No heat in my 95 RMW!

Hello all...
i know this issue has been discussed before, but I thought that perhaps there's something I might have missed.
I have flushed the heater core, backwards and forward several times, changed to a new 180 degree thermostat and still the car runs at about 170 degrees and there is cold air blowing even with the control set at top limit(90 degrees).The air works fine and is ice cold, but there just is no heat! Is there something i'm overlooking...a control relay, or switch or something that determines sending heat into the passenger compartment? Also, both heater hoses are very hot,so I assume that heat is going through the core. Really has me stumped! Any clues i might try?
I thought this might be a design flaw, since my first RMW did the same thing !! HELP!

dnvrdisc wrote:

Hello all...
i know this issue has been discussed before, but I thought that perhaps there's something I might have missed.
I have flushed the heater core, backwards and forward several times, changed to a new 180 degree thermostat and still the car runs at about 170 degrees and there is cold air blowing even with the control set at top limit(90 degrees).The air works fine and is ice cold, but there just is no heat! Is there something i'm overlooking...a control relay, or switch or something that determines sending heat into the passenger compartment? Also, both heater hoses are very hot,so I assume that heat is going through the core. Really has me stumped! Any clues i might try?
I thought this might be a design flaw, since my first RMW did the same thing !! HELP!

How did you fix your first rmw?

there is a door in the heater box that closes off the core,. it;s not moving
for whatever reason,...

To answer your first question....I took the first RMW to a Chevrolet dealer and paid a large sum(plus many trips!) to get it working so that I have enough heat to keep from freezing in the Colorado winters. I'd like to try to fix this one myself, since I can't afford the dealers prices for repairs that they are pretty vague about telling you what they did!! Guess they might all be like that?
Bob

Disconnect the battery for a few minutes then reconnect. Turn the ignition on and let the climate control recalibrate itself, you might be able to hear the blend door move while this is happening. 91-93 will have a countdown on the display, 94-96 won't show anything. Don't touch it while this is happening. Once it's done the blower will come on.
Had this happen on my car a couple times, the computer gets stupid and doesn't know what position the door is in.

The lack of heat on my '95 RMW is a little different. It heats as it should intermittently. When it's not heating, if I grab the inlet hose to the heater core, it is hot. The outlet hose is cold. This tells me there is insufficient flow through the core.

I've removed the hoses and found I can blow through the core by blowing into the inlet hose with my mouth. Also can blow back into the hose to the water pump housing fairly easily--both the inlet and outlet hoses.

What is the function of the plastic device in the inlet hose? It has an arrow labeled "heater core" on it. Is this a check valve or is it a flow restrictor?

You need to flush the core, one way, then the other. Blowing into it doesn't tell you anything.

Tom

I needed this post today! Both the Roadmaster and the OCC are down do to heat! I saw the countdown with the OCC several times but the fan didnt kick in. What peeves me,is I had the Roadys core flushed in August,so this wouldnt happen! Arrrrrggghhhh! I usually dont drive either one during the winter,but I loaned my winter ride to a family member who needed some help. To top things off,the Roady keeps freezing up the glass on the inside of the windshield,making a hell of mess on the dash matt. Rant over...

Does your fan in the OCC run at any time? My OCC does not even have the compressor hooked up, or the compressor hoses installed, and the fan will run when the countdown is finished. If the fan does not run, it could be the fan, or the controller.

Fan runs fine. If the heater puts out heat, the fan will modulate from full on to two bars. If the heater puts out cool air, the fan will stay on full bars at all times.

As I said, when working normally, the inlet howe to the core is hot, the outlet one warm. When it doesn't heat, the outlet hose is cold.

One of the B-bodies I owned had a lot of the clumps of the original GM stop-leak lurking in the system, and every so often one of them would end up in the heater core or restrictor. So I just flushed it out, and again I had heat. I'd just disconnect the hoses from the water pump and force a garden hose against each one for awhile until it flowed clear.

Well, there are really only three reasons why you wouldn't get heat in these cars:

1: No coolant flow through the heater core (or coolant itself is cold)

2: Blend door is stuck in cold air mode

3: Fan isn't moving air

Has anybody had the issue of..... when you put it on heater it blows out the defrost and visa versa? Mine does that and driving back and forth to Burlington is getting colder. And it isn't a strong flow of air either?

Assuming blend door and if so what am I looking for. I don't want to start tearing things apart looking for issue only finding myself chasing it. I would love to know exactly what i'm looking for. Thanks. I have limited amount of time to work on it when i'm home, since i'm constantly gone lately.

Has it always been this way? It could be that someone worked on it, and the vacuum lines are hooked up incorrectly.

The blue hose (first position) goes to the defroster valve, and is next to the violet hose on the end of the manifold. The tan hose in the third position between the red hose and the orange hose.

You could check to make sure the vacuum is being ported properly. If not, it could be the manifold, or the signal it is getting from the control head.

Thanks and yes it's been like this for awhile. The heat has been gradually going away so assuming heater needs flushing.

With the two functions occurring out of sync with the settings you have a different issue to address. The heater core may well need flushing, but the defrost working in heat, and vice versa, you need to address that as well.

That I know. Thanks

Just an idea, in the summers sometimes I have to run my climate control to full-hot and the back to full-cold, changing the temp, to get the a/c really super-cold. I think sometimes a door in there hangs up a bit and doing the full-cycle from hot-to-cold a few times gets it back to where it needs to be. You might try that.

Also, I HIGHLY recommend flushing all the red coolant out if you have it and replacing it with new "any-color-compatible" coolant. I know they say it's gotten better, but I hate Dex-Cool coolant.

-Mike

Well I went with putting in a new heater core and just left the controls alone. The best 2 hours I spent. Now the heater will blast you outta there.

Sometimes the heater core is not salvageable, and you just have to replace it.

Replacing the heater core is your best bet. I flushed mine, backflushed , results were mediocre. Changing the core out was not that hard.

I flushed it and the heater now works fine.

I tried the recalibrate the flap without much expectation. It worked!
Thanks!

Isurf wrote:

I tried the recalibrate the flap without much expectation. It worked!
Thanks!

Sometimes the simple solutions work! Good Deal!

Must....contain... inner.... teenage ....boy....arrrrrrrrrrrrgh! Various oral manipulations of the heater core here are not making this easy.

last year the recalibrate got me reasonable heat. This year I flushed the heater core and got better heat. Thanks for all the help.

I did a heater core flush on the wife's wagon today. I disconnected the heater hoses from the Tee and the restrictor. Then I just held the garden hose to each end for a bit, flushing in both directions till the water was clear. I folded the hose to control the volume and pressure. Wife says the heat is much better now!

I really need to do a complete system flush. I drained and changed the coolant and hoses and cleaned/flushed out the tank before putting the car back on the road, but the coolant is now pretty dirty again.

Hopefully the core flush gets her through the winter...

rcktpwrd wrote:

I did a heater core flush on the wife's wagon today. I disconnected the heater hoses from the Tee and the restrictor. Then I just held the garden hose to each end for a bit, flushing in both directions till the water was clear. I folded the hose to control the volume and pressure. Wife says the heat is much better now!

I really need to do a complete system flush. I drained and changed the coolant and hoses and cleaned/flushed out the tank before putting the car back on the road, but the coolant is now pretty dirty again.

Hopefully the core flush gets her through the winter...

Have to pull the Knock Sensors and flush all of the junk out of the block.