Medic Andy

I turned my heater on my 1995 LT1 on last night with the outside temperatures around 38F, and nothing, no heat, the ventilation system was only blowing cold air. I looked at a couple of youTube videos about this topic, and a dirty / clogged heater coil could possibly be the issue. My bad, but I have not checked the cooling fluid since my car got some mechanical upgrades like a CompCam and an electric water pump about five years ago.

So I checked the antifreeze fluid, and it looked brownish...... I then disconnected the heater coils water in & out water supply hoses and connected my garden water hose to the cooler "water out" hose. I then opened the garden hose faucet slowly, and there was lots of larger and smaller trash pieces being flushed out from the heater coil.

I didn't have enough time to flush the entire cooling system today, but this issue will be addressed soon! I will buy me a cooling system flush / cleaner, which should take care of the trash particles.

Either way, I started the car again with the gauge showing 120F, and the ventilation temperature set at 90F (felt by hand) was cold. I then took my car out for a ride until the engine temperature was up at around 186F, which is as hot at my car's engine will go. (The electronic water pump is controlled by the computer system, and the engine temp was set to 182F before the thermostat opens by the performance shop who did the upgrades about five years ago). The air coming out of the vents was still cold. I then noticed that the dash heating & cooling controls seem not to work correctly, since the air would only blow out on the front windshield's defrost vents on top of the dash while the engine is turned off. I pushed every control setting from the "Auto" push button to the defrost button, but nothing changed the air flow, the only vent working was the defrost vent on top of the dash.

I then turned the engine on, and the heating / cooling controls started to work according to what the individual button pushed requested. The only button that didn't work was the "Air recirculation" one. The light would come on when pushed, but would turn off again within a second of letting go. I also noticed that the engine barked down not only when the Auto / AC was selected, but also when I pushed the "Air Center / Air Feet" button. All other buttons worked as shown on their picture.

I then unplugged many electrical connectors which I assumed are controlling the AC / Heating system. To my surprise, the air now coming out of the vets was nice and warm. I took the Corvette back on a short ride, and the heat stayed warm. I then pushed the temperature selection button until the temp indicated was 60F. The air was blowing very cold, so the temperature selector seemed to work when dialing the temp down. I then raised the heat back up to 90F, but the temperature really never got as warm as it did before cooling the system down.

There also is a "I believe" vacuum control unit installed above the drivers feet area / somewhere under the steering wheel, which was replaced in my car with a "used unit" about also five years ago. I had to replace that unit since the main Heating / AC control unit in the dash stopped responding all together.

So now I'm a little stuck and I could use some feedback on where to go from here. For all I know, the dirty antifreeze cooling could be still to blame, since me disturbing the cooling systems interior when I drained some of the fluids out could possibly loosened more larger particles which clogged the heating coil again? As stated earlier, this issue will be taken care off after I add some cooling flush and clean the system out.

I'm still a little stuck on the heating / cooling dash mounted controller doing different things depending if the engine is running or not. I wonder if the AC / Heater unit or the vacuum unit mounted above the drivers feet, which I previously replaced, could be going out again?

Has anybody ever experienced the issues that my car is having? Any feedback or recommendations are greatly appreciated!

Andy

kenmohr

Pull all components and send to Batee. Call first and ask what to send.

fake

Had the same problem heater core went bad from not servicing the cooling system . Cost me three days of hard work and a couple hundred for parts. I would check your motor you probably added a lot of stress to it. Cam bearings get to hot ,a lot of friction. GM recomends use no chemical flushes except water. Get the service manual if you have not yet!

Medic Andy

Who is Batee, and how would I get up with him or her?

Andy

Mr. Peabody

Go here: http://batee.com/?gclid=EAIaIQobChMI...SAAEgJ2X_D_BwE

They have a very good reputation.

pcolt94

Before you start taking the car apart and sending parts out arbitrarily, there are a couple of checks that you can do.

After the engine is at operating temperature, check to see if the heater hoses are about the same temperature as the larger radiator hoses. Your hands can tell the difference if there is a big difference.

You also have to look at the blend door to see if it is moving. Remove the blower motor control unit from the top of the evaporator box. Then turn key on, place fan to lowest setting and have someone run the temperature from 60 to 90 a couple of times and see if door moves about 90 deg from side to side. Just look in the evaporator box with a flashlight.

If the control head seems to work OK and the door does not move correctly, then it's a possibility the door motor might be the problem.

kenmohr

Definitely check as stated above. But send all three parts. I was not going to send programmer back, just blend door motor and programmer, Blend door motor was OK the other two needed rebuilt.

Medic Andy

I decided to add a cooling system cleaner (Prestone) to my dirty antifreeze just to see if something would happen, and it did. I drove for about 45 minutes with the cleaner added, and I noticed that the temperature started to go up from blowing ice cold to warm about thirty minutes into the drive. The cooling temp was right at 185F, which would be normal for my car. The heat blowing out of the vent after 45 minutes of drive time was not hot, but definitely warm without cooling off or cutting off at random. I had the vette then sitting in the garage for the last three days with the cleaner and the dirty antifreeze still in the system. I took her back out on a drive for about another 45 minutes, and the heat blowing out of the vent is even a little warmer now.

So here are my thought, but I would like to run them by you guys first..........

What would happen, assuming that I get lucky and the heater coil was clogged, if I were to reverse the cooling in / out hoses to the coil and leave them reversed? I was wondering if reversing the water flow could possibly help with breaking up any trash that may still be stuck in the coils fins while I'm flushing the engine / old cooling fluid? I am planning on flushing the cooling system on Sunday. I'm planning on draining the old antifreeze and flushing the system until the water drained is clear and free of any trash particles.

I will then add green ethylene glycol Prestone antifreeze (I called Prestone, and the fluid I bought is 100% compatible with the orange Dexcool that I think GM recommends?), and mix it as required (1:1) with distilled water.

So, two questions......

1) Would it hurt reversing the water flow going into and coming out of the heater coil and leaving them reversed, or could I damage anything by doing so?

2) Would it be ok to add a cooling system cleaner to the new antifreeze fluid and just leave it in there until the next time that I'm going to flush the cooling system again, maybe in two years from now? The Prestone cleaner is not suppose to harm any type of seals, gaskets, rubbers, or aluminum.

Any feedback are greatly appreciated!

Andy

ctmccloskey

Hello Andy,

I am not sure about reverse flowing the heater core in your LT1 Corvette. I don't know about the C4 but on my 1968 C3 the heater core uses two different size tubes which would make it harder to reverse. I still have a Prestone "Flush and Fill Kit" mounted on my 1988 C4 and still use it when flushing the engine. I like it because I have a hose to put the old anti-freeze into a bucket so it can be disposed properly. Green anti-freeze will kill any animal that drinks it, it smells "good" and is inviting. Please dispose of the old coolant properly in your area.
Using Radiator cleaning materials in the car for two years is not something I would do. The cleaning agents might do damage if left inside the cooling system too long. Especially if you have the plastic tanks on the radiator.

How long was the old coolant left in the car? You said it was the red Dexcool that came out of it.

Where you are you might not have to use the standard 50/50 mixture of antifreeze and distilled water. I live north of you in the Washington D.C. area and I have been using a 70% water 30% AF for decades with no ill effects on my L98 as I don't drive it much in the winter. 50/50 is for places that are colder than what we see in our part of the country. If where you are it does get below zero F then I might re-consider. The coldest I have ever seen in Northern Virginia was -5* F and that was very unusual. I spent one winter in Syracuse, NY and there you clearly need a minimum of 50/50 as it is cold up there.

Good Luck with your radiator!

Chris a.k.a. ctmccloskey

Medic Andy

Thanks for your reply Chris,

I had a CompCam and some other engine work done about five years ago, so that would have been the last time that the cooling fluid was changed. I would however assume that the cooling coil was not flushed during that time. And if I'm fully truthful, I changed the coolant fluid out about ten years ago, and I didn't flush the cooling coil back then either. I didn't even know that this was something that needed to be done..........

Either way, I know it now....

I bought 20 gallons (to flush the Corvette and my trucks cooling system) of distilled water from Target today at a cost of $0.69 a gallon, so I will flush the Corvette's cooling system a couple of times with the distilled water and some additional cooling flush / cleaner tomorrow and then fill her cooling system up with the Preston antifreeze / distilled water mix to hopefully finish this task with the heater working again.

I have four 5 gallon plastic buckets ready to hold the old cooling fluid. We have a local County dump which takes any fluids or chemicals at no charge, so this is a great service that our County offers to us residents!

I will let you know tomorrow if flushing the system, and especially the heater coil resulted in hopefully a again fully functioning and working heating system.

Best regards,

Andy

Medic Andy

I purged the cooling system several times with distilled water total before finally refilling the system with coolant. The heater pumped really hot air out, so I'm pretty sure that the heater coil is hopefully still good. A lot of brown water with lots of "I assume" rust particles and black / brownish flacking particles, some were the size of 1/4" in diameter flushed out of the cooling system.

But, not all is well yet! I noticed that the heater controls work as they should. I started the engine while the car was parked, and lots of hot air came out of the vents with the heat setting at 90F. I then cut the heat down to 80F and the temperature gone down a little, the same happened again at 70F, and the air was blowing cold at 60F. The outside temp was 45F while I worked on my car. I then repeated the temp settings by raising and lowering the heater settings, and the system responded perfectly.

I then shifted in 1st gear and started to drive down the road, and the heater worked fine. I pulled onto a country road, and I kept the rpms down while shifting up until I was in 5th gear, and the heater worked great. The air was at the 90F setting so hot that I rolled the windows down. I came to a stop and took off again, but this time I pulled the rpm's to around 4k, and I noticed really fast that the heat cooled off a lot. I would think that the temp lowered itself by about 90%, and the temp now coming out of the vent was just barely higher then the outside temp. I then turned the engine off again and started driving at lower rpm's again, with the heat working, but the heat turned cold about three miles down the street. So it seems that the heat sometimes stays on, or turns off, but there does not seem to be any reasoning on why the system is doing what it's doing.



I then stopped my car and cut the engine off. I waited about twenty seconds and restarted the engine, and lots of hot air was coming back out of the heating vents. I then took off at lower rpm's, and the heat stayed warm, but the heater would stop again with blowing hot air as soon as I raised the rpms. I cut the engine off five times during a twenty minute drive, and the outcome was always the same. The heater and all heater functions would work great when stationary or driving at low rpms, but the heater turned cold every time I gave a little gas and raised the rpms.

I also noticed that the hose leading into the coil and the hose leaving the coil are very hot when the heater is working, but the hose out is definitely cooler to the touch when the heat is not working.

I was also wondering if the thermostat may be bad or that the electronic water pump may be to blame, but the heat always working, regardless if the engine is warm or cold at engine startup, seems to remove the thermostat or water pump as possible issues.

Maybe I have a vacuum issue? I looked for some possible disconnected or damaged vacuum lines, but I was not able to find any.

I added another dose of cooling system flush / cleaner into the antifreeze to give my car another good flush before I'm replacing the cooling fluid one more time on my next day off from work in two weeks, but I'm hopeful that the heater coil is still ok........

So now I need to find out on why the heater door is closing when I'm raising the engines rpms as I start driving down the road.

Does anybody have any thoughts on what I should try out next?

Andy

Medic Andy

I flushed the cooling system out one more time today, and replaced the thermometer and the original old radiator cap. I then took her out for an hour ride, and the heat worked perfectly, for most of the time....... The heat got cooler, still warm, just not hot a couple of times after I hit the gas paddle and got the rpms up a little. But, the heat never turned cold and although the temp got cooler at times, it always turned hot again after a couple of seconds.

I have no issues leaving the heater as is, but I will check the vacuum system to see if there possibly is a leak somewhere. I could be wrong, but I would think that the heater coil is ok, since the heat is working. I would also think that the gear mechanisms for the heater door is probably not stripped, since I can raise and lower the temp settings, and the system responds to the temperature control settings.

It would be great if someone could point me toward the location of the vacuum hoses and connections which operate the heater door. I looked around, but I was not able to locate them.

Thanks again for all of the great feedback you guys gave me!

Andy

3D-Aircrew

Bryan did a beautiful job on my Atari dash for my 1986 over the holidays. Replaced an LCD panel, power supply and the connector set. Sent me the old parts back with it. If you are so inclined you can make the repairs yourself with parts purchased from Batee and use dozens of informative repair videos from:

Batee Online Repair Videos

pacoW

had very similar issues to yours in my '96, I did this and it fixed it. Maybe you can try if you are mechanically inclined and have the time.

pcolt94

Normal operation of the heat is something to be desired as one would think as it should work. This is how my 94 operates and has been discussed on the Forum but not wide spread.

Say I set 72, I get good heat for a while then it goes cool (not really warm). So I bump it up to 74, same thing happens. When I want to keep some heat going and get to 85, that’s a high as you can go with regulation. I have noticed at 85 (or some other temperatures) if you just leave it there it might go warm again but it may take a while and you may be cold for awhile.

When you set 90, full heat is on and will blow full hot all the time. After some time it's too hot and I have to lower it and it becomes a manual back and forth operation.

I might run floor heat occasionally. But here in FL with lots of moisture I get my heat in recirculation or Bi-level mode, works for me, depends where you live.

In my opinion, the temperature regulation is just not very good with the electronics trying to set the blend door in a good position. This is just the way it works and I think a modification or re-design would be necessary to have better control of the temperature.

**There is no vacuum operation of the blend door, its electric. Only the vents are vacuum operated with vacuum solenoids in the programmer.

Medic Andy

Thanks for letting me know about this video! This is something I will most definitely do to my unit, which will hopefully take care of the issues that climate control unit has, which are identical to what the video repair guy is talking about with buttons not doing what you want them to do!

Thanks again,

Andy

Medic Andy

Thanks for your reply, this and the cleaning instruction of the Climate Controller will hopefully get my heating and electrical issues with the Climate Control unit sorted out!

Andy

kenmohr

Call Brian at Batee. He will tell you what parts go wrong on a experience basis. I was doing to send him the blend door motor and controller (my vents all worked fine ) and he recommended me to send the programmer as well. Sure enough the motor was fine had to rebuild the programmer and control unit. He does this for a living, trust him.

9T3VETTE