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Hey Guys I have a problem that I cannot figure out. Need help bad. Working on a 1999 Volvo S70 and the cooling fan is not working. I jumped the fan directly to the battery and the fan works that way. I replaced the relay with a used one but it still does not work. I checked the out put on the relay and I am getting 12V. This is making me crazy. Could it be the Yellow and yellow/white signal wire coming from the ECU. I checked these with DVM and am getting nothing (no voltage) at all. Does anyone think it may be the coolant sensor causing this? If anyone has a test procedure can you forward to me? Thanks.
Driveway
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Normaly there is a coolant temp sensor that tells the fan(s) to come on. you can do a resistance test on it and compare to specs. sorry I do not have the specs for this car.
Thanks for the starting point. I will also try to ground the signal part of the relay and check to see if the fans work.
Without seeing a diagram, I would think the signal wire would go to the low amp side of the relay, and the ECM would get it’s info to turn on from the ECT(s) as stated. Are you getting voltage there at all ever(from the signal wire)? And when you say you are getting 12v at the relay, which pin? The high amp in or out or etc..? Does the temp gauge work? It may run off a separate temp sensor, but if there are two, and one is bad, I would think that would throw a code. All else fails, you can run a switch in the cab and manually turn the fan on until you figure it out.
Hope this might help
http://www.bbbind.com/tech_database.htmlHope this may help. Schematic with temp sensor (C) not sure what size engine it is, you never stated it. This is for 2.3
Thanks guys, I am reading the voltage on the high amp out of the relay. The temperature gauge appears to be working fine. as the engines heats up almost to red the coolant starts to boil and I have to turn engine off. I am going to have another go at it today. I will review all of the schematics you sent. Thanks for that. And I will get back to you on the engine size. I will let you guys know how I make out later.
Driveway
I’m sure you have already but you did check all your fuses under the hood and in the car right?
When is the last time the car had a thermostat?
If your not sure just put a new fail safe thermostat in it to be safe and bleed the system of air.
The thermostats are easy to replace in these if I remember corretly.
Good luck and keep us posted.I just shot a video on this with another vehicle with a similar problem. A relay has 2 parts, the high amp side and the low amp side. The high amp side connects directly to the fan, you should be able to jump across those terminals and the fan should run, if it does then your problem is on the control or low amp side of the circuit. If it doesn’t run then check the wiring to the fan and to ground for the relay. As for the control side I didn’t look at the wiring diagram but normally the fan switch OR coolant temp sensor sends a signal to the PCM or a control unit and THAT is what grounds the control side of the relay to activate it. I ended up ohming out the wires going to the relay from the control unit, found them to be good, and ended up replacing the control unit which fixed the problem. Here is a video on testing relays that might also help you.
Hi everyone, just wanted to give an update on the Volvo. I have found that the relay and fan were actually ok. I had jumped the fan directly to the battery and it ran. next I had connected my Actron reader and watched the temp. data increase and it seemed to be consistent with the engine temp. so I kind of assumed it was ok so I moved onto the relay. I got the control signal at about 185F so i assumed the control side to be working as well. Then I checked the voltage on the relay out and it was around 12V. I then moved onto taking the ground wire off of the connector and grounded the fan side to body and guess what “it worked”. The problem was the black ground wire going somewhere “it looked to be under the ECU” so I did not mess with it. I then extended the fan ground to body and now the fan cycles on and off with no problem. The problem was not in the connectors themselves because I probed behind them. Thanks for everyones help and thank you Eric for the great videos as always. Hope this helps someone in the future.
Driveway
I don’t like running extra wires to fix something, in fact that circuit is probably ground side switched and if that’s the case you may be running the fan all the time which would not be good. Here is a video that I posted today on a similar problem that might better illustrate what I’m talking about.
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