S/V/C 99 V70 GLT E-Fan

vvpete · 12-17-2020, 05:10 PM

Maybe I'm insane, but I just picked up a '99 V70 GLT, low miles, cheap, but many problems, and the first to address is the e-fan that is not working, no grounding to activate the relay.

Does anyone know where the ground originates? I get a constant 170k ohms, whether the temp is at or above operating temps, not getting a complete ground, which I would assume comes through the ECM when it see the temp rise/ rate-of-rise to turn it on. ECM failure?

New temp sensor and 87 deg t-stat, car runs fine otherwise, temps via OBDII show constant 87 deg F normal operating temps, using a manual switch on the fan.

dl242gt · 12-18-2020, 12:49 PM

My understanding is those fan systems are grounded by the engine ecu to activate the relay.

vvpete · 12-18-2020, 04:53 PM

Thanks Dave, yeah, pretty much all cars after '94 incl 940's have it switched that way.
I have schematics for up to '98 850 S/V70 cars and the '99 is completely different. I just wanted to know where the source ground comes from, the input to the ECU, so I can rule that out. It is most likely a bad ECU, or ECM as Volvo calls them in the later cars. I still haven't found which one does the fan circuit though.

ZVOLV · 12-19-2020, 12:53 PM

Consult a wiring diagram.

A quick test: find which terminal at the ECM grounds the fan. There should be a low and a high. Short each terminal to ground and the fan should come on. That will confirm wiring/relay operation and leave the fault at the ECM.

Or put a bi directional scan tool on it and operate the fan. And monitor the ECT data.

vvpete · 01-12-2021, 05:54 PM

Quote:

Originally Posted by ZVOLV

Consult a wiring diagram.

A quick test: find which terminal at the ECM grounds the fan. There should be a low and a high. Short each terminal to ground and the fan should come on. That will confirm wiring/relay operation and leave the fault at the ECM.

Or put a bi directional scan tool on it and operate the fan. And monitor the ECT data.

Yes, done that when I got the car, manual switch to ground it until I figure out where the ground fault is. My diagnostic tool can run real time graphic test of the CTS performance while driving, which holds a constant 80 deg when the fan is on and up to operating temp.

Fan works with relay grounded. ECM signals the constant idle circuit to engage when the CTS reaches 92-95 deg, in anticipation of the load from the fan, but still no ground through the ECM to the fan, as said, 170k ohms, not high or low found, as I would expect to find, so looking like the ECM is at fault. It throws a lot of bogus codes, too, but a reset everything is fine except the fan output.

This beast is an electrical nightmare, If it didn't run so well I would take it to the crusher.

ovlov760 · 01-13-2021, 12:05 PM

Have you tried unseating and reseating the ECU by any chance? Any evidence of burnt out pins on the ECU?

vvpete · 01-13-2021, 05:21 PM

Yes, did that, but nothing obvious.

ovlov760 · 01-13-2021, 06:48 PM

I would figure out what all the other fault codes pertain to and then take a look at a wiring diagram.

12-17-2020, 05:10 PM	#1
vvpete Board Member Join Date: Feb 2005 Location: Land of Enchantment	99 V70 GLT E-Fan Maybe I'm insane, but I just picked up a '99 V70 GLT, low miles, cheap, but many problems, and the first to address is the e-fan that is not working, no grounding to activate the relay. Does anyone know where the ground originates? I get a constant 170k ohms, whether the temp is at or above operating temps, not getting a complete ground, which I would assume comes through the ECM when it see the temp rise/ rate-of-rise to turn it on. ECM failure? New temp sensor and 87 deg t-stat, car runs fine otherwise, temps via OBDII show constant 87 deg F normal operating temps, using a manual switch on the fan.

12-18-2020, 12:49 PM	#2
dl242gt Happy playing the blues Join Date: Jun 2002 Location: S NJ, a suburb of Phila.	My understanding is those fan systems are grounded by the engine ecu to activate the relay. __________________ Dave, 1982 242 turbo. 338k miles. MVP coilovers and 3" exhaust. Flowed 405 with a V15. Cossie turbine housing with upgraded compressor housing. 90+, IPD remote oil filter. Some other goodness, too. Been lots of fun over 25 years. Restored in 2k. Now ready for a 2nd restoration. 1993 245 Classic, 430k miles, enem V15. IPD bars and chassis braces. Simons sport exhaust from Scandix. sbabbs ezk chip. Been a good road warrior. Genuine Volvo rebuilt leaky M47.

12-19-2020, 12:53 PM	#4
ZVOLV <Master Tech> Join Date: Nov 2002 Location: California	Consult a wiring diagram. A quick test: find which terminal at the ECM grounds the fan. There should be a low and a high. Short each terminal to ground and the fan should come on. That will confirm wiring/relay operation and leave the fault at the ECM. Or put a bi directional scan tool on it and operate the fan. And monitor the ECT data. __________________ No Start Thread

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12-18-2020, 04:53 PM	#3
vvpete Board Member Join Date: Feb 2005 Location: Land of Enchantment	Thanks Dave, yeah, pretty much all cars after '94 incl 940's have it switched that way. I have schematics for up to '98 850 S/V70 cars and the '99 is completely different. I just wanted to know where the source ground comes from, the input to the ECU, so I can rule that out. It is most likely a bad ECU, or ECM as Volvo calls them in the later cars. I still haven't found which one does the fan circuit though.

01-13-2021, 12:05 PM	#6
ovlov760 Board Member Join Date: Jun 2003 Location: Midwest - IL	Have you tried unseating and reseating the ECU by any chance? Any evidence of burnt out pins on the ECU?

01-13-2021, 05:21 PM	#7
vvpete Board Member Join Date: Feb 2005 Location: Land of Enchantment	Yes, did that, but nothing obvious.

01-13-2021, 06:48 PM	#8
ovlov760 Board Member Join Date: Jun 2003 Location: Midwest - IL	I would figure out what all the other fault codes pertain to and then take a look at a wiring diagram.