1991 Caravan Heating Problem

I have a 1991 Dodge Caravan, 3.3 liter.

I have had this for about a year now. I recently flushed out the whole cooling system and added new coolant for the winter. I dont seem to get any kind of circulation for the heater core. I have replaced the thermostat. I have switched the hoses going to the heater core thinking they were hooked up backwards, but no luck.

What it is doing is, as long as I dont turn the heater fan on there is hot air coming from the vents and all, but as soon as I turn on the heater fan, it starts blowing cool air and if I turn the fan on high it will blow cold air. It is like the fan cools down the water going through the core.

I take the radiator cap off and it does not seem like there is much circulation going through the radiator. Once in a while I can feel the hoses at the heater core and they are both hot and then at times one is hot and the other cool.

Is their anyone out there that has had this problem and knows a fix, as it is now getting winter and my wife wants heat. I did not have this van last winter so I do not know if it worked before I got it or not.

Thanks for any help. Bob

I have a 1991 Dodge Caravan, 3.3 liter.

I have had this for about a year now. I recently flushed out the whole cooling system and added new coolant for the winter. I dont seem to get any kind of circulation for the heater core. I have replaced the thermostat. I have switched the hoses going to the heater core thinking they were hooked up backwards, but no luck.

What it is doing is, as long as I dont turn the heater fan on there is hot air coming from the vents and all, but as soon as I turn on the heater fan, it starts blowing cool air and if I turn the fan on high it will blow cold air. It is like the fan cools down the water going through the core.

I take the radiator cap off and it does not seem like there is much circulation going through the radiator. Once in a while I can feel the hoses at the heater core and they are both hot and then at times one is hot and the other cool.

Is their anyone out there that has had this problem and knows a fix, as it is now getting winter and my wife wants heat. I did not have this van last winter so I do not know if it worked before I got it or not.

Thanks for any help. Bob

It's been a while since I drove a 91, are the doors that direct the air behind the dash operated by vacuum or cables?
If they are vacuum then perhaps they are sticking.
Another possibility by your description is there is air trapped in the system. I got the air out of mine this way.
Park the car facing slightly uphill, remove the radiator cap, let the motor warm up until the coolant starts to circulate then raise the idle for a few minutes, adding coolant if the level drops. Replace the cap and let run for a while. Also make sure the overflow bottle is full.

Yea, i have checked the controls and they are working fine. I have tried all that to get the air bubbles out also.

I have pretty much decided that it is the heater core partially clogged, but it is quit a chore to replace.

So, the next question is, I heard from someone else, to try and unclog without taking out or replacing the core. That I should fill the heater core with distilled vinegar and let sit for about 24 hours and then reflush out the core.

Has anyone heard of that as a solution?

I did flush out the heater core again yesterday, and now I do get some heat at high RPM, but at idle there still is no circulation.

It is about a 4-5 hour job to replace the core and it is in the teens and below for temp. and I have no garage, only work outside, so am trying anything to fix the easy way.

Thanks for all your help.

A few weeks ago I had trouble clearing a shower drain, my wife gave me a jar of white vinegar. I poured it in, let it sit for 1/2 hour and flushed with hot water. It worked great. Perhaps you could also try to blow it out with a air hose.