Buick Park Avenue 1993 rear window defogger

[Michael J. Senay]

I am having problems with my rear window defogger. When I turn on my rear window defogger it will run about two minute then the circuit breaker kick out. Power locks, seats are on this circuit.

[airxsports]

Im having this same exact problem in my 93 ultra. I hit the defrost and it works for less then a couple minutes and stops working. The light for the rear defrost is still lit but is not defrosting the rear window. I notice my power seats and locks stop working for some time then all the sudden they work again and I can hit the defrost button and the cycle happens again.


If anyone can shed some light on this that would be great.


Michael J. Senay did you install aftermarket radio? The person I bought the car from did, when I bought it they put the stock radio back in.

Any one that can help would be great.

Thanks
Rob

[rksk]

I am not that familiar with the 93 PA, but the symptoms occur because one of the 30 amp circuit breakers is opening. The rear window defroster draws a lot of current and probably caused the circuit breaker to open, or you may have a partial electrical short. The circuit breaker for the defroster circuit also powers the seat, mirrors, and door lock circuits. When the circuit breaker opens you will loose power to all of those circuits. The circuit breaker will reset itself after it cools down, but will open again if the excessive current load or short still exists. I am not sure where the circuit breakers are on the 93 PA, but I suspect they are at the primary fuse panel. The breaker will get very warm/hot whenever the current draw is high and circuits are heavily loaded. Opening of the circuit breaker may indicate a bad breaker, or a partial short, or it may be considered somewhat normal operation because of the heavy electrical load caused by the defroster circuit.

Regards,
rksk

[dreager]

Originally Posted by rksk

I am not that familiar with the 93 PA, but the symptoms occur because one of the 30 amp circuit breakers is opening. The rear window defroster draws a lot of current and probably caused the circuit breaker to open, or you may have a partial electrical short. The circuit breaker for the defroster circuit also powers the seat, mirrors, and door lock circuits. When the circuit breaker opens you will loose power to all of those circuits. The circuit breaker will reset itself after it cools down, but will open again if the excessive current load or short still exists. I am not sure where the circuit breakers are on the 93 PA, but I suspect they are at the primary fuse panel. The breaker will get very warm/hot whenever the current draw is high and circuits are heavily loaded. Opening of the circuit breaker may indicate a bad breaker, or a partial short, or it may be considered somewhat normal operation because of the heavy electrical load caused by the defroster circuit.

Regards,
rksk

Ditto to others with problem and thanks to rksk for hitting on part of it.

I checked the fuse panel on my '92 ,which is HUGE and runs 3/4 way across located just behind engine on the firewall, and it turns out they are NOT breakers, they are 50amp fuses in relation the the door locks (which it states;dr lks).Maybe the defogger has its own breaker ? So bang goes the theory the breaker is kicking out. Somewhere else along the line there must be a relay of some sort that's overheating, unless there's a breaker somewhere in the circuit or fuse panel. Electrics are not my fav. subject.

Anyone else got ideas ?

[dreager]

There may be a solution, not sure 'cause i didn't try it. It seems to be a GM related issue. Scroll down to "SteveR" and read his summation...a melted wire at/near black box near defogger.....

http://www.automotivehelper.com/topic176997.htm

[HotZ28]

Maybe the defogger has its own breaker ? So bang goes the theory the breaker is kicking out. Somewhere else along the line there must be a relay of some sort that's overheating, unless there's a breaker somewhere in the circuit or fuse panel.

In addition to checking for poor grounds or power connections, you might try swaping the defogger relay with one used for another purpose. After a period of time, the relay (breaker) for the defogger circuit will get corroded and may not provide the amperage required to maintain the rear defogger through the full 10-min cycle. Start by replacing the relay labeled "G". The relay is located in the fuse panel under the passenger side dash. You need to remove the “hush” panel and drop the front of the glove box down to gain full access. The relay & fuse location is listed on a label which should be attached to the passenger side sound insulator. If not, the pic below is from a LeSabre of the same vintage.

[dreager]

Thank you Hotz!

I have a factory service manual but could find nothing about the location of the relay box ?? Hopefully our freeze will end here soon so I can get at it.

[dreager]

[quote=HotZ28]In addition to checking for poor grounds or power connections, you might try swaping the defogger relay with one used for another purpose. After a period of time, the relay (breaker) for the defogger circuit will get corroded and may not provide the amperage required to maintain the rear defogger through the full 10-min cycle. Start by replacing the relay labeled "G". The relay is located in the fuse panel under the passenger side dash. You need to remove the “hush” panel and drop the front of the glove box down to gain full access. The relay & fuse location is listed on a label which should be attached to the passenger side sound insulator. If not, the pic below is from a LeSabre of the same

Well no go on swapping out the relays. I took the glove box out and followed your suggested procedure, and it still cuts out.

Any ideas where the "Black box" mentioned in the link is located?

[rksk]

Originally Posted by rksk

I am not that familiar with the 93 PA, but the symptoms occur because one of the 30 amp circuit breakers is opening. The rear window defroster draws a lot of current and probably caused the circuit breaker to open, or you may have a partial electrical short. The circuit breaker for the defroster circuit also powers the seat, mirrors, and door lock circuits. When the circuit breaker opens you will loose power to all of those circuits. The circuit breaker will reset itself after it cools down, but will open again if the excessive current load or short still exists. I am not sure where the circuit breakers are on the 93 PA, but I suspect they are at the primary fuse panel. The breaker will get very warm/hot whenever the current draw is high and circuits are heavily loaded. Opening of the circuit breaker may indicate a bad breaker, or a partial short, or it may be considered somewhat normal operation because of the heavy electrical load caused by the defroster circuit.

Regards,
rksk

Rob,

Sorry for misleading you regarding the 30 amp circuit breakers. Instead of telling you that I was not familiar with the 93 PA, I should have stated that this is how it works on an 89 PA. I didn't realize the system designs had changed that much.

My Apologies,
rksk

[dreager]

Originally Posted by rksk

Rob,

Sorry for misleading you regarding the 30 amp circuit breakers. Instead of telling you that I was not familiar with the 93 PA, I should have stated that this is how it works on an 89 PA. I didn't realize the system designs had changed that much.

My Apologies,
rksk

No way you misled ! You at least got us on the trail more than I can say for anyone else, all we got there was dead air until Hotz came on the scene.At least now I've eliminated the relay as the cause. If I said anything that sounded like flaming I apologise.

The question remains, "where is the defogger black box located"?

[HotZ28]

Originally Posted by dreager

The question remains, "where is the defogger black box located"?

The “black box” is under the rear side panel, passenger side. This panel is the vertical section going from the rear deck to mate with the headliner. (Between rear door & rear window) You will need to use a trim removal tool to pop the two plastic serrated rivets out. The rear door weather-stripping will also need to be pulled forward to allow the panel to slide forward and out.

Before you do this, let’s try one more thing. I almost forgot about the early 90’s having the two circuit breakers in the main fuse panel under the drivers side dash. Notice in the pic below, these breakers are located in position 3 & 4. IIRC, one of the two, controls the p/windows, door locks, heated mirrors, and rear defogger. Best way to find the right one is to put your fingers on both, and turn on the defogger. The one that gets hot, is the one you want to remember. Anyway, swap these two breakers and try it once again. Let us know what you find.

[dreager]

[quote=HotZ28]The “black box” is under the rear side panel, passenger side. This panel is the vertical section going from the rear deck to mate with the headliner. (Between rear door & rear window) You will need to use a trim removal tool to pop the two plastic serrated rivets out. The rear door weather-stripping will also need to be pulled forward to allow the panel to slide forward and out.

Before you do this, let’s try one more thing. I almost forgot about the early 90’s having the two circuit breakers in the main fuse panel under the drivers side dash. Notice in the pic below, these breakers are located in position 3 & 4. IIRC, one of the two, controls the p/windows, door locks, heated mirrors, and rear defogger. Best way to find the right one is to put your fingers on both, and turn on the defogger. The one that gets hot, is the one you want to remember. Anyway, swap these two breakers and try it once again. Let us know what you find.


Thanks for sticking with us on this. It will be a boon to all affected if we nail this down.It's really cold here now so I will have to wait a couple of days to get at it, but I WILL follow up. It saves a lot of ripping too if I do have to go after the black box.

Thanks again for your support !

[dreager]

[quote=dreager]

Originally Posted by HotZ28

The “black box” is under the rear side panel, passenger side. This panel is the vertical section going from the rear deck to mate with the headliner. (Between rear door & rear window) You will need to use a trim removal tool to pop the two plastic serrated rivets out. The rear door weather-stripping will also need to be pulled forward to allow the panel to slide forward and out.

Before you do this, let’s try one more thing. I almost forgot about the early 90’s having the two circuit breakers in the main fuse panel under the drivers side dash. Notice in the pic below, these breakers are located in position 3 & 4. IIRC, one of the two, controls the p/windows, door locks, heated mirrors, and rear defogger. Best way to find the right one is to put your fingers on both, and turn on the defogger. The one that gets hot, is the one you want to remember. Anyway, swap these two breakers and try it once again. Let us know what you find.


Thanks for sticking with us on this. It will be a boon to all affected if we nail this down.It's really cold here now so I will have to wait a couple of days to get at it, but I WILL follow up. It saves a lot of ripping too if I do have to go after the black box.

Thanks again for your support !

****OK tonite I got at the 2 relays in driver side, and boy was it HOT! First I jiggled them and drove around for an hour (turning on each time it normally cuts off after 10 mins.) and it never cut out once?! Then I swapped them and it went back to cutting out and overheating. So on the one hand I had success, but then was back to nowhere. Last option before hitting rear "black box" is to buy 2 new relays first.

Will keep you posted.

[dreager]

[quote=dreager]

Originally Posted by dreager

****OK tonite I got at the 2 relays in driver side, and boy was it HOT! First I jiggled them and drove around for an hour (turning on each time it normally cuts off after 10 mins.) and it never cut out once?! Then I swapped them and it went back to cutting out and overheating. So on the one hand I had success, but then was back to nowhere. Last option before hitting rear "black box" is to buy 2 new relays first.

Will keep you posted.

Well bought 2 new relays and its still overheating. I think its the rear black box wiring for the defogger. Have to wait now for warmer weather.

[HotZ28]

Let's check one more thing before you move on to the "black Box". When you installed the new circuit breaker, did you look closely at the condition of the pins in the fuse/relay panel, female connector? Remember, these terminals & wires carry up to 30 amp when the defroster is on and they are subject to heat damage. The female pins/clips must provide a clean & tight connection on the male circuit breaker prongs to carry the load.