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Rear defrost install - Is the wiring there? by bmyers
Started on: 01-17-2023 07:14 PM
Replies: 7 (335 views)
Last post by: Mickey_Moose on 01-24-2023 04:22 PM
bmyers
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Report this Post01-17-2023 07:14 PM Click Here to See the Profile for bmyersSend a Private Message to bmyersEdit/Delete MessageReply w/QuoteDirect Link to This Post
In a car w/o a factory-install defroster, is the wiring for the defroster/switch/etc. still there anyway? Assuming I have the switch, relay and window, can I just plug it all in? Or is the wiring harness different?

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Spadesluck
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Report this Post01-19-2023 08:16 AM Click Here to See the Profile for SpadesluckSend a Private Message to SpadesluckEdit/Delete MessageReply w/QuoteDirect Link to This Post
I do not beleive so but I could be mistaken. I know my 87 without defrost doesn't have the wiring for it.
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Threedog
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Report this Post01-19-2023 05:47 PM Click Here to See the Profile for ThreedogSend a Private Message to ThreedogEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Spadesluck:

I do not beleive so but I could be mistaken. I know my 87 without defrost doesn't have the wiring for it.



Same. My 87 has nothing for it, recently had the whole interior out and the only wired thing towards the back was the third brake light, nothing under the dash either.
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ArthurPeale
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Report this Post01-20-2023 08:45 AM Click Here to See the Profile for ArthurPealeSend a Private Message to ArthurPealeEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by bmyers:

In a car w/o a factory-install defroster, is the wiring for the defroster/switch/etc. still there anyway? Assuming I have the switch, relay and window, can I just plug it all in? Or is the wiring harness different?



You may be asking for more trouble than it's worth. I've read that replacing the rear glass is a logistical nightmare.

I've also read that the engine heat serves to keep that specific window frost free, but I've yet to put that to the test.

Hello, fellow Northerner !

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cebix
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Report this Post01-21-2023 02:07 PM Click Here to See the Profile for cebixSend a Private Message to cebixEdit/Delete MessageReply w/QuoteDirect Link to This Post
I can cofirm, been driving in the winter and never felt the need for a heated rear window. The engine serves a good enough job to heat that glass in my opinion.
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theogre
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Report this Post01-22-2023 10:30 AM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
I have this option and very little use for it.

Engine doesn't get warm enough when you start the car and windows have frost or ice on them. That's about only time I use it because scraping ice on rear glass is a pain w/ most scrapers. Start the car, push switch then clear other glass.
Side Note: Make Sure you have a spare door key doing this because very easy to lock yourself out w/ engine running. Many people automatically hit the lock getting out of car w/o thinking even w/ manual "Fiero" style interior locks. Easier still w/ any power locks even before near everyone has fobs. (Many newer cars try to fight you locking w/ engine running and driver gets out.)

Note that the Rear Defog only works for a few minutes even when you push the switch.
when push First time stays on 10 or 5 minute. After until turn off I-key 5 or 2.5 minutes.

Because the "Relay" is a Timer Relay and GM used 2 or more timing setups over the years. Don't count on GM and other doc's always saying 10/5 or whatever because doc's don't get updated for timing. The Timer Relay use here have timing data printed on them. My 87 has 5/2.5 timing while older models may have 10/5 timing.

I believe RD wiring is only on cars came w/ the option. Isn't like Power Latch wiring for deck lid that mostly complete in many to all Fiero covered in my Cave, Trunk Release
Not digging thru my parts car w/o this covered under cover and stuff. Don't remember seeing a "spare" plug in the dash for this. You see 2 plugs under blank cover or power lid cover if has any wiring or when you pull back dash to change dash bulbs.

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RWDPLZ
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Report this Post01-22-2023 11:20 AM Click Here to See the Profile for RWDPLZClick Here to visit RWDPLZ's HomePageSend a Private Message to RWDPLZEdit/Delete MessageReply w/QuoteDirect Link to This Post
On my 84 with the center vent, the engine heat works perfectly as a rear defroster, even when it's -10F outside.

The defog didn't work when I got the car because several of the lines were damaged, I was able to repair them with the Permatex kit

https://www.permatex.com/pr...defogger-repair-kit/

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Mickey_Moose
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Report this Post01-24-2023 04:22 PM Click Here to See the Profile for Mickey_MooseClick Here to visit Mickey_Moose's HomePageSend a Private Message to Mickey_MooseEdit/Delete MessageReply w/QuoteDirect Link to This Post
Pull the plate off where it mounts on the dash - if you have a spare connector there with the trunk release, then it is wired.
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