Gen I Electric Fan not working, Any tips or ideas appreciated.

[ACELLR8]

Been trying to figure out why my Electric fan on my 95 Viper is not coming on.

So far this is what I know, when I jumper accross the relay connecter with a wire the fan comes on, so I would believe that is telling me the Fused link is good and that the fan is good. I have so far replaced the relay and the coolant temp sensor. Still can not get it to come on when the temp goes up.

Any tips or help would be greatly appreciated. I am scratching my head on this now and would like to get it back on the road as this is the time to be driving.

Thanks in advance,
Ed

 

[pollard4286]

Roe Racing sells a fan control module kit. You wire it in and you control what temp you want the fan to come on. That might be an easy fix, if the fan is still working when you jump it. I have one on my 95 and it works great. However my fan was working fine, I just wanted it to come on at a lower temp, to help the car stay cool. The kit was around $150.00. I think.

 

[jdeft1]

Temp sensor.... Have a closer look.

 

[Allan]

No direct experience with 95 Viper platform.
But, assuming it's the same as other Chrysler vehicles in respect to engine control and sub-systems (most of that stuff is),
PCM has control of fan operation.
Input is from engine coolant temp sensor. No other 'fan switch/sensor' like some vehicles have. -the Roe kit converts it to such a system.

Chrysler fan on temp is 210-211 degrees F.
Fan off at 199-201 F..........depending on vehicle.
I would assume the Viper is the same or at least close to this.
Scan tool with data stream capability required to correctly diagnose PCM control of cooling fan circuit.
(need to see what temp the PCM thinks the engine is, and if it is attempting to turn on the fan) -PCM controls the fan relay by grounding the pull-in circuit. ....relay pins 85/86 are the pull-in circuit.

Here's one quick check you might do....remove the relay, with a test light, make sure you have 2 of the terminals hot with the key on.
Pin 30 should be hot at all times, as it's battery feed. Pin 85 or 86 will be ignition switched key power.
Pin 87 is wired to the fan motor.
If you don't have both batt and ign power available, the PCM can't turn on the fan. -fix the voltage supply problem.

If the fan runs with a jumper across pins 30/87 where the relay plugs in, it is not a ground problem anywhere.
It's either a bad relay, no key power to the relay, or the relay control 'driver' in the PCM is bad, or in-accurate coolant temp sensor lying to the PCM.
With no poor running problem ( too rich / too lean -surging/rolling idle and whatnot, probably not a sensor issue )
-Coolant sensor affects fuel trim. ......runs the same as it always has, unlikely to be the sensor.

Are you sure it's really running hot and not just a gauge discrepancy problem?
.....I have seen bogus temp gauge readings make you think you have a problem that isn't there.
Compare scan tool data stream temp with temp gauge and also non-contact thermometer reading of engine.
Should all be marginally close. -within about 5 degrees.

Hope this helps...........

 

[ACELLR8]

Allan, Thanks soo much for the info that is the what I needed to know is where the pins on the relay went. I am gonna check the things you mentioned tonight and see how I make out.

Thanks again! Ed

 

[ACELLR8]

Allan

I checked the pins last night as you mentioned with a volt meter. Here is what I found. I found that pin 86 has 14 volts when the ignition is on, pin 30 has no power at any time. The fan kicks on when I jumper 86 to 87q or 87 with the ignition on. I then checked the fusable links over on the drivers side by the remote jump post. I checked for 12V on both sides of the link and all checked good.
I noticed that the wire that pin 30 is on is green, i could not find a fuseable link with the color of this wire. I even checked the back of the connector where the green wire for 12V and nothing. So it appears the "hot all the time" wire might be bad. Any idea if this has a fuseable link and where it is?

Here is a pic of the fusable links that I checked. Not sure if these are the correct fuseable links.

Thanks again for the info and help!!

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[Allan]

Hmmm. Not good to jump 86 to 87 for very long, if at all.
85/86 are control circuits, 87/30 are load circuits.
Wiring and voltage supply source for 86 are not heavy enough to carry the load of a fan motor.

It would seem that no voltage at pin 30 is the problem.
Lack of experience with your particular car makes me ask if there is a fuse for the cooling fan, not a fuse link.

If this becomes a wild goose chase looking for a needle in a haystack, you could always run a fused alternate wire to the pin 30 wire.
If you find the factory fuse or link, and it is good (has voltage), then there is an open circuit (break) in the wire between the fuse and the relay connector.
Easier to run the alternate wire I suggest than to dissect the harness until you never find the problem with the wire.

 

[Allan]

Just looked up power distribution schematic.
Shows fuse link for voltage supply, green/yellow and gray wires after links from heavy red wire.
Green/yellow to fan relay load circuit, gray to ignition switch.

If there's voltage in the green/yellow wire after the link, schematic shows a splice/connector between the link and the relay connector.
Look for that to see if it's unplugged or corroded.
If not, or you can't find it, run the by-pass voltage supply.

 

[ACELLR8]

Allan, Thanks again for the info. I am confident tonight I will get it resolved with your information. I was kind of thinking what you were about running a new fused wire to the back of Pin 30.
Your help is much appreciated! I will keep you posted and this thread posted!

Ed

 

[ACELLR8]

Ok worked on this again tonight, now I am convinced I am really ******** or had too many gin and tonics

I ran a new hot fused wire to the remote battery post to what I believe is pin 30. All seemed good until I put the relay in and the fan came on instantly even without the key in the ignition. Maybe I am reading this relay wrong or something else is hosed. I assume that pin 30 is the bottom verticle connector on the relay, because it has a small number 30 next to it. On the back of the relay connector it is the green wire with a white stripe. I did not see a green yellow wire.

Here are a few pics of the relay and what I believe to be pin 30.

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Here is a pic of the wire i cut and where I attached my new hot wire.

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Here is a pic of the relay diagram from the relay.

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[Allan]

Hmmm.

Check the relay for continuity between 87 and 30 with it unplugged
If it has continuity like that, the load side of the relay is shorted to itself. the relay is defective
Leave the alternate power feed on the car, and replace the relay.

 

[ACELLR8]

I just went home and grabbed both new relays and checked. I have continuity between Pin 30 and center pin 87Q. No continuity between Pin 30 and Pin 87. I hope I am reading these relay numbers correctly. Does my drawing above of what pins are what match up with what you believe they should be?

Thanks again for the help!!

Ed

 

[Doug Supercharged Vipers]

Dear Ed,

I already see part of your problem and it's not where you are looking. If you have some free time to call me today I'll walk you though it.
No strings attached of course!

Best regards,
Doug Levin / 954-9DLM (9356).

 

[Allan]

.....................................................

What's up with it.......

 

[ACELLR8]

Ok well I finally got a chance to look at this tonight late after Kids soccer games, homework and getting them to bed.

I think I finally will have to admit defeat by 1 95 Dodge Viper. Doug I checked everything you mentioned and really did not see any corrosion. I did learn that at the main cabin connector a few wires were already replaced, must have been done under a warranty job or while the first owner had the car.

I also learned a little more about how this circuit works. I did a continuity test between Pin # 87 (light green wire) to the fan (right at the fan) and this pin is the high speed fan, pin # 87Q (dark green wire) is the low speed fan. I also jumpered it and noticed the different speeds. So this explains why when I plug the relay in with Pin 30 hot all the time the low speed fan comes on. I have continuity between 30 and 87Q which looks like the normally open position.

Allan thanks a lot man for the help and explanations! I would have been lost if not for the information you provided on how this thing works. Doug thanks for reaching out to me and the pointers to check, nice chatting with you on the phone as well.

At this point I think I am going to order the Roe Racing fan kit and be done with it as well as get the benefits of the fan coming on earlier.

Thanks again guys and I will keep you posted if I figure anything out tonight while dreaming about this damn fan.

Ed

 

[Allan]

Fan tastic.

We're missing some other gremlin upstream somewhere obviously.
There must be another relay before that one, that the PCM turns on to provide the pin 30 voltage.
Then the relay we are obsessively checking is to control fan speed.

Rather than losing any more sleep over it, I think the Roe kit is a good idea.
Nice to have that ace in the hole.