[Vwdiesel] slow glow plug relay, no glow light when engine is warm

[Roger Brown]

One thing you might want to do is to hook up an indicator light on the glow plug bus or 
fusible link if at all possible.  You should see the glow plugs getting power even at a 
warm start, although the GP dash light may not be on.  I used a pair of lighted windshield 
washer nozzles and ran the light wires down to the glow plug relay.  Actually, I need to 
modify that to put one nozzle light on each side of the fuse so I can see if the fuse ever 
burns out.  But with the actual glow plug power indicator, you can use that as your clue 
when the crank the engine over, let that light stay on for a while before turning the key.

And if you are not getting power to the GPs at a warm start, you may have a flaky relay.  
See the testing info below.  I find the real Bosch brand relays do the best job, the off 
brand relays may work some of the time, but at the fringes, they may not.  One example is 
with temp sender input.  If that is out of the range the relay is expecting, it can do 
strange things.  I've had relays that fail to turn on when high temp input is present or 
turn on and off erratically.  The Bosch relays seem to "do the right thing" in all cases.  
They'll have a maximum time and a minimum time that they will run regardless of the engine 
temp.


On 9/5/2014 12:22 PM, Roger Brown wrote:
> Some ideas below:
>     http://www.4crawler.com/Diesel/CheapTricks/GlowPlugs.shtml
>     http://www.4crawler.com/Diesel/GlowPlug.shtml
>
> Could be an intermittent connection in the socket or perhaps the connection to the 
> temperature sender on the head.
>
>
> On 9/5/2014 12:21 PM, Marciano Pitargue wrote:
>> It never rains in San Jose, CA.  But last winter, it did a bit, and my fuse
>> box got wet due to a poor seal of the windshield.  (Fixed that I hope.)
>> So, I ended up changing out the (original ?) crusty metal bodied (slow)
>> glow plug relay in my 1980 caddy with a plastic bodied glow plug relay
>> replacement.  Supposedly, this glow plug relay is for the slow glow plug
>> relay circuit that were on the 1980 vw diesel vehicles.
>>
>> Now, when the engine is cold, like first thing in the morning, I get the
>> nice warm glow of the glow plug light.  However, when the engine is up to
>> temp, no glow plug light, hence hard starting if the truck sat for about 30
>> minutes.  Before the fuse box wet event, it always used to light up no
>> matter the temperature of the engine.  And it seems the glow plug light
>> accurately tracks the power to the glow plugs.
>>
>> Checked the grounds for the relays for corrosion.  They seem clean.  One
>> thing I noticed is that when the glow plug light doesn't light, if I unplug
>> and plug in the (new) relay, sometimes the glow plug light lights.  I
>> suspect that that the glow plug relay isn't correct for my slow glow plug
>> relay circuit.  Or maybe I missed some ground points (I found 2 circular
>> fobs where a bunch of brown wires connect to.)
>>
>> Any advice from the group to address this issue?
>>
>> Thanks in advance.
>>
>> Marciano, driver of "slo-mo smokey"
>> _______________________________________________
>> Vwdiesel mailing list
>> Vwdiesel at vwfans.com
>> http://www.audifans.com/mailman/listinfo/vwdiesel
>
> _______________________________________________
> Vwdiesel mailing list
> Vwdiesel at vwfans.com
> http://www.audifans.com/mailman/listinfo/vwdiesel