93 deville no heat issue

[russ austin]

I'm working on a 93 deville that has a no heat issue with the heater. Cold air is coming out of the floor vent. Last year I changed the heater core and that only got semi warm air coming out.
Now I have checked everything over and it al checks good.  I changed the control box on the side of the heater core, made sure the hose routing to the heater core is correct, the mode door is working, vacuum pods work and hold vacuum, vacuum to the vacuum pads, no vacuum leaks in the system. Changed the thermostat too. Coolant level is good.  Plastic T fitting with the restrictor is facing the heater core. 

Can I plug the heater core bypass hose?  I don't see the purpose of the bypass system for the heater core.

[gkhashem]

Russ

I will admit I am a novice compared to some on here but....

On my 1959 Oldsmobile, I had vacuum and all but no heater core flow after flushing the core and finding no vacuum leaks.

Well my heat control valve was not opening. Vacuum was not able to open it to allow coolant flow to the core. Now on my 1959 I guess the default is no flow? So cold air.

https://www.rockauto.com/en/catalog/cadillac,1993,deville,4.9l+v8,1025750,heat+&+air+conditioning,heater+valve,6860

Could it be not opening for you to allow good flow?

[russ austin]

I appreciate the follow up, but the T fitting is just that, no valve. One side has a restriction to slow the amount of coolant in.  The shop manual doesn't state what way the T fitting goes in, but I did find info that an arrow id=s in the direction to the heater core. of course the repop T fitting doesn't have an arrow. 

[gkhashem]

So I assume you replaced it or is working? Maybe it is gone or defective?  Is there a hose after the fitting is it hot?

But I assume you checked that. The older car were much easier to work on. The only other suggestion is look in the shop manual for no heat conditions and maybe there is a trouble checklist of things to look at.

[Cape Cod Fleetwood]

Change the thermostat again, this happened to me. The new one was a bad one. Cheap part and easy replacement. YMMV

\m/
Laurie

[gkhashem]

Yes could be but again if that was the case then is the radiator hoses getting hot then there is flow.

If not you would think it would run hot or over heat if that was the issue.

[TJ Hopland]

Are you sure the blend door is working properly?  I have seen issues where the actuators are moving but the actual door is off its pivots or something like that.

I'm assuming Russ knows what I am speaking of because he would have had it all apart to do the core but for others that have maybe so far been lucky enough not to have to know how a typical car system works the typical air flow is:

-recirculate or fresh air intake controlled by the recirculate door.  Its either sucking air from outside or from inside depending on the position of the door.
-blower
- AC evaporator.  All the air always flows through it.  Other parts of the system control if its cold or not.
-blend door which either directs air through the heater core or around it depending on the position of the blend door.
-mode doors which direct which vent or vents the air comes out of.   Often is more than one door working together. 

[harvey b]

is there a timing sequence for the doors to open,i know the early  2000's chev trucks with seperate controls for each side have a procedure to do so they are both in sync?,they have a series of actuators that control the air flow,if they are messed up you have either too much heat or cold?.Might be something to look at,I know the caddys use the A/C all the time for defrost,possibly unhook the power wire to the compressor for a few minutes and see if it improves,that might give you a place to start. good Luck   Harveyb

[russ austin]

Fixed the issue, the car now has heat.  Turns out I was sold the wrong heater core. Orielly and Auto zone both list the wrong part. The part they list is for a manual temp controlled car. Last Cadillac I know that had manual temp control was the 63. The rest have the temp you set and the car takes car of the rest.

Auto zone had this in their books, Part # 90480 for an automatic temp car.   They are  both identical externally, but the wrong one I was sold has already clogged up partially.

[gkhashem]

I guess the simple analysis was the best.

On an old car you see if there is flow through the core. You feel to see if the hoses are hot in and out. I guess in this case there was none.

So why was it restricted. Some computer climate control issue?

Just curious.

[Cape Cod Fleetwood]

Glad you're fixed! I get a lot of parts from Autozone, NAPA, etc.
Sometimes they work....

\m/
Laurie

[russ austin]

I guess the simple analysis was the best.

On an old car you see if there is flow through the core. You feel to see if the hoses are hot in and out. I guess in this case there was none.

So why was it restricted. Some computer climate control issue?

Just curious.

The AC is always on unless you shut the system off.  The heater core always gets hot water through it.  The blend door is what selects the air to go over the desired part. (evaporator or heater core).  Everything worked except the wrong/blocked up heater core.