BucketTrucker688 Posted February 16 Share Posted February 16 My 91 rd688s windshield fogs up severely in snow plowing conditions. I feel that the heater core and ac evaporator should probably be cleaned, is this something possible to do without removing either of them from the dash? I feel like I'm not getting enough airflow to the windshield to keep it thawed. Any tips? Thank you Quote Link to comment https://www.bigmacktrucks.com/topic/73872-rd-heater-core-cleaning-methods-windshield-fogging-issue-in-snow/ Share on other sites More sharing options...
Joey Mack Posted February 16 Share Posted February 16 I am well versed in this... remove the screws where the large duct goes up to the heater core housing. there is a rubber boot that seals the duct. slide it back a bit.. it may be dry rotted. it is a PITA to get back in place when your done.. I made a cardboard tube round enough to fit over my shop vac. hose.. (12-16 inches long) then I flattened all of it but the round end for the vac. I put layers of duct tape over the flattened end to keep it flat. then I cut a rectangular hole on one side ( not through both sides, just one) , in the flat end 3/4'' from the end.. basically making a sideways sucker for the vac. then I used a wedge to hold the large duct open and stuck that sucker in there. I chose cardboard because it wont damage the core. a combo of a blow gun and my fancy pants tools and some patience will get the dirt out. Quote Link to comment https://www.bigmacktrucks.com/topic/73872-rd-heater-core-cleaning-methods-windshield-fogging-issue-in-snow/#findComment-546748 Share on other sites More sharing options...
Joey Mack Posted February 16 Share Posted February 16 here is a sample of the jig i made.. all i had was a T.P roller.. Quote Link to comment https://www.bigmacktrucks.com/topic/73872-rd-heater-core-cleaning-methods-windshield-fogging-issue-in-snow/#findComment-546749 Share on other sites More sharing options...
BOBWhite Posted February 17 Share Posted February 17 Back flushing the heater core with a garden hose has always helped me get my heater back. Putting too much pressure on the heater core can cause it to pop and make a big job. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73872-rd-heater-core-cleaning-methods-windshield-fogging-issue-in-snow/#findComment-546751 Share on other sites More sharing options...
Joey Mack Posted February 17 Share Posted February 17 OH heck,,, i thought he was talking about the air passing through it to defrost his windshield.. Ooopps...... 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73872-rd-heater-core-cleaning-methods-windshield-fogging-issue-in-snow/#findComment-546752 Share on other sites More sharing options...
BOBWhite Posted February 17 Share Posted February 17 (edited) 13 minutes ago, Joey Mack said: OH heck,,, i thought he was talking about the air passing through it to defrost his windshield.. Ooopps...... OOPS! I was the one who misread! He said he wasn't getting airflow through and didn't say anything about heat Edited February 17 by BOBWhite 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73872-rd-heater-core-cleaning-methods-windshield-fogging-issue-in-snow/#findComment-546753 Share on other sites More sharing options...
Joey Mack Posted February 17 Share Posted February 17 luv it..... all good... Quote Link to comment https://www.bigmacktrucks.com/topic/73872-rd-heater-core-cleaning-methods-windshield-fogging-issue-in-snow/#findComment-546754 Share on other sites More sharing options...
mowerman Posted February 18 Share Posted February 18 On 2/16/2024 at 4:57 PM, Joey Mack said: OH heck,,, i thought he was talking about the air passing through it to defrost his windshield.. Ooopps...... me too Quote Link to comment https://www.bigmacktrucks.com/topic/73872-rd-heater-core-cleaning-methods-windshield-fogging-issue-in-snow/#findComment-546792 Share on other sites More sharing options...
Joey Mack Posted February 18 Share Posted February 18 well he hasnt come back, so maybe he fixed it.. Quote Link to comment https://www.bigmacktrucks.com/topic/73872-rd-heater-core-cleaning-methods-windshield-fogging-issue-in-snow/#findComment-546793 Share on other sites More sharing options...
mowerman Posted February 18 Share Posted February 18 our trucks used to have a shut off valve for heater core.T800 kenworth ..bob Quote Link to comment https://www.bigmacktrucks.com/topic/73872-rd-heater-core-cleaning-methods-windshield-fogging-issue-in-snow/#findComment-546794 Share on other sites More sharing options...
mowerman Posted February 18 Share Posted February 18 or maybe the door is not opening,,,good luck bob 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73872-rd-heater-core-cleaning-methods-windshield-fogging-issue-in-snow/#findComment-546795 Share on other sites More sharing options...
BucketTrucker688 Posted February 19 Author Share Posted February 19 yeah it seems like an air flow issue. i have owned the truck and worked it nearly daily since 09 and have never had this portion of the truck apart yet. is it adviseable to try and spray coil cleaner on the coils and rince it with a pump sprayer? thats what i ended up doing with my western star but that set up i could get to both sides of the heater core. Quote Link to comment https://www.bigmacktrucks.com/topic/73872-rd-heater-core-cleaning-methods-windshield-fogging-issue-in-snow/#findComment-546846 Share on other sites More sharing options...
Joey Mack Posted February 19 Share Posted February 19 What I found, was to be as dry as possible when cleaning. There is no filter for incoming air. If you work in dusty conditions, any extra moisture will cause it to clog sooner. I don't have a cure-all for this issue. I've just done my common procedure. I had it down to less than 30 minutes... There were many RD's in my life Quote Link to comment https://www.bigmacktrucks.com/topic/73872-rd-heater-core-cleaning-methods-windshield-fogging-issue-in-snow/#findComment-546848 Share on other sites More sharing options...
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