Heat or testing heat

[llhat]

1989 Comanche with A/C  4.0

 

some help with possible diagnosis of heat in regards to any 'blend door' actuation

 

i do believe i have very low flow through core after testing with heat gun...   unsure if thermostat is stuck open (temp seems a bit low to me)

will be replacing thermostat and housing with the later version for possible access point for ether a mechanical or electric temp gage,

in some research, the control valve ( still closed system) is normally Open, allowing flow until AC is set, then closes off flow.

assume this is with vacuum on the valve, and it has none in normal state.

 

images or whatever of the blend door area location and maybe vacuum diagram of the control circuit

 

thanks in advance.

[pizzaman09]

The control valve has a pink plastic vacuum line running to it.  Might be worth checking to see if the valve is opened or closed.

 

It's also possible that your heater core is clogged.  They can be flushed out with some success.

[Ωhm]

[llhat]

thank you both,

 

is it possible to visually see the blend door actuator in the vehicle,  what needs to be removed to see it?

 

when is vacuum applied to underhood water valve,  on A/C selection, and this closes the water valve??

 

Once I get it inside on heated part of garage, I'll take my mity vac and apply some vacuum to water valve.

Seems the defrost door works and panel door works, as air changes direction on position of the selector.

 

am though leaning towards a core obstruction...

 

[89 MJ]

I’d also start with flushing the core, especially if the air does change direction. 

[llhat]

thanks.

will be part of process when i change out thermostat and 'new' housing. 

 

did a motorad 'kit' and coming from evay seller  (seller offer 50% off and free ship)

 

[gogmorgo]

Blend door movement is visible without taking anything apart. It’s under the dash above the passenger’s left foot. If you peak your head under the dash and slide the temperature lever back and forth you should see the cable moving a little bent rod, the other end of the rod is the blend door. I don’t recommend removing the cable from the rod unless you need to.

 

The valve changed at some point so I don’t know for sure if this is the rule, but I had a ‘92 XJ with almost no heat and patching a vacuum leak in the line down to the reservoir in the bumper brought the heat back. Which was nice cause I was road tripping it at -40 when I found and fixed the vacuum leak. But at any rate that would tell me the valve opens when it gets vacuum. The vent selector kinda worked prior to correcting the vacuum leak, but mostly only at idle.

[llhat]

confirmed there visual confirmation of the blend door operating...   the cable moves with the movement of the lever on dash and it is connected.

 

Today...

Drained coolant

Changed Thermostat  (192°)  I did drill a small vent in the flat surface of the thermostat and oriented it 'UP' on placement.

I used a Motorrad kit with an New housing, etc,   but for a later model year to get the threaded fitting so I could install a mechanical temperature gauge.

 

There was an issue,  needed a 3/8 npt male to 1/2 npt female bushing as without the bushing the probe on the gauge would not seat or seal, (Heck the retaining nut would not even start in the furnished adapter)

 

With coolant drained, I put some 'light' air pressure in the hose that is connected to the thermostat housing, (it feeds the control valve and then to the bottom fitting on the heater core.

I could hear gurgling of coolant leaving the heater core back to the block....

So...  'assumed' the core was clear.

 

Filled with 50/50 concentration ( from full strength jug)  and took my time to hopefully not air lock.

(the fitting on the thermostat housing actually looks higher than the temp sender at the back of the head),  so I filled until a trickle of coolant exposed itself.

 

Fired er up and waited for it to warm up.

 

did so and then also vented again at the housing fitting, got just a little burp.

 

Still NO heat,  and  I manually moved the lever on the coolant valve and that hose just did not heat.  Day or two ago, I unplugged the vacuum line from that valve and moved the lever and put my finger over the port, it did hold vacuum.  I also believe this valve is OPEN with NO vacuum.

 

so at some point  "someone" is gonna put a heater core in this thing... and I doubt it will be me.

 

in regards to the mechanical temp gauge, I think it will be 'off' just a bit because of its location,  I'll be monitoring it closely.  It did show 180, but i expected it to hit 190+....

 

shut it down,  next step will be check system cold for coolant level.

 

[gogmorgo]

Air pressure gurgling through something isn’t a particular good tell of whether or not a heater core is free and clear, or if a valve is operating correctly. Definitely not enough to commit to changing a heater core.
You can bypass the heater valve easily with some hose adapters. That’ll tell you whether or not it or the vacuum to it is the problem over the heater core. 

If your weather isn’t cooperating in a way that would let you run a garden hose through the heater to flush it out, you can usually get away with doing it at a wand wash, but be real ginger careful with 2000psi if you can’t get the tip off the pressure washer wand.

[llhat]

yes,  back thinking on this I 'should have' got my water hose to it to check flow... and not just that low air pressure. especially while i had the system broken and drained

 

I think i will succumb to the feelings and do a partial drain to do this,  hoping to get the hose connections off  at the core without breaking something...

know about taking a hook or something to break the 'seal' after removing the clamps instead of trying to jerk on those hoses..

 

I've got it in my 'wash pit' so water on floor not much of a problem...   KNOW this would be cheeper than just changing the core out...  figure it is a 50% proposition.

 

will resort to CLR or chemical something before pressure washer... agreeing on the 2000psi risk!

 

and it has warmed up here

[AZJeff]

Harbor Freight (among others) sell infrared temperature sensing “guns”that have a built in laser pointer.

 

Warm up your engine, and make sure the heater control valve is open to allow full coolant flow into the heater core.

 

Using the temperature gun I described above, point the laser at each of the two nipples of the heater core.  The difference between the inlet and outlet should be relatively small.  If one side is much lower than the other, that’s a clue that your heater core is plugged.

 

Whether flushing both directions will alleviate the low heat is totally dependent on what sort of crud is blocking the core🙁

[llhat]

^^^^  thank you

have one and have done that test, which initiated the thought of need to replace thermostat, as temp was a bit low.  (170's)

 

On these systems, that pesky coolant valve operation is the mystery... 

in some older posts it is indicated the valve is normally OPEN, allowing flow, 

when the A/C control is requested, supposedly vacuum is applied to that valve Closing it.... 

 

this is one of the things we've tried to confirm.

 

these lines are to the 1989 design with the crimped collars to seal the hose to the tubular fittings...

there are worm clamps at the core fittings, and to the top and bottom of the plastic tank on the firewall.

 

When I finished up work Thursday evening,  I could, by touch,  determine the core was not getting warm at all..

 

and agree on "IF" it can be flushed...   Like I indicated above when i had the system open/ drained,  there was Air Flow through the core,

and I could hear the coolant flowing to the fitting on the waterpump by the gurgling sound ...  and I did 'restrict' the amount of pressure on

the air gun..   it is a 'safety' gun that have two large bleed off ports to control pressure out the end of the device.