Replacing the capacitor in the Coolant Temp Gauge
Posted: 06 Jan 2014, 16:44
This has been covered in a few other places, here;
http://www.thesamba.com/vw/forum/viewto ... c&start=42
And here;
http://www.vanagonauts.com/Warning-Light-Fix241.htm
But I thought I'd add in my couple of pics to the mix of info.
Firstly - Symptoms - I was occasionally finding that the Coolant Temp LED would flash for longer than was normal when the van was first started (i.e. it would flash for 1-2 mins). I temporarily disconnected the Coolant Level relay and the LED still flashed (with a low temp reading on the temp gauge) - so I concluded that it was not the coolant level circuit that was at fault.
Culprit - Turns out that there is a capacitor in the coolant temp gauge. The cap is used to give the 5-7 secs of flashing when you first turn the key (the LED test at start-up). However over time this cap can degrade to the point that it either behaves as mine did or just gives a permanently flashing LED.
Important - It's important to note that a broken capacitor is not usually the cause of the LED flashing - it's much more likely to be that the coolant level is actually low, or the coolant level circuit is playing up (or infact that the coolant temp is high - although this is fairly obvious as the gauge will also read high). So, check all of those first!
To replace the capacitor, you will need a 16 volt 10 uf (micro farad) tantalum capacitor.
The Fix - First, take the coolant gauge out from the gauge cluster - the method for this will vary depending on if you have a rev counter etc but it's all pretty straightforward removal of mounting screws etc.
Next you'll need to remove one of the rivets that hold on the gauge background - I ground the back off with a dremel then pulled the rivet out with needle-nose pliers.
I started trying to remove both rivets (you can see the hack job I made of the front!), but once one is out the gauge background can be swung out of the way on the remaining rivet;
The old capacitor is soldered onto these two pads with the capacitor body obviously being on the underside of the board as we are seeing it here (I didn't get a before pic so you'll have to take my word for it);
There seems to be two options to remove the cap - either remove the entire board from the metal housing (which involves desoldering the two posts that hold the board in the housing), or removing the cap with the board in place .... I went for option two.
You'll need to melt the solder on those two pads, using desoldering braid or a desoldering pump to remove the solder, then gently push down on the legs (while the soldering iron is melting any remaining solder to release the old capacitor). Be patient as you have to alternate heating between the two legs but eventually it should release and drop down into the housing below the board.
You can then carefully retrieve the capacitor from under the board using needle nose pliers or tweezers - be really careful of the temp gauge mechanism, it is extremely delicate and there are lots of tiny little components in there that can be easily bent.
Next, get your new capacitor, identify which is the positive leg, then snip both legs so that they are about 5mm long. You can then position the capacitor on the solder side of the board with each leg on one of the solder pads. Note that the outside pad is the positive one i.e. the one on the right in the pic above; so make sure that the positive leg of the new cap in on that pad. Then solder in place.
Again, be really careful that the cap isn't contacting any of the other pads (or that thin piece of wire that runs from the post at the top to the gauge - you can just see it in the pic).
And that's it - replace the gauge background - the rivet is 1/10" (2.54mm) - so I replaced that with a tiny screw and nut - you could probably get away with a screw and a dab of glue-gun plastic on the back)
Reassemble everything and you should now have a flashing LED that works correctly.
http://www.thesamba.com/vw/forum/viewto ... c&start=42
And here;
http://www.vanagonauts.com/Warning-Light-Fix241.htm
But I thought I'd add in my couple of pics to the mix of info.
Firstly - Symptoms - I was occasionally finding that the Coolant Temp LED would flash for longer than was normal when the van was first started (i.e. it would flash for 1-2 mins). I temporarily disconnected the Coolant Level relay and the LED still flashed (with a low temp reading on the temp gauge) - so I concluded that it was not the coolant level circuit that was at fault.
Culprit - Turns out that there is a capacitor in the coolant temp gauge. The cap is used to give the 5-7 secs of flashing when you first turn the key (the LED test at start-up). However over time this cap can degrade to the point that it either behaves as mine did or just gives a permanently flashing LED.
Important - It's important to note that a broken capacitor is not usually the cause of the LED flashing - it's much more likely to be that the coolant level is actually low, or the coolant level circuit is playing up (or infact that the coolant temp is high - although this is fairly obvious as the gauge will also read high). So, check all of those first!
To replace the capacitor, you will need a 16 volt 10 uf (micro farad) tantalum capacitor.
The Fix - First, take the coolant gauge out from the gauge cluster - the method for this will vary depending on if you have a rev counter etc but it's all pretty straightforward removal of mounting screws etc.
Next you'll need to remove one of the rivets that hold on the gauge background - I ground the back off with a dremel then pulled the rivet out with needle-nose pliers.
I started trying to remove both rivets (you can see the hack job I made of the front!), but once one is out the gauge background can be swung out of the way on the remaining rivet;
The old capacitor is soldered onto these two pads with the capacitor body obviously being on the underside of the board as we are seeing it here (I didn't get a before pic so you'll have to take my word for it);
There seems to be two options to remove the cap - either remove the entire board from the metal housing (which involves desoldering the two posts that hold the board in the housing), or removing the cap with the board in place .... I went for option two.
You'll need to melt the solder on those two pads, using desoldering braid or a desoldering pump to remove the solder, then gently push down on the legs (while the soldering iron is melting any remaining solder to release the old capacitor). Be patient as you have to alternate heating between the two legs but eventually it should release and drop down into the housing below the board.
You can then carefully retrieve the capacitor from under the board using needle nose pliers or tweezers - be really careful of the temp gauge mechanism, it is extremely delicate and there are lots of tiny little components in there that can be easily bent.
Next, get your new capacitor, identify which is the positive leg, then snip both legs so that they are about 5mm long. You can then position the capacitor on the solder side of the board with each leg on one of the solder pads. Note that the outside pad is the positive one i.e. the one on the right in the pic above; so make sure that the positive leg of the new cap in on that pad. Then solder in place.
Again, be really careful that the cap isn't contacting any of the other pads (or that thin piece of wire that runs from the post at the top to the gauge - you can just see it in the pic).
And that's it - replace the gauge background - the rivet is 1/10" (2.54mm) - so I replaced that with a tiny screw and nut - you could probably get away with a screw and a dab of glue-gun plastic on the back)
Reassemble everything and you should now have a flashing LED that works correctly.