1st one cracked out today...

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dc2001
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1st one cracked out today...

Post by dc2001 » September 12th, 2014, 4:54 pm

I arrived to a customers house on a hot day today and the car was parked out in the sun. We moved it into the garage and turned on the a/c. Not the defrost just the normal vents. This is where it goes bad. After a minute or two of cooling I placed the heat exchanger on the small star to cool it down. After about 5 seconds the star cracked out to about 8 inches instantly. It slowly continued to grow over the next 15 minutes or so to about 12 inches.
Should I have waited longer to place the heat exchanger on the hot glass? I called Delta to see what they say and a lady said I could turn the a/c on the defrost to cool it which I thought was a big no no. What do you all say?

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Re: 1st one cracked out today...

Post by Brent Deines » September 12th, 2014, 5:42 pm

A lot of technicians on this forum will disagree with me on this but I have used the A/C through the defrosters a lot over the years and have yet to crack a windshield doing so. While we rarely see temperatures over 100 degrees in Oregon but 100+ was quite common in Montana and I used the A/C all the time.

If the car has not been running, the A/C will blow warm air on the glass and gradually cool down. As it does the glass will also cool down. If the car has been running and the air coming out of the A/C is already cold, the air inside the car is also cool, so just keeping it running is not going to cool the glass any more unless it is directed through the defroster vents. If the inside of the glass is still really hot, just raise the temp of the A/C a bit so it is blowing warm air first and then gradually move to colder temperatures.

Do you know the temperature of the heat exchanger when you placed it on the windshield? What was the temperature of the glass. It's probably a bit early to make assumptions but if the outside of the glass was very hot and you put a cool or cold heat exchanger directly on the damage, the thermal shock certainly could cause a volatile star break to run. I always try to manage the temperature of the entire surface of the glass, or at least an area of several inches surrounding the damage before using a moisture evaporator and/or heat exchanger directly on the damage.

The fact that the crack kept growing for 15 minutes indicate the damage was very volatile indeed. You can never be sure before you start so you always have to assume that is the case and proceed cautiously. Regardless of what you do to control the temperature from inside the car, I recommend getting the windshield into a shaded area or at least covering the glass with a hood protector or blanket to drop the temperature from the outside.

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Re: 1st one cracked out today...

Post by dc2001 » September 12th, 2014, 7:02 pm

I don't know the exact temp of the glass as I have not bought a thermometer for that yet but I know it was too hot to place a bridge on it. I could touch it for a few seconds bit that's about it. It was about 99 outside and the it was in direct sunlight until we moved it Into the garage. I keep my kit in my garage so my heat exchanger was warm to the touch when I placed it on the windshield. I think next time I will use the heat exchanger all around the break first like you stated and get the rest of the glass cooled down and then work towards the break. And I'll let it cool a little longer before using the heat exchanger. Thanks for the reply.

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Re: 1st one cracked out today...

Post by Mr Bill » September 14th, 2014, 9:22 am

I would have stayed away from the heat exchanger in this case.
You want the whole windshield to cool down. Not just the chip area.
If the heat exchanger is more than 10 degrees cooler than the WS, you could have a crackout.
Glass does not like a sudden change in temp
If you have ever washed dishes and rinsed a hot glass under hot water only to have it crack on you, you will know what I mean.
Personally, I would only use the heat exchanger to cool the chip area after I had used the Drystar to remove excess moisture.
A hand held infrared thermometer might be helpful to let you know what temperatures are present across the windshield.
The black "frit" area at the bottom of the windshield can often be 20 degrees hotter than the rest of the windshield. This can cause thermal stress on the glass.
I like to place a chip saver over the chip and then lightly mist the whole windshield with water from a spray bottle. Let the water evaporate, and then repeat as necessary, and take your time.
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Re: 1st one cracked out today...

Post by Brent Deines » September 14th, 2014, 12:38 pm

Mr Bill wrote:I would have stayed away from the heat exchanger in this case.
You want the whole windshield to cool down. Not just the chip area.
I agree with Mr. Bill.

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Re: 1st one cracked out today...

Post by clearquest » September 14th, 2014, 2:58 pm

One word..........patience. Pull the car in out of the sun and wait. Tell the customer it may take 20 or 30 minutes longer because of cool down. Do some paperwork, organize your tools, visit the Delta Kits Forum on your smart phone! Pass a little time instead of forcing the issue. Same thing goes on stubborn breaks sometimes....be patient,

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Re: 1st one cracked out today...

Post by bill lambeth » September 14th, 2014, 3:40 pm

clearquest wrote:One word..........patience. Pull the car in out of the sun and wait. Tell the customer it may take 20 or 30 minutes longer because of cool down. Do some paperwork, organize your tools, visit the Delta Kits Forum on your smart phone! Pass a little time instead of forcing the issue. Same thing goes on stubborn breaks sometimes....be patient,

Ageed ! Except I visit the GW website !

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Re: 1st one cracked out today...

Post by candyman » September 15th, 2014, 9:28 pm

Your Mistake most likely was the heat ex-changer. Never place over break. I learned the hard way as you did. Circle the break instead, a few inches out. I rarely use the heat ex-changer for that reason. I use the ac vents ( not defrost) to help cool vehicle and or open windows and doors . I want that glass temp under 90 even if I have to wait. If the glass isn't cool more than six or more inches out the heat will return quickly. That's why so many prefer to cool the entire windshield. I have high heat here on the east coast. When I can't get the vehicle into the shade, I open all the windows and doors, cover the windshield with a dark green or white towel and pour water from the top of the glass slowly over the towel. I cover the break with a chip saver prior to doing this. I also use a water and alcohol mix spray. Each situation may require a different technique. Don't Rush it as the others have mention.
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Re: 1st one cracked out today...

Post by dc2001 » September 16th, 2014, 11:32 am

Thanks all for your replies. That was the first time I had used the heat exchanger in that manner and will be the last. Very good info and replies for me.

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Re: 1st one cracked out today...

Post by screenman » September 16th, 2014, 12:31 pm

I would hate to have to repair without the use of the heat exchanger, I feel it is one of the best tools in my kit.

Understanding expansion and contraction along with the mechanical make up of the windshield helps to understand how heat helps or hinders.
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