I had been feeling heat coming out of the center lower vent, but the fan wasn't working, found a bad fuse, fan works great now. Had the car out last night with my wife and it was cool, so we turned on the heat.

The air did not seem hot, as it had been, once I had the fan running, and it didn't seem to be warming up our environment.

The flow of air was actually most noticeable with everything off, and we were getting what felt like outside temp air rushing into the car.

I can hear the flap move when I switch from cool to hot with the fan running, and the sound of air rushing changes, so I think that works, and switching from heat to defrost stops the flow of air from the lower vent to the windshield (though it doesn't arrive, I think the vent system has too many misalignments and leaks from what i recall of taking it apart 15 years ago or more), so I think the heat setting on the dash control works.

Any thoughts? I am going to start pulling things apart to see if a vent is open somewhere. The car was originally a non-ac car, and the AC was installed by a guy who owned the car and worked at the dealer in the early 70s, so it's factory AC, but there are vents behind the side kick plates under the dash. Not sure if these could be the issue, or if it's all from the heater control.

Could this be a heater core issue? I did replace the heater core about 17 years ago, but in terms of miles, it hasn't been used a lot, and I was feeling warm air when the fan wasn't working, it's just that blowing the fan on high hasn't improved the heat situation. that's the mystery.

 

Well, if this "factory AC" retained the non-A/C fresh air vents in the kick panels, it isn't a factory installation (there's a recirculating flapper door that goes in the passenger side kick panel, for example). Unfortunately, that means that we don't know what else was done and if it's really a factory installation or not. This matters because the only advice we can offer without seeing the car and knowing how the A/C was installed is to ASSUME it works like OEM, but clearly there is at least one deviation and there may be more.

For example, is there a heater control valve at the rear passenger corner of the intake? If so, is it the correct normally closed style for your car or a later normally open style? This could certainly cause the problem. It could also be caused by the heater core being plugged, or the temp selector door not being adjusted properly.

 

I presume you mean intake manifold? I'll take a look. It wasn't a factory installation, definitely this guy got the parts from the dealer and installed it himself. Everything looks factory, but the driver's side kick panel has the holes for the manual vent controls, that was the giveaway, and later my Dad ran into the former owner, this was probably 25 years ago, and he filled him in on what he did to the car (swapping blue interior for white when he painted car white, adding ram air scoops, etc.).

How would I diagnose a plugged heater core on this car?

I'm going to pull things apart, later today probably, I just discovered a plumbing leak in my basement (slow) that I think I'll take care of first. So much for a slow day...

I appreciate your thoughts. I'll take pictures of anything that looks interesting or helpful.

 

OKAY, good news, heater control valve was stuck closed due to vacuum line being disconnected and hanging by the firewall. I still have one extra vacuum line sticking out of the fire wall that I can't identify (old cruise control line maybe?), but the heat works great now!! Also found a vacuum leak at the distributor so fixed that as well... thanks for your help, problem solved.

Quick question, is it a good idea to plug the mystery vacuum line that is sticking out of the firewall?

 

Better trace those vacuum lines to figure out where they go. A factory A/C setup should only have two vacuum lines going through the firewall. One goes to the heater control valve. The other goes to the vacuum tank, and from there to the intake manifold to supply vacuum to the system. If you have vacuum to operate the heater valve, it's coming from someplace. Do the vacuum operated flappers under the dash also work? If so, you need to figure out what this mystery hose is connected to.

 

Plumbing leak fixed with shark bite connectors, first time i used those, so far so good today...

I would assume the flappers do work, because when I switch from heat to defrost to vent for example, i get air from all the right places, even if weak due to leaks in the ductwork.

I've got something screwed into the manifold with three ports on it, I don't recall if it has ever been connected to something since I've had the car (mid 1980s).

I'll see if I can attach pics of what I have. I can't find the old Chilton manual for the car, it's been misplaced, not sure if it'd be in there anyway. The first pic is of the three port mystery part, which I have always thought was non-functional. The second shows the mystery vacuum line sticking out of firewall, and the third shows the vacuum line that had become disconnected from the heater valve.

 

The car is set up for cruise control but it has never worked, I'll trace those vacuum lines and see if they would have run through the firewall in the same spot.

 

"Lost" is a good place for a Chilton manual, second only to "in the trash". Get yourself a real Olds Factory Service Manual. Get a used original on ebay.

The three port fitting is the thermostatic vacuum switch for the vacuum advance. From the factory, the distributor vac advance ran from ported vacuum, which can cause overheating in traffic. The TVS was designed to switch the distributor to full manifold vacuum if this happens. If your car has this bypassed and is running off of manifold vacuum, that's fine.

The third vac hose may be the vacuum dump for the cruise control, but the hose looks small. If it is the vac dump, it will run to a switch on the brake pedal.

 

Thanks. I presume if it's attached to the switch on the brake pedal (which I'll look for), then it's not in the vacuum circuit? I'll plug it just to be sure. I really appreciate all your help. Yes, I don't remember Chilton having a lot of information, but it came in handy in the old days. I'll look for the real manual.

 

Well, actually it is a vacuum circuit, but it would be part of the non-functional cruise control and thus not active at the moment. The brake switch is used to quickly release the vacuum in the cruise control actuator when you hit the brakes to disable the cruise, since presumably you are trying to stop. Again, not an issue if the cruise is not working now.

 

Tnx