HZJ73 1991 help me about Pre-heating timer of this landcruiser

[boroyon]

Regarding the pre heating timer circuit (unit: part number is 28521-17100) for the glow plug of Landcruiser (1991 HZJ73v),
The preheating lamp of the glow plug remained on and did not go out, so when I removed the preheating timer unit and looked at the internal circuit, I found that the two resistors circled in red in the photo were burnt out. Therefore, I would like to repair it myself, but the resistance value of this resistor cannot be read visually because the horizontal line on the surface is burnt and invisible. So, can someone tell me the values of these two resistors? I would appreciate it if you could tell me the resistance values of the two pieces in order from the side closest to the corner of circuit board.
Or, if you don't know the specific resistance value but can post an enlarged photo of this part, I would appreciate it if you could post it and reply.
If I can figure it out, I'm going to source the resistors and solder them myself.

 

[veiloctane]

looks to be an easy fix just need to find out what values they are... hopefully someone has a picture they can reference to you

 

[45Dougal]

If you remove them from the board, one of them might still be showing the right value - only one looks really fried.

This might be the result though rather than the cause. Have you checked if your plugs are fried?

Seems quite common that a plug fails short-circuit and then caused a timer to overload.

 

[veiloctane]

been trying to find a clear picture to help you i cant see the resistor value https://shopee.com.my/TOYOTA-LAND-CRUISER-HZJ-PZJ-PREHEATING-TIMER-RELAY-i.53184438.5515166050

 

[boroyon]

Thank you folks. 　Someone please send a close-up picture around this position. This unit part number is 28521-17100. 　While I'm waiting for your reply, I'll check the plug for a short circuit.
If even one of the six plugs is short-circuited, will this symptom occur?

 

[boroyon]

View attachment 3363927

been trying to find a clear picture to help you i cant see the resistor value https://shopee.com.my/TOYOTA-LAND-CRUISER-HZJ-PZJ-PREHEATING-TIMER-RELAY-i.53184438.5515166050

Thank you. I also found this site(this picture). But I also can not detect the resister value. Because this picture's resolution is little bit low. 　Thank you for your information.

 

[45Dougal]

Thank you folks. 　Someone please send a close-up picture around this position. This unit part number is 28521-17100. 　While I'm waiting for your reply, I'll check the plug for a short circuit.
If even one of the six plugs is short-circuited, will this symptom occur?

Hard to tell without the board in front of me. Something caused it to overheat. Could be long term deterioration of the component, or an external change.

Either way you don't want to fry it twice

 

[boroyon]

Or can I replace my damaged 28521-17100 to 28521-17120 (MH-6410 HZJ81V) . Because I can not get 28521-17100 that is working product. Then I am planning to get used 28521-17120 MH-6410 (for HZJ81V). Is this plan OK???
If I do this, can I guarantee that the glow will work? "Normally, the glow plug lamp will go out after a certain amount of time, so isn't there any problem with the glow operation?"　　What is difference between 28521-17100 and 28521-17120?
Are they functionally compatible?

 

[sunrk]

On my 80 series (with 1hz diesel) there is no glowplug light (if there's meant to be one - it's never lit up) - I can hear the relay shut off if don't try to crank before the timer finishes it's thing. Toyodiy says the one in my 80 being 3/92 build is 28521-17130 but I haven't really checked. I'd be more suspicious of a dry (high resistance) solder joint moreso than any sort of short circuit. If you want to repair the existing unit that electrolytic capacitor probably should be replaced as well.

 

[boroyon]

Thank you for comment. I want to repair the existing unit.
And I also think that it need to be replaced all eight electrolytic capacitors.
Today I get 28521-17120 (MH-6410) for HZJ81V(year 1993), and I saw the electric circuit.
However, the one I got today had a different circuit from the previous one, so it was not helpful.
Please see the circuit of 28521-17120.　I attached picture.

 

[45Dougal]

They really don't look that different, but the big resistor has a very different value so for sure they're not the same.
I would start by drawing out a circuit diagram for your board - it sounds like a big job but it won't take long.
Then maybe consider making up a test cable to test if it works. Some switches and bulbs should be enough to show it works

 

[boroyon]

Thank you for your big support.
If possible, please show me the circuit diagram of original pre-heating timer unit(28521-17100 for the glow plug of Landcruiser (1991 HZJ73v)).
If possible, please tell me the resistance values of the two burnt-out resistors in the first photo(unit No: 28521-17100：1991 HZJ73) might be able to repair the current original unit by myself.
By the way, I don't have much knowledge about electrical systems, but I can solder resistors and capacitors and replace them.

 

[boroyon]

I'm an amateur when it comes to electricity, so if possible, please explain in an easy-to-understand manner.

 

[45Dougal]

Id start at the connector block.
Draw a box with 13pins and work out what each one is connected to and add it to the diagram, then keep going until you have every component drawn.
You'll probably need to redraw it 3 or 4 times before you catch it all.
There will be a few mystery components but that doesnt really matter for now.
You'll have to look at your wiring diagram to work out what to connect it to in order to test it.

 

[boroyon]

Id start at the connector block.
Draw a box with 13pins and work out what each one is connected to and add it to the diagram, then keep going until you have every component drawn.
You'll probably need to redraw it 3 or 4 times before you catch it all.
There will be a few mystery components but that doesnt really matter for now.
You'll have to look at your wiring diagram to work out what to connect it to in order to test it.

　Thank you for support. I am amature about electrical cuicuit. Is it possible for me to take your instructions and understand them?　Please explain as much as possible so that I can understand the circuit of this unit（original pre-heating timer unit(28521-17100） and the value of the burnt two or one resistor.

 

[veiloctane]

you can actually scrape and measure with test leads to find the value