My new 1992 M998 Avenger

[springer1981]

Time Delay Module

Theory of Operation:
24vdc power is supplied to the TDM on wire 583 (Red in picture) and passes thru the TDM to the Cadillac Valve also on wire 583. Ground is supplied to the TDM on wire 93 (Black in picture). The Ground circuit is interrupted to turn On and Off the Cadillac Valve thus disengaging and engaging the Fan Clutch respectively.

24vdc on wire 458 (Yellow in picture) of the TDM turns OFF power to the Cadillac Valve disengaging the Fan Clutch (no cooling). When the coolant temperature rises and exceeds the Fan Temperature Switch threshold the circuit OPENS removing the 24vdc from wire 458 (Yellow) of the TDM turning ON the Cadillac Valve engaging the Fan Clutch (cooling the engine).

When the throttle is pressed 75-100%, to accelerate, the Fan Cutout Switch is activated (Closed) turning ON 24vdc to wire 315 (Green in picture) to the TDM activating the 20 Second Time Delay. There are two possible outcomes. (One) If the fan clutch is engaged, cooling the engine, the TDM disengages the fan clutch for 20 seconds allowing maximum power for acceleration. OR, (Two) if the fan clutch is already disengaged, it will not engage for 20 seconds even if it's triggered to turn on by the fan temperature switch.




My Time Delay Module is defective. Today I tested it and nothing turns off the power to the Cadillac valve so the fan clutch is always disengaged and not cooling the engine. I replaced the TDM and Cadillac Valve a few years ago when I rebuilt my frozen fan clutch. https://www.steelsoldiers.com/threads/my-new-1992-m998-avenger.184818/post-2358901 Since that time the cooling never worked correctly (overheated). Prior to rebuilding the fan clutch it was frozen (engaged) and always cooling. I had replaced everything but the fan temperature switch and I thought that was the "smoking gun" in my last post. The temp switch did not fix the overheating. For the last 4 years I just ran with the TDM unplugged since that forces the cooling system to work, albeit all the time.

Today I tested the TDM after studying the circuit to figure out how it all worked. Here is the process I used to test everything. The only tool required is a VOM meter.
1. Disconnect 2 wire connector from Cadillac Valve Solenoid.
2. Put Volt meter on connector terminals coming from TDM and turn ignition on, should read 24vdc
3. Disconnect either wire on Fan Temperature Switch and Volt meter should drop to 0vdc
4. Press throttle to floor, meter should read 24vdc for 20 seconds and return to 0vdc
If any step fails, the TDM is bad. Reconnect wire to temp switch.

My new TDM is on order, I'll let you know how it goes.

 

[Milcommoguy]

I am not so sure the explanation / theory is correct. I might not grasp how the term engage or disengage is being use here. Tobash how does it work? HELP.

If at any time the Cadillac valve solenoid is 24 volts energized, the fan is disengaged. This is part of the fail safe design for cooling. If the kick-down switch at WOT is closed for the moment, the TDM is triggered applings 24 volts to solenoid for 20 seconds again disengaging fan. If fan was already disengaged (no 24 volts to solenoid, cycling normally in a cooling period) you get 20 seconds of nothing.... to go WOT fast or tip toe into the water.

I think your TDM is shorted (pulling a ground) with 24 volts all the time to solenoid. OR the temp switch is open. Both easy to check.

( power on does NOT mean fan ON)

The test is to pull the solenoid valve two wire plug = Fan lock up / cool OR pull one of the Temp Switch wires = Fan lock up / cool.

Just left Costco and it was a ZOO.... so I might not be thinking clearly.

If I got this wrong please don't send the "AVENGERS" after me. Drop my shield at Costco fighting off the crowds, CAMO

PS... The HIGH price REM Products is the ONLY way to go, unless one want a BIG headache and two Chineeesee TDM modules.

AND section 1 and section 13 IS THE BIG TEST of this link > https://gear-report.com/wp-content/uploads/2017/03/HMMWV A1 Troubleshooting.pdf <

 

[springer1981]

First, thanks for the reply. I believe we are on the same page on all points.

If at any time the Cadillac valve solenoid is 24 volts energized the fan is disengaged. This is part of the fail safe design for cooling. If the kick-down switch at WOT is closed for the moment, the TDM is triggered applings 24 volts to solenoid for 20 seconds again disengaging fan. If fan was already disengaged (no 24 volts to solenoid, cycling normally in a cooling period) you get 20 seconds of nothing.... to go WOT fast or tip toe into the water.

Today I tested it and nothing turns off the power to the Cadillac valve so the fan clutch is always disengaged and not cooling the engine.

To clarify I have 24vdc at the cadillac valve at all times when everything is hooked up. at that point the fan clutch is always disengaged or not applying power to the fan to cool the engine.

When the throttle is pressed 75-100%, to accelerate, the Fan Cutout Switch is activated (Closed) turning ON 24vdc to wire 315 (Green in picture) to the TDM activating the 20 Second Time Delay.

We are saying the same thing just differently.

I think your TDM is shorted (pulling a ground) with 24 volts all the time to solenoid. OR the temp switch is open. Both easy to check.

Exactly the problem. The TDM always supplies 24v to the cadillac valve solenoid.

Today I tested it and nothing turns off the power to the Cadillac valve

We are saying the same thing and I believe you understand the problem 100%

This statement baffles me " My Time Delay Module is defective. Today I tested it and nothing turns off the power to the Cadillac valve so the fan clutch is always disengaged and not cooling the engine. " ( power on does NOT mean fan ON)

Power to the cadillac valve disengages the fan clutch. Power on=Fan cooling OFF.
Same page just different wording.

The test is to pull the solenoid valve two wire plug = Fan lock up / cool OR pull one of the Temp Switch wires = Fan lock up / cool.

I have been running it for 4 years with the wires pulled to force the Fan "On" cooling the engine.

For the last 4 years I just ran with the TDM unplugged since that forces the cooling system to work, albeit all the time.

Just left Costco and it was a ZOO.... so I might not be thinking clearly.

If I got this wrong, please don't DIS me, CAMO

AND PS... The HIGH price REM Products is the ONLY way to go, unless one want a BIG headache.

REM is the only NEW manufacture part I would consider. I did however have an old NOS USA manufacture part of the same quality that I just put in. It is an Original suppler to the military and not Chinese junk.

I would never DIS you and always invite any constructive and information replies. I appreciate you taking the time to reply. I know my description might be hard to follow but we are on the same page.

 

[Milcommoguy]

First, thanks for the reply. I believe we are on the same page on all points.





To clarify I have 24vdc at the cadillac valve at all times when everything is hooked up. at that point the fan clutch is always disengaged or not applying power to the fan to cool the engine.





We are saying the same thing just differently.





Exactly the problem. The TDM always supplies 24v to the cadillac valve solenoid.





We are saying the same thing and I believe you understand the problem 100%





Power to the cadillac valve disengages the fan clutch. Power on=Fan cooling OFF.
Same page just different wording.





I have been running it for 4 years with the wires pulled to force the Fan "On" cooling the engine.








REM is the only NEW manufacture part I would consider. I did however have an old NOS USA manufacture part of the same quality that I just put in. It is an Original suppler to the military and not Chinese junk.

I would never DIS you and always invite any constructive and information replies. I appreciate you taking the time to reply. I know my description might be hard to follow but we are on the same page.

Yea... I had to reword the "DIS" thing... making a funny as I interpret the text / logic. This simple system is backwards logic to the way many think? The module is shot (your black wire to ground, a solid state part let the smoke out) or the low side of the solenoid coil shorted (internally) to ground, (could happen?) or ??do you have a 3 speed transmission?? a stuck closed Kick Down switch. You would with never get to third gear.

To not blow up another TDM... study up on section 13. Make sure the solenoid meets resistance spec's and either coil lead is not showing resistance to valve case. It can happen with time, heat, moisture, rust... (they run warm to hot). Don't worry bout the EMF diode shown on diagram. They don't exist, but should IMO. (ripped a few apart, never found one)

Go back and re-read it, LOL

Yea... OH I said that. It all fun and grease, CAMO

No super heroes died or were launched into space... never to return in this thread. Where's the "T" man when one needs back-up ?