Defrosting

[JoeMerc]

I've always had problems with frost building up inside the truck. If it's raining out or if there is more than one person inside, I usually need to run the defroster at full blast. It's not uncommon for me to have to turn on the A/C compressor even in the winter just to aid in defrosting.

Anyway, I drove a truckload of people to and from the bar tonight in the freezing cold (those in the northeast know what i'm talking about). The defroster put up a good fight, but eventually succumb to the inevitable frost. It was so cold out that there was actually a layer of ice on the inside of all of my windows!

I let it idle with the all of the heaters running full blast to try to melt it off, but eventually got lazy and just took my ice scraper to it. I scraped down all of the windows (inside), then windexed them and dried them. I came outside 5 minutes later and everything was frosted up again. It's getting to the point where it is dangerous to drive the truck.

Bottom line, do these trucks have a history of frosting up? Are there any good anti-fog coatings to try (already tried the rain-x one to no avail). Is there anything that I can do/anything you guys have done to combat this?

 

[offroadkid]

JoeMerc,

the A/C automatically cycles on and off when DEF is chosen to help the defogging process.

I'm reading page 111 of my owner's manual, and it states For Best Results Defrosting:

Fan Speed- Any setting except "OFF"
Temperature- Towards (WARM)
Air Intake- FRESH (outside air)
Air Flow- WINDSHIELD
Air Conditioning- ON

I think one of the keys is to use FRESH instead of RECIRC. If you're using RECIRC, you're just recirculating everyones breath moisture back into your rig. FRESH brings in the dry outside air.

 

[JoeMerc]

never thought of that. makes sense. I'll be driving tomorrow in the blizzard so i'll let you know how it turns out.

 

[Poriomania]

Recirc vs fresh makes a huge difference. I run recirc as much as possible to cut down on exhaust fumes, but with two large wet dogs and two people, it just won't cut the fog until I bring in the fresh air.

 

[Dirk Diggler]

JoeMerc,

I agree with poriomania. Fresh vs. recirc. is the best thing you can do. Keep the fresh air on for best defrosting.

 

[ogsuv]

yep, recirc is the trick.
Plus make sure there is no extra moisture creeping in. I had water seeping into one of the door hinge bolts, and a little throught the torn rubber seal around the steering column where it goes through the firewall

 

[Cruisin'Carolina]

I agree....it sounds like you have a hidden source of moisture in your truck.

I had a heater core leak in a car one time that fogged up and froze the inside of the windows.....and it was a very small leak.....

I would check for intruding moisture around all door/firewall/heater/window/sunroof openings.

You have way too much moisture inside just to be from breath.

 

[cary]

Unlike every other vehicle, the A/C does not come on in the LC with the defrost. You have to turn it on manually. THe reason you use the A/C is it dehumidifies the air, even though it is blowing hot.

Cary

 

[hobbes]

The A/C comes on in my '97 automatically when you hit the defrost button (but not the defrost + feet button).

 

[JoeMerc]

Mine's a '93, and the A/C does not come on automatically. I had an adventure today driving into philly for the villanova/kansas game in the blizzard. The recirc helped, but a truck full of drunk college students didn't.

I definitely think you guys are right about the hidden source of moisture, now it's just time to track it down. My front passenger window moulding does not look like it fits right (looks almost 'rippled', like someone tried to squeeze it in who didn't have a clue what they were doing). There isn't any wind noise so I never thought it was a problem. Could this be it?

 

[offroadkid]

Unlike every other vehicle, the A/C does not come on in the LC with the defrost. You have to turn it on manually. Cary

Cary, check your owners' manual, the A/C automatically comes on in my 97 when DEFROST is on. I'm not sure what year it started though. Not all vehivcles have the switch illuminate when DEFORST is selected.

I definitely think you guys are right about the hidden source of moisture, now it's just time to track it down. My front passenger window moulding does not look like it fits right (looks almost 'rippled', like someone tried to squeeze it in who didn't have a clue what they were doing). There isn't any wind noise so I never thought it was a problem. Could this be it?

Another thing that comes to mind, being a mechanic, and I see alot of cust. complaints where people have water intrusion on their pass floor. When it's not coolant from a heater core, I find that either their A/C drain tube is plugged, so the condensation that is supposed to be draining fromthe A/C fills up in the heater box, and spills into the car. Once the debris is removed, (and I jump out from under the car), a sh!tload of water comes pouring out.

 

[PHAEDRUS]

joe,
just for giggles pull up the carpet on either side of the truck in the front seats and see if you have any water on the floors or any moisture in the carpet..... if os check out the faq on sun roofs.
Dave