GQ Glow Control Unit Issue

[MC97GQ]

Morning all,

I was wondering if you guys could help,

When warming my glow plugs the circuit seems to be cutting in and out out during the glow sequence, dash lights go dim when plugs are warming, then bright , then dim and so on.

Battery is fully charged, new glow plug relay and glow plugs. So the next thing is a new glow control unit, Problem is I spoke to Garry at Nizzbits - $870 for a new one. Now a mate of mine has a 95 model GQ so we thought we would try to swap them out and see if it is the unit or something else, but the problem is in late 95 Nissan changed the wiring and glow control units. and all the info in the manuals with regard to wiring diagrams I can find are for early 95 model or earlier.

I would like to put a momentary push button to control the glow circuit as a temporary measure but I would like to tap into the original wiring. So my question is does anyone know the wiring arrangements for a 97 GQ TD42.

I hope this makes sense

Any help appreciated

Mark

[97_gq_lwb]

I wonder if the 97 td42 is the same as the 97 2.8 glow control unit
it's pn is 407901-3210
But if you check your glow relay beside the battery under the cover it has 4 wires two larger ones and two small one should be green with a white trace and go to the glow controller.
The other smaller wire should have positive constantly.
If you switch the green wire with a white trace to earth it will activate the relay i just removed my glow controller altogether and have a switch on the dash but i lost the tacho and had to fit one to the cluster from an earlier model

[Yendor]

Hi Mark,

From what you have posted, I don't think you have a problem with your glow plug circuit or control unit.

It is normal for the glow plugs to pulse on and off, even after the engine has started (depending on engine temperature).

Are you having cold start problems?

The dash lights going dim and bright is due to voltage drop (when the glow plugs are heating).

This could be caused by a bad earth, bad electrical connection, old corroded wiring or a combination of all three.

Cheers Rodney

[97_gq_lwb]

Another problem that causes poor starting is air in the fuel system the pump on the filter should remain firm try pumping it before starting it.

[97_gq_lwb]

Ok appears they changed the glow relay wiring so check it the rd28 glow unit earth switched the glow relay basically it put an earth to the relay to turn it on through the green wire white trace .
I just fitted up an earlier td42 glow controller and it positive switches the glow relay feeds a positive power to the relay to turn it on through the green wire white trace.
Here is what i can see happening the glow light on the dash comes on for a few seconds then goes off but it still powers the glow plugs a little while afterwards.
Then it turns them on and off a about 3 times before it eventually stops.
So if yours works the same way you would positive switch the glow relay not earth like i first stated.
When you check it one of the smaller wires (on mine it is green red trace) would have a constant earth and you would feed a switched positive to the the green wire white trace as a bypass switch.
According to the diagram it looks like earlier glow relays should have a black earth and a green white trace positive switch .

[MC97GQ]

Thanks guys for all your input, I spent the last hour or so mucking around cleaned all the earth straps to the engine and body as well as the positive straps and terminals on the battery. All the same symptoms are still happening, although the truck seems to be cranking over better. The problem is with me being so slack I cannot remember if my trucks glow system has always done it or if it started some time after I purchased it.

I will have to leave the truck outdoors tonight and see if it starts better in the morning, thanks again for all your help.

Mark

[Yendor]

Check the voltage at the glow plugs and across the battery with the glow plugs on, both readings should be about the same.

Did you check the connections at the main fuses near the battery and the connectors near these fuses?

If you do have a bad connection they will feel hot after the glow plugs have been on.

[97GQ_LunchBox]

Hi guys sorry to hijack the thread but I can’t find what I need to know anywhere and your already talking about what I need to know I think…?
I have a 97 GQ td42 but had to put in the new engine out of a 93 after a snorkel malfunction during a water crossing last year and impressively blew out the old engine :-( you can see straight threw it!!

Ever since then (I think it's hard to tell really I never noticed anyway) the afterglow function doesn’t turn off at all no matter how long I've been running or the engine temp
I've checked and cleaned all the connections and I have no trouble starting even on cold mornings.

So my questions are
Is this normally or do it have an issue?
Is it something I need to fix ASAP or not that big a deal?
And will that switch you were talking about earlier work? eg only engage the glow plugs on start-up but then switch of after so they don’t keep going?

[Yendor]

Hi guys sorry to hijack the thread but I can’t find what I need to know anywhere and your already talking about what I need to know I think…?
I have a 97 GQ td42 but had to put in the new engine out of a 93 after a snorkel malfunction during a water crossing last year and impressively blew out the old engine :-( you can see straight threw it!!

Ever since then (I think it's hard to tell really I never noticed anyway) the afterglow function doesn’t turn off at all no matter how long I've been running or the engine temp
I've checked and cleaned all the connections and I have no trouble starting even on cold mornings.

So my questions are
Is this normally or do it have an issue?
Is it something I need to fix ASAP or not that big a deal?
And will that switch you were talking about earlier work? eg only engage the glow plugs on start-up but then switch of after so they don’t keep going?

What makes you think your glow plugs are not turning off?

Have you put a voltmeter of test light on the glow plug busbar to confirm they are not turning off?

If it doesn't turn off it will quickly burn the glow plugs out.

[97GQ_LunchBox]

Thanks for the reply mate, yea there not staying on constantly it’s the like the afterglow doesn’t turn of

When its running as far as I understand it any way the afterglow will click the glow plugs on and off for a few second at a time several times until the car reaches a certain temperature then stop??

Mine doesn’t stop it will keep clicking the glow plugs on and off continually regardless of engine temp

Oh and yes I’ve tested it with a multi meeter at the glow rail to make sure

[97_gq_lwb]

Is your temperature sender working ok as the afterglow won't stop until it reaches about a quarter on the gauge from memory.

[97GQ_LunchBox]

Yea it is that was one the first things I checked unless it’s a different sender to the temp gage one.

I cleaned and checked at the connections as well

I did get the controller unit wet about a year ago when I drowned the car and killed the old engine
But also as it is a different motor form and older model I though the temp sender might be different and that is stuffing it up?

do you know if they were different senders over time I have a 97 but the motor is out of a 89?

[97_gq_lwb]

I drowned mine it had a 2.8 glow controller still in it from when i changed it to a 4.2 and it was stuffed in a week from corrosion.
I just ripped it out and wired in the old 4.2 controller.
Is yours a factory 4.2 or 2.8 got any pics of the glow controller.

[Yendor]

Thanks for the reply mate, yea there not staying on constantly it’s the like the afterglow doesn’t turn of

When its running as far as I understand it any way the afterglow will click the glow plugs on and off for a few second at a time several times until the car reaches a certain temperature then stop??

Mine doesn’t stop it will keep clicking the glow plugs on and off continually regardless of engine temp

Oh and yes I’ve tested it with a multi meeter at the glow rail to make sure

Once the engine has started the glow plugs should pulse on and off for about another 15 seconds, then turn off completely.

To the best of my knowledge the coolant temp sensors are the same in both your engines.

I have attached the resistance readings for the temp sender.

Yes it is different to the one for the gauge. No I don't know it's exactly location, but the 2 wire colours at the sender should be a Black wire and a Blue with a Red trace wire.

From what you have posted I think the most likely cause of your problem will be the glow plug control unit.

I would still check the operation of the coolant temp sensor and glow plug control unit inputs before buying a new unit.

[97GQ_LunchBox]

Awesome thanks for the tips guys

Yes it was a td42 from stock
I've had a look at the control unit and can’t find any faults and I did clean with contact cleaner and then spray WD40 asap after drowning it but admittedly I'm no expert

I will be looking into finding and checking that different temp sender and thanks heaps for the resistance measurements that will help

And if that doesn't work I'll see if a mate will letting me try his control unit see if that fixes the problem

I was thinking as someone mentioned earlier a switch between the control unit and the glow relay so that I can just turn it of manually after start up would be a cheap and easy fix to the problem as I don’t want to lose my taco and everything else the control unit dose. But I don’t know if that will cause further issue with the control unit.

Will that work or just cause more issues?

[97_gq_lwb]

That is what is confusing me i have never seen a later 4.2 glow controller are they different and like the 2.8 one or not .
The 2.8 one modified the tacho signal where as the early td42 one doesn't.

[97GQ_LunchBox]

Ok well i might be wrong and the controller doesn't effect things like the taco and i can just replace it with button to the glow relay but i don't know so don't wanna stuff with it till i do and cant find that info on a Google search

[Yendor]

The glow plug control unit for the GQ TD42 doesn't run the tacho.

If you want to bypass the controller and set up a manual switch for the glow plugs.

Just unplug the unit, find the Green wire with a White trace (pin 6) and the White wire with a Green Trace at the plug (pin 1), splice into each of these and run both wires to your manual momentary switch.

When the ignition is on and you push the switch the glow plug relay will turn on and supply power to the glow plugs.

If you also want the glow plug warning light indicator in the dash to work, you will need a relay.

Connect the relay pins to the following at the old glow plug control unit plug.

85 terminal of the relay to ground.
86 terminal of the relay to the White wire with a Blue trace (pin 5 )
87 terminal of the relay to the Yellow wire with a Green trace (pin 3)
30 terminal of the relay to ground.

[97GQ_LunchBox]

OK thanks mate that’s exactly what I needed to know you have been very helpful

If I don’t fined that the temp sender is the issue then I’ll give a go

Cheers again

[Yendor]

The glow plug control unit for the GQ TD42 doesn't run the tacho.

If you want to bypass the controller and set up a manual switch for the glow plugs.

Just unplug the unit, find the Green wire with a White trace (pin 6) and the White wire with a Green Trace at the plug (pin 1), splice into each of these and run both wires to your manual momentary switch.

When the ignition is on and you push the switch the glow plug relay will turn on and supply power to the glow plugs.

If you also want the glow plug warning light indicator in the dash to work, you will need a relay.

Connect the relay pins to the following at the old glow plug control unit plug.

85 terminal of the relay to ground.
86 terminal of the relay to the White wire with a Blue trace (pin 5 )
87 terminal of the relay to the Yellow wire with a Green trace (pin 3)
30 terminal of the relay to ground.

Edit: should be the Brown wire in pin 7, not the White wire with a green trace in pin 1

[Bender]

Hi Guys,

I am having this exact problem however cant find a definitive solution without simply replacing the glow control unit.

I have a 97 RD28T Patrol
I drowed it over the pedals last weekend
Glow plugs are not working and no light on the dash
Tacho also not working
Have tested plugs, relays, fuses except cant find a wiring diagram of the glow control unit (pretty sure its cooked)

I want to know if I can find a schematic of the control unit can I replace a cheap capacitor etc on the board or do I have to source a new Control Unit??

[Bender]

So I have been looking everywhere for a new Control Unit and the common response is "Nah mate they are rare as rocking horse shit"

Surely somebody has done an engine conversion and still has a control unit??

[FrodeS]

I too would be interrested in a wiring diagram for the RD28T (1993 SWB if it matters).