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  #1  
Old 08-23-2009, 07:13 PM
cousindave76's Avatar
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New glow plug relay is not cool! Battery dies on short drives.

I have searched the forum for my problem but I can't find anyone with quite the same issue. Lot's of folks with non working glow systems or glow systems that never turn off. Not quite my problem.

Car: 1983 300SD 240k, runs smoooooth and awesome!

I replaced a bad glow plug relay box. It works great. Glow light on the dash cycles on, then off and the engine starts very nicely. Trouble is, the glow plugs do not shut off for 3 minutes, no matter what. I have read that the new relays have this 3 minute shutoff time as a new and improved built-in feature(do not want). I have recently moved within 4 city blocks of where I work. So the time it takes me to start the car, drive to work and shut it off, the glow plugs will have just turned off and the battery never gets an opportunity to recover since the alternator is giving all it's 55 little amps to the glow plugs. Doing this short trip a few times, the battery finally can't keep up anymore and I get stuck. If I drive longer distances I don't have this problem.

Also, if I let the car warm up all the way, turn off the ignition and then turn it back on immediately, the glow plugs will stay on for a full three minutes again. Heck, in this Texas heat, the glow plugs are not even needed when restarting after it's been started once that day.

I never had this trouble with my old relay because once the car was started the relay turned off and the charging system was happy.

Is there any part of the glow system that should detect the engine temp and shutoff the relay? Perhaps mine is malfunctioning? If not, is there a way I could install a manual shutoff switch on my dash that I could just turn the relay off after I start up? I want this relay to function as my old one did before it decided to depart this world.

Thanks much for any ideas!

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  #2  
Old 08-23-2009, 07:50 PM
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Temperature sensor controls the length of time the glow light stays lit, it doesn't effect the timer in the relay which is set permanently to a fixed number of seconds.

Yes, you could turn the whole glow system on/off by switching the main line to the glow relay. However, it carries a lot of current so you'll probably need to use a relay under the hood, triggered with a switch on the dash.
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  #3  
Old 08-23-2009, 07:54 PM
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That usually low cost fender mounted ford starter relay is up to this service I believe.
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  #4  
Old 08-23-2009, 07:56 PM
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There's a wire from the key switch start position to the glow relay to cut the relay when the starter motor turns. Is that wire sending the right signal to the glow relay? In my car it's a purple wire.

Sixto
87 300D
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  #5  
Old 08-23-2009, 08:00 PM
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My memory is sketchy, but I think we had a thread on this topic a few months ago. On the 123's I think the glow plugs continues glowing until the timer shuts it off.
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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13
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  #6  
Old 08-23-2009, 10:35 PM
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Quote:
Originally Posted by kerry View Post
My memory is sketchy, but I think we had a thread on this topic a few months ago. On the 123's I think the glow plugs continues glowing until the timer shuts it off.
In the original configuration, releasing the ignition switch from the start position should end the cycle. My guess is that the OP purchased one of the aftermarket Bosch "afterglow" timers, which is designed to operate the glow plugs for about three minutes following start.

The afterglow relay, however, doesn't run for three minutes if there is no start attempt. In all probablity, blocking the "start" signal would substantially shorten the cycle.
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  #7  
Old 08-23-2009, 11:02 PM
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Quote:
Originally Posted by tangofox007 View Post
In the original configuration, releasing the ignition switch from the start position should end the cycle. My guess is that the OP purchased one of the aftermarket Bosch "afterglow" timers, which is designed to operate the glow plugs for about three minutes following start.

The afterglow relay, however, doesn't run for three minutes if there is no start attempt. In all probablity, blocking the "start" signal would substantially shorten the cycle.
Yep, my memory was sketchy. The debate I was thinking about concerned the issue of whether the glow cycle ended upon engaging the starter or upon releasing the key from the start position.
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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13
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  #8  
Old 08-23-2009, 11:34 PM
cousindave76's Avatar
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Quote:
Originally Posted by tangofox007 View Post
In the original configuration, releasing the ignition switch from the start position should end the cycle. My guess is that the OP purchased one of the aftermarket Bosch "afterglow" timers, which is designed to operate the glow plugs for about three minutes following start.

The afterglow relay, however, doesn't run for three minutes if there is no start attempt. In all probability, blocking the "start" signal would substantially shorten the cycle.
Yes that is true. I did in fact buy the Bosch relay. If there was a choice of relays that operate differently, I did not know it. I purchased the only available relay I could source locally. And when it comes to parts like that I only buy new.

I never timed the relay to see how long it would glow the plugs if I don't start the engine. I know it does take three minutes after start. Would it be hard to block the start signal? Is that a simple disconnect or is there a rewire in order? And would blocking the start signal mean the plugs would be glowing while I'm cranking on the starter? How negatively would that effect my electrical system?

Thanks for the replies!
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  #9  
Old 08-24-2009, 12:13 AM
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It could be that the Relay is defective. I would take it back.

Also when I tested a single Glow Plug connected to an automotive dash type Amp Meter connected to a batter; it pegged the meter at 60 amps (as hig as the meter would go) and as it got yellow read went down to about 16 amps.
So you will not be pulling 80 amps for 3 minutes on your way to work.
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  #10  
Old 08-24-2009, 12:35 AM
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Fix it for the hell of it
 
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Quote:
Originally Posted by Diesel911 View Post
It could be that the Relay is defective. I would take it back.

Also when I tested a single Glow Plug connected to an automotive dash type Amp Meter connected to a batter; it pegged the meter at 60 amps (as high as the meter would go) and as it got yellow read went down to about 16 amps.
So you will not be pulling 80 amps for 3 minutes on your way to work.
Well, I have 5 glow plugs. If each were pulling 16 amps, thats 80 all together. Not to mention the rest of the wiring and plugs and such the electricity must flow through under normal operation. But I'm sure all together I'm not getting quite an 80 amp draw as the fuse on the relay is 80 amps and it has never popped. I do however believe it's pulling at least 55 amps because the battery very slowly drains while the engine is running and the glow plugs are glowing. After the plugs turn off I jump back up to about 13 volts and the battery once again charges up and gives me a very nice crank. No drag at all. So I know it's a good battery. I don't know FOR SURE that the alternator is putting out 55 amps. It's about 6 months old. Was tested at an alternator repair shop (not Autozone god forbid) and they told me it was working just fine.

So is the 3 minute afterglow a correctly working Bosch relay? Is there not a temp sensor or something that tells it to turn off when the engine is warm enough? If not, I think I will need to install some sort of switch to manually control the plug.

Sixto, does that purple wire from the ignition send a volt signal to the relay to shut it off? How does it work?

All this trouble because I live so close to work!
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  #11  
Old 08-24-2009, 12:55 AM
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Does the replacement relay have a 4-pin or 5-pin small connector? Afterglow relays have 5 pins.

Sixto
87 300D
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  #12  
Old 08-24-2009, 01:52 AM
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The afterglow relays are supposed to use a temperature sensor (in the water jacket) to determine how long to stay on after the engine starts. If the engine is cold, the glow plugs will stay on for up to X minutes depending on which version of the relay. If the engine is warm (~50C or so) then the relay should turn off almost immediately after the engine starts. However, a 617 engine may not have the sensor that the afterglow relay needs, since the afterglow relay was designed for later model diesels (60x series). That may be why the relay is staying on.
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  #13  
Old 08-24-2009, 02:06 AM
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The relay small connector pin outs are:

1) red/black +12V with key in run = trigger to start glow
2) violet +12V with key in start = trigger to end glow
3) blue/white +12V to dash glow indicator
4) brown ground

There will be a fifth pin for the temp senor if it's an afterglow relay.

Sixto
87 300D
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  #14  
Old 08-24-2009, 08:16 AM
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Quote:
Originally Posted by sixto View Post
The relay small connector pin outs are:

1) red/black +12V with key in run = trigger to start glow
2) violet +12V with key in start = trigger to end glow
3) blue/white +12V to dash glow indicator
4) brown ground

There will be a fifth pin for the temp senor if it's an afterglow relay.

Sixto
87 300D
I think I have the 4 pin small connector but will have to look to be sure. Thanks for the plug specs, huge help! I've not been able to find that anywhere! I'll run some tests today to see if I can figure out a way with the violet wire to control the timing myself. At the moment I'm thinking I would like to install a simple push button that allows the system to work as normal but also sends a +12v signal if depressed. I'll play with it today and see if that will work.

If it turns out I have the 5 pin small plug I'll look into replacing the sensor.

Thanks Sixto!
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  #15  
Old 08-24-2009, 08:20 AM
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I have a 3 minute relay too. What I did to get more amps in the battery was first make sure regulator on alternator is good.Second Mercedes batteries have a poor ground.I added heavy ground wire from battery to engine block.My charging after starting is 15.5 volts,then drops to 14.

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