Rear defroster......arg

[Coloty]

I needed to replace both of the rear window gas shocks so I did. The bad news is that now my rear defroster doesn't work. I know the obvious thing would be that the shocks are somehow bad since the current runs through them from the way it appears. However, that not the issue and it seems like the new window shocks caused something else to go out. I used the trusty multi-meter and found I have ~14 volts of power at the drivers side upper clip, but none on the passenger side? Any ideas? the light works on the switch and it turns off after ~ 10 minutes like it should. Could it still be that switch or maybe the relay? All the other connections to the window are good.

TIA

 

[dgoodhue]

Passenger side is ground. I would check the voltage after the shock on the driver side. Check the resistance to ground on the passenger side (before and after the shock) You get a better idea where the problem is.

 

[gmcturbo]

if you have voltage at one side and not the other then the coil in the glass has cracked. follow the coil with your dvm and find the break. ive heard of people putting copper rtv over te break but i wouldnt.

 

[TYRODD]

How are all the connections/solder?

When my rear de-froster went out, the contacts were corroded and the solders had "broke" off.

 

[Coloty]

All the connections are solder and appear to be solid

This was working prior to replacing the shocks...could the new ones be bad?

The passenger side is the ground? I will check the voltage after the shock on the the driver side and resistence to ground on the passenger side tomorrow.

What is the coil your are talking about in the glass? Where is it located?

Thanks for the help/ideas and keep them comming

 

[Coloty]

After more research it seems like the passenger side should not have power, only the driver's side as someone suggested. So I checked it a little further and found no power at the bottom clip where it actually attaches to the window. The only thing that could be is the new window shock? Could that be right? The current travels thru the shock itself so maybe it is bad if it is going in at the top and not showing up at the bottom ~ 16 inhes away

 

[dgoodhue]

After more research it seems like the passenger side should not have power, only the driver's side as someone suggested. So I checked it a little further and found no power at the bottom clip where it actually attaches to the window. The only thing that could be is the new window shock? Could that be right? The current travels thru the shock itself so maybe it is bad if it is going in at the top and not showing up at the bottom ~ 16 inhes away

Check the resistance of the shock it should be low (I would guess under 20ohms) if its conducting electricity.

 

[Coloty]

Resistance was very low, practically unmeasurable so I guess that tests good. I made a jumper wire to go from the top clip to the bottom clip and the defroster works fine so it has to be the shock. It is a "Strong Arm" shock from Napa. GM lists the driver side and passenger side as a different part? I wonder if the driver side is specialized to conduct electricity better or something odd-ball like that?

 

[Coloty]

OK....so now I'm stumped. The jumper wire gives power to the entire grid so I assumed it would work on my last post....WRONG. Tested it this morning driving into work and it still doesn't work. Not talking hard core ice or snow here....just lightly fogged and it didn't even touch it? So what gives? The entire grid has ~14 volts with the jumper wire on the driver's side and still no worky? Does that definitely point to a bad ground on the passenger side? All connections are nice and solid. What should be tested now?

 

[dgoodhue]

If you have 14 volts at the grid, then your next step is too check to the passenger side ground. You would want to check the resistance to ground (instead of voltage) I think their is a ground strap on the Ty tail gate, so make your measure from that reference.

 

[Coloty]

Well the ground tested bad as well
So I jumpered the ground wire and guess what
We have spark!!
Left the wire there to test again Today and it works like a champ

So the moral of the story is that the Strong Arm gas shocks are junk when it comes to electrical conductivity. They are great to raise/lower the glass....but little else. Thank you very much everyone for your help. Now I can see those Mustangs in the rear view once again