1991 Dodge Cavaran NO HEAT

I have a 91 Dodge Caravan and cannot get any heat. Engine runs great,
coolant levels are good, new thermostat, just no heat. I just got the
vehicle and found there was no thermostat, I thought that may have been
the problem. NOT! There is a 4 way valve and when the inside temp
control is moved the valve appears to operate. The water going into the
heater core appears to be hotter then the return water. Any
suggestions?

 

Core could be clogged

 

I also noticed the AC unit cycles even though the AC is not on. It
appears that the AC is over riding the heat. I disconnected the power
to the compressor. Still no heat however but is not really cold now,
kind of luke warm air.

 

Make sure that the blend air door is working. The door will seize and the
cable will actually slide at the control making it seem like the door is
moving but it is not. When you slide the temp control you should hear the
door hit the stops. The water valve under the hood is used for A/C. it shuts
the water off in the max cold position.

Glenn Beasley
Chrysler Tech

 

Glen,

I checked the blend air door and it appears to be working, When I slide
the control the air temp changes from cold when on the blue to just a
bit warm on the red. I think the door is hitting the stops.

 

Then I would suspect a stopped up heater core.
Especially since you said it was hot going in and warm going out
Glenn

 

Glen,

Tomorrow I'll pull the connectors from the heater core. I'll see if I
can run some water through the heater core with a garden hose. I'll
have to rigg up some kind of connector.

 

Glen,

Tomorrow I'll pull the connectors from the heater core. I'll see if I
can run some water through the heater core with a garden hose. I'll
have to rigg up some kind of connector.

 

clogged heater core?????

 

undo the hoses then have someone start it quickly while the hoses off and
see which line is the return hose and flush it that way so if there is any large
blockage at the intake side it will get blown out by the garden pressure and not
forced into the heater core deeper

 

Great idea! I'll give you an update tomorrow.

 

I made some connectors and was able to flush the complete system. The
heater
core did spit out some gunk. I refilled the coolant, just water for
now and I'm
actually getting some heat. Not what I would expect, I'm not sue if
when I
drain some water and add anti freeze if that will change things.

One thing that does not appear to be correct is the AC compressor kicks
in and
out when the heat is on. The line actually get freezing cold. It'slike
th Ac is
overriding the heat. I disconnected the AC via the two electrical
connectors
and the temp goes up. Still not what I would like but acceptable. Is
there
something else I may be missing?

 

The A/C will turn on if the panel is set to defrost. This is normal

Glenn

 

if the ac cylces while the defrost is on then it's working correctly it is suppose to
remove moisture form the cabin and uses the ac to do so
if it runs when the heat is on full heat then u have a issue

 

Some. It would be more useful if you put a thermometer on it and
told us what you were getting from the duct. Water boils at a lower
temp than coolant and cannot carry as much heat as a result.

Ted

 

There are some gains and some losses of pure water over water/entifreeze
mix. Ignoring the boiling point, pure water will actually cool better
(not sure if it's due to better conduction or higher specific heat
capacity), but the lower boiling point is a minus of pure water if the
temperature does get higher (but it may stay cooler due to the better
cooling). The net overall effect would depend on the engine and
conditions. Some people in racing actually try to eliminate or minimize
the amount of antifreeze for this reason (also there are products like
Water Wetter™). (Not arguing against using antifreeze - it prevents
corrosion and lubricates the water pump - and as you say raise the
boiling point.)

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

1995 Dodge Caravan here and am also experiencing the same problems as
everybody else here and then some.

The heater does not seem to get hot anymore. It simply blows luke warm
air if that.

I also have the problem of the air "magically" disappearing and
coming out of the windshield vents. Even when it shifts over to that
area, it hardly comes out.

When I get on the gas and the A/C is on the air stops coming out of the
front vents and shifts up to the top vents on the dash too.

My concern now is getting the heater to work again. I have noticed that
when I leave for work around 7AM it is about 36* outside and the heater
NEVER gets warm. However, if I am driving home and it is in the 60-80*
range the heater will spill out some heat, but not like it did in the
past.

I am going to have my mech replace the thermostat and go from there.

Also, has anybody figured out how to fix the magic changing of the
airflow?

 

The magic fix is to have the check valve at the brake booster replaced, the
one that controls the little black vacuum hose.
Your thermostat will more then likely fix your heater problem

Glenn Beasley
Chrysler Tech