brealytrent

So contrary to what seems to be the most common problem of heat all the time, I have no heat, all the time. However I know the line isn't plugged/ valve stuck because if I shut the car off and come to start it 5 minutes later, I'll get a little heat for about 30 seconds until the coolant in the heat exchange cools back down.

Speedtoys

Low coolant level?

brealytrent

...coolant level is good.
NEXT

Calgary Ole

Stuck temp. setting motor?

brealytrent

where would I find that contraption? Do '84s have those?

Speedtoys

Up under drivers dash, right knee level or so.

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Or..adjust it...link....somewhere...

Calgary Ole

Yes I think so. Hopefully others who no more will confirm.
On mine, it is mounted between the sterring column and the heater box in the center console. I beleive early cars it is inside the heater box .
When you move the temp slider from hot to cold, it opens or closes the heater valve via vacuum to blend hot water from the engine to maintain desired cabin temp. Great system if all the vacuum actuators are working properly. In changing weather it will constantly adjust the amount of hot coolant into the hvac system to maintain the temp you have selected.

tailpipe

thermostat could be stuck open had one of those here.

jcorenman

I assume you've changed the heater control valve? (Right-hand side, back of the engine under the air filter).

brealytrent

Could be that, does always run just below the first white line. Although it is cold out and it has an aluminum radiator. You'd think I would still get some heat then.

brealytrent

No I have not. However like I stated earlier, it seems like it is functional as after shutting down and losing vacuum the heater core does get hot and I get a small burst of somewhat warm air after starting again. I know one can't really tell if it's good from just looking, but it does appear to be a newer unit as well, including the short hose.

Alan

Well to be sure - just disconnect the vac line to the water valve - pretty easy.

Your head unit sensor loop could just be shorted out to ground. If the heater valve opens with vac disconnected and the mixing flaps always stay closed (check the mixing flap motor to see if it moves when you move the temp slider....) - seems likely its a sensor loop electric connection issue (ground short)

Alan

brealytrent

Thanks for all the replies, everyone! When I get a little time I'll have to go and try all these different ideas. I'll report back my findings.

StratfordShark

Up to a point! The setting motor (electric) blends air from outside with air passing heater matrix. The heater valve itself is still controlled by vacuum as you correctly say, but from the hvac vacuum manifold solenoids buried in centre console.

If air is always cold my first check would be to sit in car in quiet spot with ignition on. Push temp control lever to full cold. Should hear the setting motor move to cold position (arm at lowest point if you squirm into position so you can see it working).

Push lever all way to hot. Does setting motor arm move to top position?

Is the thin metal arm which controls mixing flap on heater box connected to the setting motor? It's attached via a nylon bush and it can pop out, in which case the setting motor will work fine, but if the mixing flap is in cold position you won't get any warm air.

Alan

This is actually quite incorrect... The heater core will usually have a flow of (hot?) coolant unless the temperature slider setting is calling for a very low or min temperature. Temperature control is always controlled dynamically by the setting motor moving the mixing flaps to control what % air flows through vs around the heater core - that is always the primary automatic temperature control mechanism. When the AC is switched on it is likewise also on continually and the temperature control is still maintained by heater core airflow mixing flaps.

The water valve doesn't cycle much in normal use, and is usually on. Similarly the only thing that causes the AC to cycle when it is switched on - is the saftey equipment (freeze switch & pressure switch) it doesn't cycle for normal cabin temperature control.

This operating mode is for some reason not intuitive to most (nor me originally...) but it is the simplest control mechanism for this system configuration.

Alan