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66 Fleetwood - strange A/C issue

Started by scotth3886, May 17, 2022, 02:07:42 PM

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scotth3886

A/C has been working fine, BUT lately as temps get up into mid 80s I have noticed that I get high blower speed and super cold air if car has been sitting for a few hours or all night.  However, I noticed that if the car is fully warm, as warm as it gets, temp gauge between 1/8th and 1/4, and I shut it off and it heat soaks for 15 minute or so, it seems like I lose the high blower speed until it completely cools down again and then it works fine until I shut it down again.  If i keep driving without shutting it down, I have the high blower speed and no issue.  It's not icing up or anything as it's definitely the blower speed.

I know there's probably a real simple answer, but I'm not sure where to start. (yes, I have the book)

Thanks

"Cadillac Kid" Greg Surfas 15364

Scott
Check the electrical connections at the blower relays. That area is subject to extreme heat. Unplug the connectors, inspect and clean them up
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

scotth3886

Quote from: "Cadillac Kid"  Greg Surfas 15364 on May 17, 2022, 02:28:57 PM
Scott
Check the electrical connections at the blower relays. That area is subject to extreme heat. Unplug the connectors, inspect and clean them up
Greg Surfas

Thanks.  I'll give it a try.

cadillactim

Scott

Is high blower speed on Auto or Auto Hi? Auto Hi bypasses the power servo and sends direct battery voltage to blower. And what happens in Ice, high speed blower or not when this condition happens?

Tim
Tim Groves

scotth3886

Quote from: cadillactim on May 17, 2022, 05:37:16 PM
Scott

Is high blower speed on Auto or Auto Hi? Auto Hi bypasses the power servo and sends direct battery voltage to blower. And what happens in Ice, high speed blower or not when this condition happens?

Tim

I don't feel much difference between auto regular and auto high.  I hear a little difference but that's about it.  The fan speed reduction happens in both setting, which I can feel and hear. 

Car has now cooled off in the garage since my first post and I now have the high fan speed back again.  It'll be fine until I stop somewhere for 15 minutes or more and then high blower speed is goner until the car cools back down for a few hours.  It doesn't overheat ever at all.  Highest temp I see with a heat gun around the t-stat is 180 degrees, same as the t-stat.

cadillactim

Scott

When this happens is there no blower or low blower?

If no blower see if the diaphragm on the vacuum master switch is pulled up all the way. If not, sounds like a vacuum issue.

If low blower see if arm on the back of the power servo is out all the way. If not, disconnect and plug vacuum line going into large diaphragm in power servo. If blower is on high speed then, the issue may be sensor related.

Tim

Tim
Tim Groves

scotth3886

Quote from: cadillactim on May 17, 2022, 06:43:06 PM
Scott

When this happens is there no blower or low blower?

If no blower see if the diaphragm on the vacuum master switch is pulled up all the way. If not, sounds like a vacuum issue.

If low blower see if arm on the back of the power servo is out all the way. If not, disconnect and plug vacuum line going into large diaphragm in power servo. If blower is on high speed then, the issue may be sensor related.

Tim

Tim

It loses its highest blower speed.  It's on medium speed when this happens.  Now that it's cooled off for four hours, it's all back now so I'm going to head out to the garage and fool with it a bit.

scotth3886

Quote from: cadillactim on May 17, 2022, 06:43:06 PM
Scott

When this happens is there no blower or low blower?

If no blower see if the diaphragm on the vacuum master switch is pulled up all the way. If not, sounds like a vacuum issue.

If low blower see if arm on the back of the power servo is out all the way. If not, disconnect and plug vacuum line going into large diaphragm in power servo. If blower is on high speed then, the issue may be sensor related.

Tim

Tim

It was still warm enough that it did it again when I ran it for 10 minutes or so then shut it off and let it sit for 10 minutes or so and restarted. 

Attached are pics of the power servo arm with the A/C off and then with it on stuck in the low or medium speed fan. 

Also, with just the finger, I don't feel any vacuum at the line going into the power servo. 

cadillactim

Scott

Try this to see what happens. When the car is warm and no high speed, put direct battery voltage to blower motor and see if you then get high speed blower in the car. Your power servo arm looks okay, wondering if it could be blower resistors in servo.

Tim
Tim Groves

scotth3886

Quote from: cadillactim on May 18, 2022, 08:14:31 AM
Scott

Try this to see what happens. When the car is warm and no high speed, put direct battery voltage to blower motor and see if you then get high speed blower in the car. Your power servo arm looks okay, wondering if it could be blower resistors in servo.

Tim

That sounds more like it or if this has a bad blower relay.

Raining this morning, and to do anything on the car, I need to get the back far enough out of the garage that I can get the hood up.  The car is 3" longer than the garage.

I still think I need to replace the power servo with a rebuilt one from you but haven't gotten to it yet.  Can the power servo be replaced without pulling the air box away from the firewall?  Wondering if it's something a senile old man can replace himself? 

"Cadillac Kid" Greg Surfas 15364

Scott
Did you check the blower relay and connections.? High (est) speed fan goes through the relay. If heat compromises the relay or connections you loose high. Had that happen a couple of times on my 66.
GregSurfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

scotth3886

#11
Quote from: "Cadillac Kid"  Greg Surfas 15364 on May 18, 2022, 12:32:10 PM
Scott
Did you check the blower relay and connections.? High (est) speed fan goes through the relay. If heat compromises the relay or connections you loose high. Had that happen a couple of times on my 66.
GregSurfas

This is what I suspect it is.  I checked all of the connections, but I got to double check as to which is the blower relay is.

Yeah, that's gotta be it.  I haven't touched the car since last night so I just went to the garage and gave it a try.  Car is as cooled off as it's going to get.  High blower speed is back and it all works fine.  Almost has to be that relay.   I still think that I'm also going to replace the power servo with one of Tim's rebuilt ones.

"Cadillac Kid" Greg Surfas 15364

Scott
Those relays are cheap. I would try replacing the relay before I went any further  but that is just me
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

scotth3886

#13
Quote from: "Cadillac Kid"  Greg Surfas 15364 on May 18, 2022, 01:45:25 PM
Scott
Those relays are cheap. I would try replacing the relay before I went any further  but that is just me
Greg Surfas

Do you get the relays from ebay or some other source?  I'll do this first (I only change one this at a time) and the power servo a little later.  Everything is original concerning the HVAC so I'll probably have a few more things to replace in the future.

It appears that Four Seasons part # 35760 is the correct part.

"Cadillac Kid" Greg Surfas 15364

Scott
It seems like all the current relays are about the same in quality. Rock auto has four seasons and standard which are about the same. I would buy 2 since the new ones don't seem to last that long with all the current they carry.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

scotth3886

Quote from: "Cadillac Kid"  Greg Surfas 15364 on May 18, 2022, 03:21:48 PM
Scott
It seems like all the current relays are about the same in quality. Rock auto has four seasons and standard which are about the same. I would buy 2 since the new ones don't seem to last that long with all the current they carry.
Greg Surfas

Thanks for all of your help with this.  Off to Mecum Indy and I'll get this ordered when I get back.

scotth3886

I ended up ordering the relay before I left for Indy with hopes that it would get here Saturday so I can get this fixed.  It did get here so I gave it a try today.  Today was low 70s so I'm not absolutely sure it's fixed yet until it gets 80s or 90s. 

Took the old one off and noticed that the ground wire wasn't connected to anything other than the occasions it might have been laying against the block or on top of the bell housing.  So at least today in the moderate temps, it seems to be fixed.  I finally have a huge difference between auto low and auto high settings, leading me to believe that it is fixed.

"Cadillac Kid" Greg Surfas 15364

Glad it worked out. Simple things first.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

scotth3886

Quote from: "Cadillac Kid"  Greg Surfas 15364 on May 23, 2022, 10:55:03 PM
Glad it worked out. Simple things first.
Greg Surfas

Thanks again.  Had it not been for Tim and your suggestion regarding the relay, I would have never found the ground wire that wasn't connected to anything. 

The HVAC now reminds of what I remember working for a Cadillac dealer then Olds back in the day that this was a new car.

scotth3886

As a follow up on my A/C issues: I've now had the car out and around on near 90 degree days with hot soaks in the sun with the car closed up and a few chilly days when some heat was needed in the morning.

System seems to work perfectly now after fixing the situation with that hi-speed blower relay ground wire that wasn't attached to anything. Set it at about 70 and it will blow heat in the morning and transition to A/C as needed when it warms up outside.  It works just like I remember when I worked in a local dealer when these were new cars. It's truly set and forget.

It's nice having something that's an easy fix once in a while.  It doesn't happen often.