound basically correct to you?
Based on that being somewhat the case: it sounds to me the high blower circuit was a bit weak or right at max/over with any spike loads from relay and blower, etc. The in-line fuse wire is a bit small for providing continuous high load w/max cooling circuit being on for long periods fighting 100+ Temps in traffic. The fuse connector also appears a bit weak (does it have little coil spring inside? Can’t remember) and also prone to moisture leak at split.
So, guessing - If the problem was somewhat common, maybe even more so in hot/humid climates; then maybe a little larger wire size and more robust in-line fuse holder? Thoughts much appreciated, Tom
Post some pic's
Blower motors drawing too much current on start up cause this as did burned connections inside the fuse holders. …This ain't my first rodeo, good luck trolling and with your ride!!!
Sugar Bear, I honestly wasn’t trying to be annoying with that part of my comment. You have provided me some valuable info, especially with your last reply. I can’t provide the photos you requested because there are none and with either car in their current condition I can’t get any. As I tried to explain in previous post, the Salon first exhibited the issue when it was about 2 years old. I gave the car to my parents (actually sold it to them for the last couple of payments on it, when I bought a truck in spring of ‘78). We financed cars for only around 36 months back then. When it happened, I replaced the fuse and Relay, thinking fuses do t just blow without cause so perhaps relay points gone. When it happened again, I replaced fuse and it worked and because we were told we might have spiked the circuit by accidentally turning on rear defog while AC was on max (see previous post above). My dad later had same issue but I wasn’t there to know details. A point on that is it failed rarely - couple times a season in hot/humid south running on max & high quite often. Leading me away from a blower issue because it was so infrequent. Fast forward to the Cutlass S some 30 years or so later. That was basically a 30k garage kept time capsule. AC worked fine (it was from much colder climate & was probably rarely on max, if ever)
I brought it Texas 100+ temps. Drove it occasionally that summer, only to have same exact thing happen. Everything on car was original. I had to change belts/hoses, etc. to bring it home. Again, 15 or so years ago & I have no pics. It has set a lot since and carb needs rebuild, new tires and brakes gone through to be safe. Now, Your reply that I captured above - seems to be telling me a lot of good stuff. 1) it sounds like you’re the type guy I was hoping to hear from (“trolling” maybe not the best choice of words) and 2) sounds that you’ve dealt with and have much experience on the issue. On trying to give you info regarding the fuse condition and the limited experience I’ve had with it - the fuse connection was burnt/arched and/or corroded on at least one end. To the point , as I recall, the fuse cap end welded to the inside of the fuse connector terminal. The fuse glass either twisted loose from the end or broke in trying to remove it. The other thing you said was high blower current “on start up” caused this “as did”burned connectors in the fuse connectors…that sounded to me as being a bit more of a common problem. That said, I hadn’t really understood the “on start up” much because failure was always just going from a fan already running, to a higher speed. So, After your post I went hunting and found that “very generally speaking in layman’s terms” that most GM systems of that era; basically used the same setup: fused power from heater connection to blower switch, which then routed thru blower resistor(s) mounted on air box for low and medium speed fans and then thru, or more like “via”, the high blower relay (but basically was just “routed” through to the output terminal of relay to fan wire. Basically the relay only switched when the high blower was selected, sending a signal to the relay to switch to the 30amp power circuit (the high current, line fused, 30amp supply) and route that to output terminal and to fan. Thus current stopped flowing through one circuit (the blower switch/resistor circuit) and started flowing thru another (the line fused 30a circuit). Does that sound basically correct to you?
Based on that being somewhat the case: it sounds to me the high blower circuit was a bit weak or right at max/over with any spike loads from relay and blower, etc. The in-line fuse wire is a bit small for providing continuous high load w/max cooling circuit being on for long periods fighting 100+ Temps in traffic. The fuse connector also appears a bit weak (does it have little coil spring inside? Can’t remember) and also prone to moisture leak at split.
So, guessing - If the problem was somewhat common, maybe even more so in hot/humid climates; then maybe a little larger wire size and more robust in-line fuse holder? Thoughts much appreciated, Tom
Post some pic's
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