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Discussion Starter #1
The car stops intermittent during driving (not pleasent at all!) and does not start (ignite) again before after 5-20 minutes pause. Start motor always runs ok, but there is no sign whatsoever of ignition when the fault is present. NOTE: The glow lamp lights only weak when the problem is present. When full light intensity on the glow lamp returns (normally after waiting for 5-20 minutes)- then the engine starts easily and runs ok, but will stop again after may be 15-30 minutes driving. The things repeat. Anyone got an idea what to do?
 

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The car stops intermittent during driving (not pleasent at all!) and does not start (ignite) again before after 5-20 minutes pause. Start motor always runs ok, but there is no sign whatsoever of ignition when the fault is present. NOTE: The glow lamp lights only weak when the problem is present. When full light intensity on the glow lamp returns (normally after waiting for 5-20 minutes)- then the engine starts easily and runs ok, but will stop again after may be 15-30 minutes driving. The things repeat. Anyone got an idea what to do?
Check out relay 109 in fuse box, sounds like a problem with that .
 

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Discussion Starter #4
I have checked the relay 109 in the fuze box and it definitely seems to be at fault A:A:
The test was done on my work bench by applying 12 VDC between the terminal 30 (+12 VDC) and terminal 85 (GND). I could hear that the relay was clicking, but the ristance between terminals 30 and 87 always remained open! I will by a new one tomorrow and give you a report the result.
 

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Do these have a crankshaft position sensor? That sounds exactly like a fault I had on my last car, the CPS would start to fail when the engine got warm.. and work again when it had cooled a bit...
 

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Discussion Starter #6
Confirmation, fault positively detected and repaired, the relay 109 was the culprit :D

  1. The intermittent fault eventually turned permanent, which eased the fault finding
  2. As a test (after the bench test described earlier) I short circuited terminals 30 and 87 on the old relay by a thin copper wire before inserting it back into the fuez box. The engine started and ran ok!
  3. I replaced the old (and faulty) relay 109 with a new from the local VW dealer, and verified it was still ok (no surprise).
  4. I opened the old relay to see exactly what had made it fault, and found a break at a so called dry soldering. This is visible as cracks on the solderings on the small PCB inside the relay box. Incidentally, the majority of the solder points were dry with more or less cracking. The root cause may therefore be hudged to be a bad soldering process (to little heating) in the production of the relays, leading to cracks that eventually went into intermittent break. These kind of breaks are normally minute, and develope slowly over the years by temperature cycling and vibration, and intermittent failure is to be expected, possibly it is typical.
Thanks for the tip, strudie1 A:
 

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Confirmation, fault positively detected and repaired, the relay 109 was the culprit :D

  1. The intermittent fault eventually turned permanent, which eased the fault finding
  2. As a test (after the bench test described earlier) I short circuited terminals 30 and 87 on the old relay by a thin copper wire before inserting it back into the fuez box. The engine started and ran ok!
  3. I replaced the old (and faulty) relay 109 with a new from the local VW dealer, and verified it was still ok (no surprise).
  4. I opened the old relay to see exactly what had made it fault, and found a break at a so called dry soldering. This is visible as cracks on the solderings on the small PCB inside the relay box. Incidentally, the majority of the solder points were dry with more or less cracking. The root cause may therefore be hudged to be a bad soldering process (to little heating) in the production of the relays, leading to cracks that eventually went into intermittent break. These kind of breaks are normally minute, and develope slowly over the years by temperature cycling and vibration, and intermittent failure is to be expected, possibly it is typical.
Thanks for the tip, strudie1 A:
thats usefull information perarne , thanks for time.
 

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Discussion Starter #8
No worries, with such an active forum it is but a pleasure to really go to the bottom of things :)
 

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Discussion Starter #10
Just to round off with a few pictures (use this for practicing enclosure of pictures in replies as well:))


Photo 1: Relay 109


Photo 2: Experimental short circuit between Terminals 30 and 87(which made the engine etart again!)


Photo 3: Printed Circuit Board (PCB) with dry soldering points. The culprit is upper left, this is 100% open, but this is hard to see without a microscope...

An additional Q: Where/how do I get a maintenance/overhaul/repair manual online or on a CD for the T4 2,5TDI engine?
 
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