jd25q

Hi all,

This was my dad's car and had been sitting a while. I changed out the heater core as it was leaking. This was in the spring, now as it's colder I'm noticing no heat. The heater hoses seem pretty hot so I think there is hot coolant going back to it. I took out the glove box and the blend door actuator seems to be moving full travel when the heat setting is adjusted.

Is there a way to access the blend door from the interior side? I would like to be able to see it to judge if something is blocking it closed, maybe a mouse nest or something in all the time this thing sat.

Also, could it be a thermostat? It feels hot, hard to keep my hand on the heater hoses. I've got a replacement for that so I'll look at it anyway as I'm switching upper and lower radiator hoses.

Thanks for any ideas,

jd

brichar8

I'm sorry I don't have any ideas to help you. I'd like to see some photos of your Ninety Eight. I have some here of my three 84' Ninety Eights.

76olds

Are you sure the vacuum lines are plugged in the same way you took them off at the heater box? Also did the heater box go back into place easily? If you the heater box isn't sealed properly to the firewall you will not get proper heat.
Also when you refilled the rad did you see coolant flowing through the tubes prior to topping it off with coolant and capping the system? If these procedures are all good, we can go further on diagnosing the problem.
Hope this is a good starting point,
Eric

rocketraider

Is this a Tempmatic car or manual control A/C?

jd25q

Thanks for the replies,

I guess this is a manual a/c (has the slider to select temperature).

I've been under the dash a little and I think the problem lies in the vent blend door. The blend door behind the glove box is working fine. Only problem is that there is cold air blowing in through the rectangular cutout for the blend door rod. This is not the source of the problem, but it is not helping. Should there be some type of foam gasket there?

I noticed last night when I put it on heat there is some warm air, no where near as hot as it should be blowing out the bottom. Defrost works too, same temperature.

When I put it on vent at maximum temperature, ice cold air through the upper vents, though not much of it. Most of the air is coming through the heater vents, and it is as hot as you would expect for full heat.

The vacuum hiss when I switch to vent goes on for a very long time. Wondering if I don't have a leak. Is there a second blend door under their? How would I get to it?

Thanks,

jd

rocketraider

If the temperature lever has numbers 65 to 85 along its length it's Tempmatic. If no numbers, just a band that changes from blue at the left to red at right, it's manual temperature control.


Tempmatics have a programmer that goes wonky sometimes and usually manifests itself as full cold when you want heat or full hot when you want A/C.


The extended vacuum hiss tells me either a large leak (probably a vacuum motor) or possibly a leak on the vacuum selector valve on the control head- the function control lever operates it. There's a thin rubber diaphragm in there that routes vacuum to the correct doors for the lever position, and after 30 years could well be shot.

jd25q

OK, well it's a tempmatic. The hot and cold range seems to be working, just that I only get full heat when it's on vent. Will I need to disassemble the dash to get to this?

Thanks for the ideas

rocketraider

Depending on where the faulty motor or door is, you might have to. You need a 1984 Chassis manual and big car Electrical manual to figure out what's gone wacky and how to get at it.


You can get to the Tempmatic programmer by taking out the glovebox. To get to the HVAC control head, remove radio ***** and lighter, then there are (I think) 3 screws above the radio and lighter panel. You can then pull the trim panel straight out and get to the control, radio etc.


If panel has never been out it may take a little persuasion. If you can hook your fingers into one of the openings you should be able to pull it out.


If it were just the full cold or full hot problem, there's a round vacuum checking relay on the Tempmatic programmer that is almost always the cause of that problem. Full heat only on vent tells me vacuum motor or control problem.

jd25q

Thanks for the info, I'll give that a try,

stressed1

Check the vacuum line. you may have knocked the hose off the ball on the passenger fender when doing heater core.

1970cs

I actually pinched a vacuum hose between the fire and air box inside the car. But that would not switch the door from anything but vent.

Pat