coolwind57 Posted December 28, 2017 Share Posted December 28, 2017 I've been searching around for this specific symptom throughout the morning but hadn't found much on this yet. I have moderately good heat when I switch to "VENT" but absolute cold air directed to the foot wells at "HEAT". Other than that, "Defrost" mode works ok as well as my AC. I did read that vacuum issues usually give the tell-tale sign of all selections routing to "Defrost" mode but nothing on VENT and HEAT. Man, I need some dang heat! A couple of Months ago, I had only removed my heater valve junk and reverse-flowed my heater core and have done nothing since. Didn't have much need for heat till now. Anything jump out as I work on my system this weekend? Just a side note: This weekend, I'm converting to an open system, retaining my stock radiator, installing in-line filler neck on radiator hose, running 97+ heater hoses and installing recovery bottle. Popping in a new thermostat while I'm at it. I hope this helps with generating more heat, but there seems to be something going on with my controls on VENT and HEAT. Appreciate any enlightening. Link to comment Share on other sites More sharing options...
cruiser54 Posted December 29, 2017 Share Posted December 29, 2017 Before you do the work, see if both heater hoses are the same temp at the firewall. Also, there is a blend air door that controls cabin heat. Make sure it's opening. Link to comment Share on other sites More sharing options...
coolwind57 Posted December 29, 2017 Author Share Posted December 29, 2017 Gee I feel dumb. Looks like my issue was simply low coolant. Filled her back up and heat is good now at HEAT setting as well as VENT. Still kind of weird that I got some heat from one but not the other. I'm now a bit worried about how I lost that coolant, but I'm going forward with my closed to open conversion tomorrow. Link to comment Share on other sites More sharing options...
HOrnbrod Posted December 29, 2017 Share Posted December 29, 2017 5 hours ago, cruiser54 said: What's that 10A fuse hanging there? A Renix thing? Link to comment Share on other sites More sharing options...
Minuit Posted December 29, 2017 Share Posted December 29, 2017 TCU I think. 11 minutes ago, HOrnbrod said: What's that 10A fuse hanging there? A Renix thing? Link to comment Share on other sites More sharing options...
HOrnbrod Posted December 29, 2017 Share Posted December 29, 2017 22 minutes ago, Minuit said: TCU I think. That's it - forgot that. The HO TCU fuse is in the PDC under the hood.. Link to comment Share on other sites More sharing options...
cruiser54 Posted December 30, 2017 Share Posted December 30, 2017 You got it!! Link to comment Share on other sites More sharing options...
coolwind57 Posted January 2, 2018 Author Share Posted January 2, 2018 I spoke too soon. My problem is back. Wife and I nearly froze on the way to work this morning. As previously mentioned, adding coolant helped a bit. But.... I proceeded with my conversion to an open cooling system. All went well, new 195-deg thermostat, new coolant, flushed entire system. This is the 2nd time I THOROUGHLY flushed the heater core as well as the entire engine/radiator. I had previously removed the HCV, so no issues there. So, I'm having the same symptoms as before: VENT puts out a tiny bit of heat. HEAT puts out nearly nothing but cold air. DEFROST puts out same as VENT...not much to write home about. 1. I checked the blend door cable and it works beautifully, extending all the way to warmest setting--and it pushes the flap to it's limits, which is the black plastic stop you can see on HornBrod's picture above. 2. After my frigid trek this morning, I checked both heater hoses and they were hot to the touch, as was the top radiator hose. 3. Air volume coming out is adequate--just not hot. 4. As I toggle through the VENT, HEAT, and DEFROST sections of the controller, actuators seem to be quickly doing their job. Air toggles like it's suppose to. 5. Pushed open and peeked through the blend door and I see the squirrel cage and all looks clear. Before I diagnose this as a bad heater core, is there any way there might be another actuator inside the air box that may be faulty/disconnected or something that would cause these symptoms? Anything I can look for under there that might be obvious? I've looked at some heater box pics, but I'm really not familiar with the inner workings of this beast. i really hate the thought of pulling my dash, evacuating my original refrigerant and replacing both heater and AC cores if there might be one more thing that I can check or try. Link to comment Share on other sites More sharing options...
HOrnbrod Posted January 2, 2018 Share Posted January 2, 2018 Haven't read through it all, but have you flushed out the system including the heater core with a good radiator flush product? Link to comment Share on other sites More sharing options...
coolwind57 Posted January 2, 2018 Author Share Posted January 2, 2018 52 minutes ago, HOrnbrod said: Haven't read through it all, but have you flushed out the system including the heater core with a good radiator flush product? No, at the time I chose not to use any of these products. I had heard others say it was the beginning of the end of their components afterwards (water pump, heater core, etc). I figured that I'd better not expose my 28 year old system to anything that might weaken it. Perhaps I should reconsider. I may try a flush product and circulate just the heater core loop. I'm thinking the heater core is not providing enough surface area to provide the heat exchange, possibly due to some sludge that flushing alone is not fixing. Also, I'm wondering if my water pump may be weak.... I am getting heated hoses throughout, so some is obviously circulating. Perhaps its just strong and adequate enough to prevent overall system overheating but a bit too weak to shove much coolant to the heater core..... Just thinking out loud. Link to comment Share on other sites More sharing options...
HOrnbrod Posted January 2, 2018 Share Posted January 2, 2018 Been flushing my system out at least bi-annually for many years now. It has the original heater core and always has good heat. It may be too late, but I think you should definitely try a flush before digging into replacing the core. I always use Prestone products with only distilled water, but they are all probably good. Link to comment Share on other sites More sharing options...
Ωhm Posted January 2, 2018 Share Posted January 2, 2018 More just thinking out loud. Seems everything is working as designed, except for heat. How about fresh air in being clogged. Link to comment Share on other sites More sharing options...
yxmj Posted January 2, 2018 Share Posted January 2, 2018 Cheap any easy flush is every day household vinegar........ I remove both hoses off the core......i then pop on 2 scrap hoses......elevate the open ends. With a funnel fill the lower hose until vinegar comes out the other.....let sit for about 20 min.....dump out into a pail.....now flush the core buy using low pressure water (garden hose) pump water both ways through the core....repeat process a couple of times.....your output water should be as clear and have one same flow rate as the input...... Link to comment Share on other sites More sharing options...
coolwind57 Posted January 2, 2018 Author Share Posted January 2, 2018 59 minutes ago, Ωhm said: More just thinking out loud. Seems everything is working as designed, except for heat. How about fresh air in being clogged. Blower motor/squirrel cage is clear. I have good blower strength. Cowl area had been cleared a while back. no junk in there when I took out my wiper assembly a couple of weeks ago. 1 hour ago, HOrnbrod said: I think you should definitely try a flush before digging into replacing the core Yes, I'll try a chemical flush....or a vinegar flush or both. Anything other than pulling that dash and core. Link to comment Share on other sites More sharing options...
Keyav8r Posted January 3, 2018 Share Posted January 3, 2018 Pulling the dash and core is a PITA but not the end of the world. I’ve had the dash out in my old ‘88 and my ‘91 and managed to get it all back together. Just take photos of each step, bag and tag your fasteners as you take them out, and be careful not to pinch vacuum hoses or wires when you go back together. That being said, I’d try everything else first to cure the heat problem. The upside is that heater cores are readily available and not too expensive. Link to comment Share on other sites More sharing options...
coolwind57 Posted January 3, 2018 Author Share Posted January 3, 2018 I had rebuilt a heater box in a 99 Cherokee about 6-7 years ago. Agreed, PITA but doable. Link to comment Share on other sites More sharing options...
zomeizter Posted January 3, 2018 Share Posted January 3, 2018 Coolwind, I went through exactly what you describe, although this was on a Dodge pickup, replacement of the heater core solved the issue, good luck man... Link to comment Share on other sites More sharing options...
coolwind57 Posted January 3, 2018 Author Share Posted January 3, 2018 Just saw a video of a guy that blew out heater core with compressed air then used CLR and allowed it to soak for 20 minutes or so. Flushed the heck out of it with water afterwards. May be my last ditch effort. Link to comment Share on other sites More sharing options...
coolwind57 Posted January 3, 2018 Author Share Posted January 3, 2018 Link to comment Share on other sites More sharing options...
Keyav8r Posted January 5, 2018 Share Posted January 5, 2018 I suggest regulating the air pressure down. If you have some blockage you could blow the core open. Maybe start with 5-10 PSI and work your way up. Also, put a hose on the side you’re not pressurizing and point the end down under the truck in case you blow some crud out of the core. Might save a lot of effort cleaning up the engine bay, not to mention being safer. Link to comment Share on other sites More sharing options...
yxmj Posted January 5, 2018 Share Posted January 5, 2018 As above.....your heater core was not made to withstand high psi air flow....you will do more damage than good using air on an old core.....it was meant to flow fluid....you want it to flow fluid..to give you heat..use a low pressure hose to wash it out and you might save it......or just get a new core and call it a day? If it helps....check my avatar....I am from Winnipeg..... First thing we learn is how to get the heater going.....-29 today......I drove home in a toasty warm 1992 2.5 YJ......i use the vinegar wash described above.....on all my jeeps Link to comment Share on other sites More sharing options...
coolwind57 Posted January 5, 2018 Author Share Posted January 5, 2018 10 hours ago, Keyav8r said: Also, put a hose on the side you’re not pressurizing and point the end down under the truck in case you blow some crud out of the core. Might save a lot of effort cleaning up the engine bay, not to mention being safer. Yes, was planning on adding an old coolant jug. Keeps engine bay cleaner, plus I want to see what the heck might had been in there. 8 hours ago, yxmj said: your heater core was not made to withstand high psi air flow....you will do more damage than good using air on an old core Absolutely. My plan is to use the compressed air only at low pressure...basically as a different, non-liquid medium to help better clear out old coolant so that my vinegar and/or CLR can do it's thing. 8 hours ago, yxmj said: or just get a new core and call it a day? More like call it a weekend with my schedule. I never seem to have more than 2 hours to work on any one thing. Probably do it in a day if all the star line up just right. Thank you. I sure appreciate your comments, fellas. Link to comment Share on other sites More sharing options...
Eagle Posted January 5, 2018 Share Posted January 5, 2018 Out of curiosity, do you still have the heater control valve in the coolant hoses under the hood? If so, have you verified that it's working? The HOs did away with that valve, and it might be something for you to think about. Link to comment Share on other sites More sharing options...
HOrnbrod Posted January 5, 2018 Share Posted January 5, 2018 8 hours ago, coolwind57 said: My plan is to use the compressed air only at low pressure...basically as a different, non-liquid medium to help better clear out old coolant so that my vinegar and/or CLR can do it's thing. I wouldn't use air pressure except as a last resort. Your cooling system has probably never been properly flushed since new. The first thing to clog up is usually the heater core, because it gets no flow unless the heater valve is open and sits idle at least 1/2 the year corroding up. Do a chemical flush via the directions through the whole system first, see what happens, then do your specific heater core stuff if needed. Just my recommendation..... Link to comment Share on other sites More sharing options...
coolwind57 Posted January 8, 2018 Author Share Posted January 8, 2018 On 1/5/2018 at 1:49 PM, Eagle said: Out of curiosity, do you still have the heater control valve in the coolant hoses under the hood? If so, have you verified that it's working? The HOs did away with that valve, and it might be something for you to think about. On 12/28/2017 at 1:17 PM, coolwind57 said: A couple of Months ago, I had only removed my heater valve junk and reverse-flowed my heater core and have done nothing since. No valve any longer. Link to comment Share on other sites More sharing options...
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