Glow Plug System Mods

[Subzilla]

I know this has been discussed a hundred times and I've done some searching on the subject but I wanted to ask 2 questions since my electronics knowledge is limited. I'm modifying my GP system on the '86 with the in-line 10 ohm resistor per the DP manual. The manual calls for a 2 watt - 10 ohm resistor but Radio Shack only had a 10 watt - 10 ohm resistor. Does the higher power rating simply mean the resistor can handle more power or will it affect the characteristic of the resistor?? It's one of those long boxy looking resistors and not the little round one I had pictured in my mind.

Also, I want to install a manual push-button attached to a relay. I was thinking of connecting the relay to the power input and output lugs on the controller. Will this backfeed into the GP controller causing any damage? This seemed like a simple way to do it which is why I'm questioning my logic!!

Thanks!

[gmctd]

Connect the relay coil to the battery feed post, bring the other side of the coil into the cab, connected to your switch, other side of the switch wired to a large ring lug - mount the switch neck thru the ring lug to the steel dash.

Push the switch to provide the ground return for the relay coil

[More Power]

A 10 ohm 2-watt resistor is a common one. RS should have it. The wattage rating just means what amount of heat it can dissipate without damage. A higher wattage resistor in this application wouldn't affect how it works - just harder to make it look nice in the harness. :)

Jim

[Subzilla]

RS didn't have any 2 watt/10 ohm resistors in their tray of goodies so I installed the 10 watt version this weekend. I actually modified the modification by installing an in-cab switch in line of pin C. I then put the resistor in line right at the switch to make it easy to change and to keep it out of the heat. Why the switch? So I can shut down the GP system when it's not needed like going into the store for 15 minutes. My system would always cycle again and I know my 6.2's will start a good hour or 2 after shut down without the GP's. I figure I'm lengthening the life of the whole GP system by not using it when not needed.

The 10 ohm resistor lengthened the initial time from 7 seconds to about 14 seconds. This will help this time of year but I might try the 5 ohm version as well. I can also remove this resistor totally for the hot summer use to shorten the glow time.

I didn't install the push button switch as I think 14 seconds is plenty long enough to fire old Blue right up during the Carolina winters. It does occassionally get down in the teens but mostly 20's are the normal lows.

I'm happy.

[Subzilla]

I'm embarrassed to say that I may have done something bad to my controller. I tested my switch and resistor after the installation and they performed normally. The next day, I noticed the GP light flickering and not staying on the 14 seconds that it was doing the previous day. The Blazer started so I just turned the GP switch off. Next start, the GP light came on for about a second. I tried again later and I'm not getting any GP light. Again, I have a switch in-line of pin C with the 10 ohm resistor. I'm only getting 0.33 volts to this pin without the resistor and I don't if it is suppose to get 12 volts. I dug out my TDP 6.2 engine article guide and found Jim's info on repairing and modifying these controllers. I'm not the electronics genius but just reading through the article, I'm wondering if my switch interupted the power signal that was suppose to go to the controller thereby telling the controller there's insufficient engine voltage and to continue working causing the thermistor (sp?) to overheat and fry??? This making any sense? I wonder if I shouldn't have put my switch in the ground circuit for the contoller.

I'm not happy. Please help!

[joed]

On my 82, I also wired an on/off switch in line with a resistor on pin C. I did this last spring and it seems to have no ill effects. This is in effect does the same thing GM did with the "glow plug inhibit switch", it opened after a certain engine coolant temp. was reached, preventing the glow controller from glowing.

Have you checked your +12V supply (Pin D) and ground (Pin E) lines to the controller? Loose/bad connections could cause improper operation.

Hope this helps. Joe.

[Subzilla]

Joe,
I did check pin D and had 12 volts but I didn't check the ground. I just find it strange that this all started after I was tinkering with everything but then the more I think about it, that's usually when you bump things loose or break things. That's true about the inhibit switch. Hmmm. Also, did you convert your 82 to the newer system? My 83 still has the old system with the separate relay. I'll do more probing tonight. Thanks for the help.

Mark

[joed]

Yes, I did convert to the 85+ system - should of said that. I left the old controller in place but removed the relay on the fender - that's where I installed the new style controller. I found that warmer temp glows were too long with the resistor, hence the shut off switch off switch to have the best of both worlds, longer cold glows and none on a warm/hot engine.

Joe.