I've had this 1990 4-cyl turbo for three years, and I don't think the auxiliary fan has ever worked. The fan itself works when connected direct to the battery. And the relay seems fine, since I have swapped it out with several others including the suppressor relay and had no difference. So I suspect it's the push-in switch that is in the radiator. Are there any other components I should look at? Is there a timer?

 

1990 4 cyl turbo /what/ ? there were no 1990 240 turbos in the USA (car listed on your header).

on the earlier redblock turbos that had the mechanical fan AND an aux electric fan, I believe the electric fan was hooked up so it normally only runs if the AC is on, unless the engine was VERY hot, then it would run anyways.

 

Pierce:
Its a 780 turbo, which is generally same as 740/760. I guess the 245 is listed first in my garage so it appears above my post regardless of the vehicle I am seeking help with.

I will check out the operation with AC on--I don't think I've ever checked that. Presumably it needs coolant temperature to activate the switch also, so not sure I'll get anything conclusive until warmer weather.

Thanks for the suggestion.

Rob

 

Wow! So you have a 780 Bertone Coupe? Please post pictures here. They look great! Think you got to change that switch.

 

unluckily, I do not have 780 greenbooks, so I can't check the wiring. I know there's a LOT of differences. I could tell you how its wired on a 1991 740/940 or a 1991 940SE(960 turbo), but the 780 was a unique beast. AFAIK, it was forked off the 760 design when it first came out, and not updated nearly as much as the main line 760's. early 760s were wired more like 740s', but some time in the mid-late 80s, they did a major upgrade/change of the 760 harness, while the 740 (and 940) continued with the original design.

on the 1991 940SE ('960 turbo'), the electric cooling fan is controlled by relay 2/11, and that relay is activated by EITHER the 7/14 thermoswitch, or the a/c control unit. relay 2/11 is under the hood on the left side suspension tower, to the right of the power steering reservoir and behind the ABS. thermoswitch 7/14 is on the top/right side of the radiator. if you short that thermoswitch, the fan should come on, if the ignition is on.

on the 1991 740/940, the cooling fan is controlled by relay 131, which is activated by pressure switch 82, OR the ECC control unit (if the car has ECC), OR thermal switch 224, all of this is on fuse 9 and the ignition switch. relay 131 is on the RIGHT fender near the suspension tower, pressure switch 82 is on the AC line near the firewall, and the thermoswitch 224 is somewhere on the radiator (drawing is totally ambiguous, probably top right side). shorting either the pressure switch or thermoswitch should activate the fan if the relay is good.

I do have the VADIS parts catalog that covers a 1990 780, it doesn't show the pressure switch in question on the 740/940 (there's another pressure switch on the a/c reciever/dryer, afaik that one enables the AC compressor to run).

ps. I owned a 1989 780 Bertone (V6) for 6 months in 1989 (yes, as a new car). put 20k miles on it in 6 months. sweetest new car I've ever owned. wrecked it

 

It is merely an overheat fan and the radiator switch has an ungodly high threshold; that's why you haven't had it run.Honestly, on a turbo car, I'd be strongly tempted to remove it altogether. It impedes air flow IMO. If you have minor cooling issues, after pulling the fan, loosen the mounts on your condenser and wedge it forward on the bottom to where you have about a 1" gap and then snug it down. Your radiator is like a red headed stepchild...gets whats left after the aux fan, condenser and i/c get their share.

 

The first sentence in Swift's post is absolutely correct. I can't even count how many people I have argued with that insist that the electric fan should be on whenever the A/C is on, because that's the way it is with most other cars. Not so.

 

Thanks for the inputs. Perhaps I don't have a problem at all.

The relays (auxilliary cooling fan and radio suppression relays) are identical and co-located between the battery and the left headlight on the 780 turbo. I have exchange these relays (and a third one) with no apparent effect on fan or engine operation, so that seems not to be the problem. I can run the fan with a direct connection to the battery so the fan itself works.

I don't get any fan action when I shunt between the connectors for the radiator temperature switch whether ignition is on or off--Pierce, you seemed to suggest that this should make the fan run; is this test definitive? I have a new push-in switch and grommet on the way, but don't want to mess with it unless it seems likely to make a difference. Also, how is the switch removed? Just brute force? Or is there some secret trick?

 

well, I don't have the schematics for a 780, so I can't say for sure that would make it run. on the 740 wiring diagrams I do have (1991, 1992), and the 1991 940SE (760/960 turbo), yes, with ignition on, shunting that switch should have started the fan, if the relay is functioning.

next test, I think, would be to find that relay, pull it out, and put a test light across its coil side, and when you shunt hte thermoswitch, that test light should light. if so, shunt the relay switch side, and the fan should spin. if so, you likely have a bad relay.

 

I wired in a relay so that when you turn on the AC the fan comes on. It will also still work from the temp sender in the rad. My fan never cam on during normal use (89 , 740) and when I had to replace the condenser I found the fan was frozen so I replaced it. Also found the 134 conversion would cool better when the fan was running with the AC on. 330K and still going

 

Yeah, I think I've actually seen instructions on how to do that on Brickboard or somewhere and it's been on my to-do list simply because you are always going to get better cooling with better airlflow over the condenser, no matter which refrigerant you're using. Down here in TX, when I'm stuck in rush hour traffic in my 745T in August with the AC on, the fan will come on occasionally and I can see the temperature drop on the dial thermometer that I always have stuck in the vent. Can't imagine why Volvo didn't wire them like every other car. Guess it doesn't get that cold in Sweden..

 

My 89 740 Turbo wagon's Aux fan rarely comes on too. It's just controlled by a switch in the radiator. So I'm just joining the ranks here. Mine will switch on only on really hot days when the car idles for a bit. Here in the dry Utah summer I hear it more than at home in West Virginia. But still it's not often.

But the most interesting thing that I have to ad is the fuse in my car, #7, melted down in the fuse box and never ran when I was a younger. It wasn't until I was in high school and was fixing things that I ever got it to work again. I put in an auxiliary fuse slot in place of it. Then a year of so later the switch in the radiator melted and caught fire. Then I put in a switch from a junkyard car and haven't had a problem since.

 

my 92 turbo has the dual speed electric only fan, this seems to run pretty much all the time, although there are both low and high speed switches. low speed is controlled by (low-pressure-switch OR ecu-out-1) and high speed is controlled by (high-pressure-switch OR ecu-out-2 OR high-temp-switch)

now, I dunno under what conditions the ECU fires its two fan outputs, but the fan doesn't seem to come on when the engine is cold, only after its warmed up a bit. I haven't noticed mine come on high speed very often at all, but I live where the temperatures are quite moderate, and I also try to give the engine a chance to cool down on the last mile before parking, and resist the temptation to blast up the steep hill I live on

 

Changed out the thermoswitch today, with no apparent performance change. I haven't had cooling problems so I might be chasing a red herring--maybe I should leave well enough alone.

I was under the impression that the fan would keep running after shut-down if the thermoswitch exceeded its temperature setting, but I guess it doesn't work that way--it just provides extra airflow if the ignition and the thermoswitch are activated, and so maybe just in hot weather when going up hill in slow traffic with A/C running. I have a Chiltons schematic for a 780 B230FT for what its worth, and it shows no connection to any A/C pressure sensors. It test a few other things but probably back off until the summer. I keep it garaged and this time of year bring it out only in fine weather to keep the battery charged.