79 dodge b100 3.7 temp gauge never get over the minimum normal mark. mainly hovers in the colder side. I do not seem to be overheating. the van heat is at best warm. no matter how long i drive it for. i have half of the rad blocked off with cardboard, with having no affect. its getting cold here in pa and i would like some hot heat at my vents. i did replace the tstat. and had no change or affect

Dodge vans have a very very efficient cooling system. It is quite normal for the van to rarely reach even the middle of the gauge in hot temperatures when working hard.

I suspect your problem is in three areas:

(1) a clogged heater core
(2) worn out weatherstripping sealing the heater box to the firewall and sealing the various vents to each other
(3) possibly debris or misadjustment preventing the heater diverter door from blocking the cold air from entering the vents when you move the temperature slider to heat.

If your van does not have air conditioning, then it is fairly simple to completely disassemble the heater ducting and heater core housing, remove them from the van, flush the heater core, clean out the vent system, replace the worn out weatherstripping, and reassemble.

Several years ago my brother's 83 Dodge van (powered by a slant) had similar issues as you are having- poor heat output and the temp gauge never reached even the mid point. It had a new radiator, a tested good 195 degree thermostat, and the block and head had ben rebuilt, so I knew there were no problems in the main cooling system. In one evening i was able to completely remove the HVAC system from his van, clean it out, flush the heater core, replace all the worn out weather stripping, and reassemble. My brother's van now gets nice and toasty warm quickly, has much better airflow out the vents, and it still doesn't get the needle to the halfway point on the temp gauge.

The main problems I found with his van were the weatherstripping that sealed the system at various points was worn out and the heater core was partially clogged. I used standard grey self-adhesive weatherstripping from my local hardware store to replace the worn out factory weatherstripping.

My brother's van is a bare bones model with no AC and without even vents in the dash, so it was very simple, but even an A/C equipped van shouldn't be too hard to deal with.

I suggest starting by reverse flushing the heater core. Find the two hoses going to the heater core on the passenger side of the engine compartment and use a garden hose to flush it out. I would not be surprised if that is all you need to do to restore heat to the cab of the van. If that doesn't work then you will need to go in deeper.

A factory service manual will be a necessary tool for this operation so you can see how the vent systems all come apart and go back together.

You shouldn't need to block the radiator at all. That is a trick reserved for places where it gets really cold, like Alaska, where I grew up.

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Casually looking for a Clifford hyperpak intake for cheap.

You'll want to figure out how hot the heater hoses are getting. Run the engine until your thermostat just opens then turn the heater on. If heater is "barely warm" then (carefully) touch both heater hoses (or use a digital pyrometer). If both hoses are too hot to hold then something is wrong with the temp door or air seals in the heater box. If one hose is hot & the other is warm then there is a flow restriction- clogged core, bad AC shut-off valve (if equipped), air bound core, etc.

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63 Valiant Wagon
225 - 4 bbl

so i replaced the radiator cap and had my van sitting in the garage after work and while sitting there the heat got so much better. thought it was fixed. started driving then i noticed the air was just about warm. same as before. also while in the garage the temp was higher then the min normal mark but not in the middle. by the time i got home , the temp gauge was back at the minimum mark. now i did notice the heater hoses to be fairly hot both sides. so i am assuming that what suggestions i got were correct being the seals in the heater box are not sealing or leaking. i do not have a/c as well as bare bones vents. only defrost and floor vents. so what i am looking to do pull the box out from the dash and the engine apartment? any tricks i should know of?

I read your last post to suggest that the weatherstripping and seals in the vent/heat system are deteriorated and leaking but that your heater core is not clogged. The hoses being hot on either side of the heater core suggests you have flow through the core as does the fact that you did get some heat from the system while in a protected garage. The fact that the air coming out of the vents got cooler once you were out of the garage and moving suggests that the weatherstripping sealing the vent system to the body of the van has failed and cold air is bowing into the vents where it shouldn't. This was exactly the problem with my brother's van.

Give me a bit and I will post the instructions on how to remove the heater system from the factory service manual.

The temp gauge on my brother's van always run very cool even with a 195 degree thermostat and a thermostatically controlled clutch fan in it. The cooling system on the Dodge vans is very efficient.

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Casually looking for a Clifford hyperpak intake for cheap.

Reed: I agree, however air flow thru heater core can be blocked by copious amounts of crap sucked in through cowl over the years; leaves, dirt, critter nests and trash. When I rebuilt My Dart's heater, the core chamber was half full of composted leaves and leaked coolant, and every seal & gasket remnant still clinging was degraded, brittle, and unable to seal.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

wjajr is right- debris can get sucked into the heater box, but the design of the vent system in the vans is much less prone to debris buildup than is the heater box on a-bodies. When I pulled my brother's 83 van system apart there was actually very little debris, and he parks it under trees at his house without a cover.

I will try and get the heater diagrams posted today.

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Casually looking for a Clifford hyperpak intake for cheap.

Here are the scans of the 1983 Dodge van factory service manual section dealing with the heater system. As you will see, it is very simple to remove the entire assembly from the van to clean and reseal it. Another possible cause of the no heat condition could be that your control cable(s) is/are misadjusted, but this is less likely.

If you click on these pictures they will open up larger in a new page. Get a few rolls of the self-adhesive foam weatherstrip (not too thick- I think I used 1/2 inch thick, maybe 3/8), some rags and rubbing alcohol to clean all the mounting surfaces for the weatherstrip, and maybe an exacto blade to clean any stubborn weather strip off. I would go ahead and flush the heater core while you have it all apart, just to be sure it is clear and since you will be in there anyway.

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Casually looking for a Clifford hyperpak intake for cheap.