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HEAT control switch....

XpedientJ

XpedientJ

NAXJA Forum User
Location
MA
'99 XJ:

- Fresh radiator, relatively-recent H-core/'stat/Hessco pump and housing, etc.

- With some past intermittency, heat output is now consistent, but...just
not as hot as I would think it should be. I don't expect it to be blazing,
as with the stock radiator, and the operating temps it yielded, but...
again, just not HOT.

Supply/return hoses are both hot, equally-so. I don't think there is any
air-bound condition, at this point...

Thus, wish to confirm that the dash heater control switch is giving max
hot, as it should. I note that there are just two wires serving it; thus,
WOULD it be a proper test, to just jump those two wires to simulate
the MAX position, or...is there another/better way?
 
You should measure the temp coming out of the center vent to at least get a baseline. Plus we can tell you if that is normal. Hot and cold are sort of relative terms. If you're married, you'll know exactly what I mean.
 
There has been some talk that aftermarket heater cores do not make the "heat" that the genuine Jeep heater cores do. I have not personally tried the aftermarket heater cores. Last time I did an evap I replaced the heater core as preventative with one from the Jeep dealer. As long as you know the blend door is seated properly and moving, you can remove the controller for it and turn it with a pair of pliers. As others have mentioned, what thermostat and what is the engine operating temperature?
 
i recently had the same issue mine was a partly clogged heater core. but on my 1988 with the fan on 2 i get around 150*~160* before i would get about 120* which didnt feel hot at all.
 
- Haven't found a thermometer to advise actual temp output....

- Running the requisite/OE 195 stat

- Did just find that the output max temp doesn't vary much, if at all, with the temp switch at min or max...AND, then noted a brown wire, coming from the flat, gray 7-place (but, just six wires servicing) connector...is loose, and was rather obviously grouped with another, or others, in one of the twist-connector groups there.

Looks like, perhaps, it is the one with a light-gray wire, and a dark-gray wire, both having a black stripe? Can anyone advise WHERE/with what this brown wire should be coupled?


Thanks, indeed....

{Also, my recall from the core replacement isn't strong: Where may I access the blend-door controller?}
 
That's a real rats nest of wires, even worse than my 84 CJ-7. One might suppose that the two single wires should be joined.

Have you back flushed the heater core ? I just back flushed the core on my 98 and heater output is double or triple. It was 3° this morning and the drive to work was chilly, the drive home was toasty.
 
NO, what appears to be a single adjacent wire, is the two gray wires mentioned...

Just the factory....'nest', then....!

Not too many miles, and two years, since the core was replaced.
 
Why all the wire twistys ? Did somebody named Bubba wire in a heater control from a different model year XJ ? By the way, twistys are used for household wiring and should not be used for automotive wring.
I quickly loose patience when dealing with wire diagrams, I would just find the correct controller switch ( or even the entire switch panel ) with the correct wire colors and then you can just match up the same/same wire colors.
 
XpedientJ said:
Looks like, perhaps, it is the one with a light-gray wire, and a dark-gray wire, both having a black stripe? Can anyone advise WHERE/with what this brown wire should be coupled?

Click to expand...
Pretty sure the brown wire goes to the rear defrost (coupled to a controller that turns it on separate from the switch when you select front defrost). Not sure if the '99 had that option, the earlier years did. It was a 12 gauge brown wire, the only brown wire, which is why I think that's what that wire is.

XpedientJ said:
Supply/return hoses are both hot, equally-so.
Click to expand...
This makes me think you have a partially clogged heater core.
 
If it help, here's a schematic for the Blend-Air Door control and a view of the back of the HVAC control panel with connector pin outs.

jpgBlendDoorDiagram21_24_13.jpg

.
ClimateControlPanel.jpg
'.
.
The door actuator motor intermediate drive shaft should turn about 90 degrees stop-to-stop when turning the temp control knob from full hot to full cold. Key to RUN.
 
My 99 has cold heat as well, heater core horses are both the same temp, heat control knob moves the servo, the door is in the closed position when the servo is on the hot setting

Engine temp about 200, hear coming from center vent is maybe 120

What other blend door would let cool air inside of the cabin
 
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