1998 V70 Cooling Fan Problem

jgerhard45 · Post by **jgerhard45** » 28 Dec 2010, 18:48

I’ve had a problem with my 1998 V70 surging at idle when warm. If I disconnect the IAC it runs fine but idles high. With some troubleshooting it appears the cooling fan is not turning at low speed, it does turn on high speed at about 217F but that’s right where it trips the check engine light. I also have a 1997 850 and the fan turns on low speed at 170F. I have replaced the thermostat and coolant temp sensor. I have swapped a known good relay between cars and the fan still does not turn on at low speed. I have jumpered 12vdc to the fan and it runs fine both low and high speed. Does anyone have an idea why the fan would not turn on at low speed?

Post by **phils94850** » 29 Dec 2010, 01:46

the fan coming on has nothing to do with "speed," It only comes on when the temp reaches a certain point or you turn on the A/C.

instarx · Post by **instarx** » 29 Dec 2010, 08:38

phils94850 wrote:the fan coming on has nothing to do with "speed," It only comes on when the temp reaches a certain point or you turn on the A/C.

I'm pretty sure he is means his fan has a low and high speed, but the low speed doesn't work.

Post by **jblackburn** » 29 Dec 2010, 08:42

The only thing I can think is that your fan relay isn't getting the signal to turn on the fan.

I think my next step would be to remove the ECU from the box and clean the pin contacts on both boards. Perhaps one is corroded up and the signal isn't getting across.

jgerhard45 · Post by **jgerhard45** » 29 Dec 2010, 10:17

If I'm reading the schematic correctly the ECU gives the high and low speed coils in the relay a ground to turn on the relay, is that right? I noticed that the box for the ECU has an upper and lower section, I assume that there are a number of electrical connections in the botton section since the schematic shows ground connections there. Is there a need to remove the top section and look for corrosion there?

Post by **Ozark Lee** » 30 Dec 2010, 08:07

The cooling fan relay is a known weak link. Remove the center connector with the yellow wire and the yellow/white wire and ground each of the terminals on the relay (one at a time) and see what the fan does. One should trigger low speed fan operation and the other should trigger high speed. The relay is mounted below the top of the fan shroud.

Off the top of my head I can't remember which wire triggers which fan speed but it is important that both speeds work.

...Lee

jgerhard45 · Post by **jgerhard45** » 30 Dec 2010, 09:28

I've done that and the fan and relay both seem to work fine. I've checked the wiring for continuity from the connectors back to the ECU and all seems to be fine. A driving test yesterday showed that the fan comes on intermittantly. when it runs as it should the car runs fine but when the fan does not turn on the temp goes to 217 and the idle starts surging and sets a CEL. It looks to me that the ECU is bad and not turning on the fan. I did find a badly leaking injector recently that has now been replaced. Has anyone heard of a leaking injector causing problems with the ECU.

Post by **Ozark Lee** » 30 Dec 2010, 17:44

The fan runs very little on low speed - on my first 850 it had me kinda freaked out since I was used to the blower running most of the time the car was running on other makes. That said, you seemed to indicate that the car got hot (temp gauge above the 3:00 position) before the blower kicked on.

On my '94 I had a similar problem and it was the connector from the ECU to the cooling fan relay. I gave it a shot of contact cleaner and unplugged it a few times to clean any residual crap off of the contacts and it has worked fine ever since in my case.

I never had a situation where the car was actually running hot and the fan wasn't coming on but that is certainly a cause for concern.

...Lee