Auxiliary Water Pump Stays on!

[Robou]

The auxiliary water pump is meant to prevent building up heat after switching off the engine by sustaining some circulation in the cooling system. There is quite some variation in how it is governed, depending on model and year. This is why you will find so many observations in this thread. When your car is a turbo, has no injector cooling and the chassis# is higher than 577284 the working is roughly as follows.

Relais(D) sends a +12V to the pump and has two sources. When it is activated the pump is connected to the drain of relais(B2) of the fuel injection system and when not activated to the temperature switch in the turbo housing. Both relais are activated bij the Jetronics ECU.

When the ignition is switched off the Jetronics keeps both relais activated for about 1 minute below 90°C engine temperature. During this time the pump is running through relais B2 and relais D. After 1 minute the activation of both relais stops and the pump is only connected to the other source of relais D, being the temperature switch. The weird thing is, that when the engine temperature is higher, the relais are not activated, I presume this is because in this case the developers expect the turbo temperature to be over 100°C and the pump coming in anyway through the switch.

This switch closes at about 100°C. So if temperature in the turbo housing is higher, the pump keeps running, getting its +12V from the switch. It prevents building up carbon deposits in the bearings.

Your observations about the the activity of the pump may be correct. It is just the "if not stone cold" which make me wonder. It means that at that time the Jetronics does not activate relais(D) and and other "cold" times it does. Relais(B2) is switched on anyway, something strange here.

Earlier designs activated the pump only after switching the ignition off. In your case it will be running whenever both relais are activated or the switch in the turbo housing closes.

[grafi]

The auxiliary water pump is meant to prevent building up heat after switching off the engine by sustaining some circulation in the cooling system. There is quite some variation in how it is governed, depending on model and year. This is why you will find so many observations in this thread. When your car is a turbo, has no injector cooling and the chassis# is higher than 577284 the working is roughly as follows.

Relais(D) sends a +12V to the pump and has two sources. When it is activated the pump is connected to the drain of relais(B2) of the fuel injection system and when not activated to the temperature switch in the turbo housing. Both relais are activated bij the Jetronics ECU.

When the ignition is switched off the Jetronics keeps both relais activated for about 1 minute below 90°C engine temperature. During this time the pump is running through relais B2 and relais D. After 1 minute the activation of both relais stops and the pump is only connected to the other source of relais D, being the temperature switch. The weird thing is, that when the engine temperature is higher, the relais are not activated, I presume this is because in this case the developers expect the turbo temperature to be over 100°C and the pump coming in anyway through the switch.

This switch closes at about 100°C. So if temperature in the turbo housing is higher, the pump keeps running, getting its +12V from the switch. It prevents building up carbon deposits in the bearings.

Your observations about the the activity of the pump may be correct. It is just the "if not stone cold" which make me wonder. It means that at that time the Jetronics does not activate relais(D) and and other "cold" times it does. Relais(B2) is switched on anyway, something strange here.

Earlier designs activated the pump only after switching the ignition off. In your case it will be running whenever both relais are activated or the switch in the turbo housing closes.

Thank you very much for the information! I do have turbo without injector cooling, but the chassis number is below 577284. (576343) (I dont know if its relevant, but the ECU is the "maroon" version.) Does it mean that I may have a completely different control of the pump? (I dont think so.) Anyway, I am not really familiar in electronic, so I will take the car to an expert to check the relais. Maybe it will bring some result. I also have a spare ECU, a "green" one from a later modell. ('96 440 Turbo) Should I replace it to see if it brings any difference?
Thanks again for your help!

[Robou]

Completely different. Now only the (different) relais(D) is responsible. As long as the ignition is switched on the relais can not be activated, so the pump shouldn't work. The relais has a timing device build in which is triggered as long as the temperature within the turbo is over about 95°C. The ECU and the engine temperature have no role in this. And even here variations are possible. There has been a lot of fiddling around. Sometimes the relais comes in anyway after switching ignition off for about 20 sec and, if temperature is still over 95°C repeats this 20 sec until the temperature is below 90°C, sometimes it comes in only when temperature is high and stays on for 10 min. after reaching the lower temperature. If applicable, also the temperature sensor of the injector cooling system is checked in parallel with the one in the turbo housing.

It is all very complicated and I wonder what good an electrician could do. Notice, that relais(D) has at least two types and indeed, the ECU should cooperate in certain cases. If you make a habit of switching things around you may very well louse up the situation. When you reread you may reconstruct how it should be in your situation. The chassis # I supplied is official, but don't be too sure it is correct.

[grafi]

Completely different. Now only the (different) relais(D) is responsible. As long as the ignition is switched on the relais can not be activated, so the pump shouldn't work. The relais has a timing device build in which is triggered as long as the temperature within the turbo is over about 95°C. The ECU and the engine temperature have no role in this. And even here variations are possible. There has been a lot of fiddling around. Sometimes the relais comes in anyway after switching ignition off for about 20 sec and, if temperature is still over 95°C repeats this 20 sec until the temperature is below 90°C, sometimes it comes in only when temperature is high and stays on for 10 min. after reaching the lower temperature. If applicable, also the temperature sensor of the injector cooling system is checked in parallel with the one in the turbo housing.

It is all very complicated and I wonder what good an electrician could do. Notice, that relais(D) has at least two types and indeed, the ECU should cooperate in certain cases. If you make a habit of switching things around you may very well louse up the situation. When you reread you may reconstruct how it should be in your situation. The chassis # I supplied is official, but don't be too sure it is correct.

I found the electrical shemes:
http://volvo480.northernscum.org.uk/files/91wiring.pdf
I guess page 18 and 19 is what I was looking for.
I have a question: The sensor B16 should be located somewhere on the turbo housing?
Thank you in advance.

[Robou]

I don't know what you found, it must be huge concerning my browser. Anyway, the temperature sensor is supposed to be located in the outlet hose of the turbo.

[grafi]

I don't know what you found, it must be huge concerning my browser. Anyway, the temperature sensor is supposed to be located in the outlet hose of the turbo.

Thanks, I will check it tonight.

The pages I referred to are these:

http://img3.tar.hu/kisgrafi/img/71795481.jpg#3

[Robou]

This is the situation officially from before '92. Only the engine temperature is used as reference. You claimed your car is from '92.
If your relais(D) has only 4 connections you will not find a temperature sensor or switch in the water outlet hose of the turbo. Only when the relais has 5 contacts a device will be found. This can either be a switch, when one of the contacts is marked 87a, or a sensor, I believe the extra contact then is marked TS. The latter type relais has some trigger inside depending on the resistance of the sensor.

Only when you are sure about how the car is equipped you can start wondering about what is going wrong, if so.

[grafi]

This is the situation officially from before '92. Only the engine temperature is used as reference. You claimed your car is from '92.
If your relais(D) has only 4 connections you will not find a temperature sensor or switch in the water outlet hose of the turbo. Only when the relais has 5 contacts a device will be found. This can either be a switch, when one of the contacts is marked 87a, or a sensor, I believe the extra contact then is marked TS. The latter type relais has some trigger inside depending on the resistance of the sensor.

Only when you are sure about how the car is equipped you can start wondering about what is going wrong, if so.

Well, the car's chassis number is 576343, it was first registered in '92 Germany, and the VIN reader says it is modell year 1992.
But according to the chassis number in the electrical shemes, the auxilary water pump system is pre '92. (and I did not find the L shaped sensor at all)
These pictures were taken from the original donor:
Picture 1
Picture 2
Picture 3

Well, now I am a bit confused, but I will check the realis(D).

[grafi]

it seems I have relay problem. Hopefully it will be solved this weekend.
Thank you Robou for the informations!

[Robou]

Volvo experimented a lot in switching the auxiliary waterpump. Any of the methods is quite complicated, timing can be done in the ECU (LH2.2) as well in the relais, multiple temperature sensors can be involved, even a temperature switch.
For a diagnosis it is important to know:
* Does the relais have 4 or 5 connectors. The latter has a connector labeled 87a, connected to a temp switch at the turbo housing.
* Does the car have injector cooling.
It would take pages to explain all of the possibilities. Answers would narrow it down.
Only if the temperature switch is present it is possible for the pump to run at ingnition on, if temperature is over 100ºC.
Providing your information is correct something is wrong. For your sake I hope your car has the switch, in that case it may have a short.