Heater temperature control problem

[greg geraci]

I have an 89 sho and heater stays on in high position. Although I change the climate control to lower temperature heat remains high. the climate control does operate properly the closing and opening of the floor vents, dash vents as well as the defrost.

1. I don't know if the only valve control is in the heater tube under the hood that leads into the heater core.
2. How does the heater valve tube under the hood opens and closes weather its due to vacuum or electrical. it looks like a electrical connector that plugs into it
3. How does lowering the temperature on the climate control send the signal to what ever valve controls the hot water flow.Does the climate control send electrical or vacuum
A response would be very much appreciated
sincerely
gg

 

[projectSHO89]

Temperture control of the airflow is achieved by a movable door inside the A/C plenum under the dash, not via coolant flow control. That electrical device in the heater hose under the hood is the CELO switch (Cold Engine Lock Out). It is supposed to prevent interior windchill by keeping the blower speed low until the core is actually receiving warmed coolant.

The blend door actuator (BDA) is a small motor, gear, and sensor assembly that sits on the top of the HVAC plenum and is the usual problem. Replacemnt requires pulling the whole dash back.

Run an EATC self-test and see what code, if any, pops up. Probably a "02".

The Blower Speed Control module controls the blower speed. They often fail, leaving the blower running on high speed. It's pretty easy to replace.

Both suspect parts are not unique to the SHO and should be available through any Ford parts source.

Steve

 

[greg geraci]

Thank you Steve,
My blower speed moduale seems to be working, because i do have different fan speeds and I do have control over the dash vents and floor vents as well as the defrost vents. I just can't change the temperaature when I tell the temperature to change on the climate control via 90 degrees to 70 degrees. when I put it on 70 degrees it still will blow out hot.Does the climate control tell the blend door actuator to open and close and is it done through vacuum.

I really want to thank you for taking the time to help me.
p.s. Who would you reccomend to do the work if I can't pull the dash myself.I live in huntington Beach .

 

[projectSHO89]

Does the climate control tell the blend door actuator to open and close and is it done through vacuum.

Yes. No.

The BDA is electrically controlled.

Run the self-test BEFORE YOU DO ANYTHING ELSE!

Seems there is a fuse that runs only the BDA. Let me see what I can dig up. EDIT: F17 on some models. Not certain of the 89. EVTM is in the basement and it's cold downstairs....

Welcome aboard the forum. Happy to help.

See if you can find the guys taking over the SHO stuff from SHO Shop. Maybe they're close enough to be of assistance. Just starting out, they can use the business.

Steve

 

[shoguy57]

does the same hold true for the 94 model year? my situation is simillar except i have no heat. I get a blend door failure code and the lines going to the heater core are both hot. not really interested in taking the dash out if at all possible. Would like to know if it is just a fuse.(boy would that be nice!)and where would the fuse be located?

 

[Fourcats]

We installed an inline push/pull {shut/open} valve in the the inlet "S" hose that goes into the fire wall, from the engine. {Its under/behind the EGR valve}

 

[greg geraci]

Did you ever get an answer if there is a fuse in line for the climate control to actuate the blend door
Greg