1991 940 Relays running hot!

[przeski]

Hello,

I've got 1991 Volvo 940 with B200E engine.

My problem is, that in last two months, my pump relay was burned twice. So now I monitor it's temperature while driving, and realized, that front lights relay also gets hot. And I mean hot. After driving for a while it's hard to keep finger on any of these two relays.

My local mechanic said, that the relay tray was burned and he replaced it. But not the individual sockets, just the main board. Now I'm really worried, that pump fuel relay will burn again and car will stop in the middle of way. I do have a spare one if this happens, but what if it will burn also?

My mechanic also said, that he measured the pump current and it seems to be fine.

And about the lights relay: I replaced it with new one, and it also gets hot, even when I will pull out the lights fuses - so I guess there is a problem with control circuit - not the load.

Do you have any ideas what cause the problem? I would also appreciate any advices or manuals how to measure and check what is wrong.

I attached photo of my relay socket. The pump relay is the green one, and the front lights relay is the metal one with letter K
(2nd from the left).



Thank you!

[lummert]

Is there a chance that the alternator could be overcharging?

[przeski]

Is there a chance that the alternator could be overcharging?

What do you mean exactly ? Can you propose any measurements or checks?

[93Regina]

relay was burned twice...mechanic..said...pump current...fine.

I assume you mean the relay's spade terminal was burned, and in this process, the relay can get hot. Hence, your terminals may not be making good contact with each other. Was this burning on feed side (power), or on output side to pump/lights?

Either you need to cut out the area with bad wiring and female clip, and then replace it with new wire/clip, or just buy a Bosch Relay with a wiring plug and use these for pump/lights.

[przeski]

relay was burned twice...mechanic..said...pump current...fine.

I assume you mean the relay's spade terminal was burned, and in this process, the relay can get hot. Hence, your terminals may not be making good contact with each other. Was this burning on feed side (power), or on output side to pump/lights?

Well... I'm not sure that the spade terminal was the heat source. But who knows... Maybe it is worth to check. See the images below.

Burned original relay (sorry for the poor quality):


Burned replacement relay:



In both cases was burned the pin number 30. In original also 87.

[93Regina]

In both cases was burned the pin number 30. In original also 87.

Terminal 30 is the battery-powered input, and terminal 87 is the "switched" outgoing power (lights or fuel pump here).

Problem is:

1. Terminals were not making full contact with each other

2. Crimped terminal wire is not making full contact with terminal crimp.

Solutions:

1. Solider in a new short jumper wire with a new terminal on other end, for both sides (30 & 87)

Note - I have not seen your vehicle's wiring diagram...see next post

[93Regina]

From looking at Volvo's diagram I have, that relay shown is activating fuel pump and fuel injectors. So, two different solenoid circuits are there.

Fuel Injection Circuit - This supplies power to injectors, IAC, AMM, and radio suppressor relay.
Fuel Pump Circuit - Power to fuel pump

The schematic does not show terminal numbers corresponding to that relay posted, but here is how I think it is. If I used my test light and applied power, I could figure it out.

30 - Fuse #31 is used to power terminal 30, and this terminal should have 12 Volts when ignition key is on position, and maybe off position. I would have to trace diagram back further to know...but if there is 12 volts there always, then its hot all the time.

87 - Since terminal 87 was burned, this should represent fuel pump side most likely; if you apply power to the female terminal side, I think you will hear fuel pump energize.

87b - Most likely Fuel Injection Circuit - If power is applied to this terminal, your IAC/AMM/Injectors, and radio suppressor relay should have 12 Volts.

31b and 31 - Both are a ground signal when LH ECM activates them. I think 31b grounds when fuel pump is activated, and 31 grounds when ignition key is turned to on position. If you have a logic probe, you can turn on ignition, and see if a ground exists on terminal 31.

15 - I think its a power loop back...I would have to test to confirm

A Bosch Relay setup could be done, but I would try first to renew terminals 30 & 87....if its possible to access those terminals on back side of that fuse/relay/etc panel

[przeski]

A Bosch Relay setup could be done, but I would try first to renew terminals 30 & 87....if its possible to access those terminals on back side of that fuse/relay/etc panel

Ok. So just bypass the socket by adding pieces of thick wires between wires from tray bottom and connecting it directly to the relay? I'll try to do it on Saturday and I will let you know it if it helped.

Anyway, thank you for answer.

[93Regina]

Bosch Relay setup could be done

I would have to evaluate 31b and 31 terminals; I believe they are the ground signals from ECM which activate each relay.

I would never run the fuel pump(s) hot when ignition key is turned on.