Need some advise on my 34. Running a Spal electric puller fan and I have had to replace the relay once and now it has failed again. Has only about 40 hours run time on it. Bad fan? Bad relays? Love to go to a standard fan but space is really limited on the front of the engine. Any ideas on diagnosis and or fix is appreciated.
Do not go without a relay ,Is your relay large enough for the amp load? if so I would make sure grounds are good. I have run relays for years on race cars and street cars and never had one burn out. Does the sending unit trigger it or do you do it manually? If so maybe the sending unit is not heavy enough electrical wise.
You need a continuous duty relay. So something like a horn relay won't work. It's fine if only used for a second or two. I have several continuous duty relays on my car. I'll look up the NAPA number and post later.
Whose relay? I haven't had problems with Bosch or Tyco - cheap auto store ones might not be too good (not saying that that's what you're buying). Here is my experience with the Spal 16" electric fan during 10 years as a NASCAR mechanic who was responsible for building wiring harnesses for quite a few racecars: Measured inrush amperage draw 36-37 amps for less that a half second, normal operating draw 16-17 amps afterward. The wiring run from a quality (Honeywell or Eaton) Milspec switch to the fan was a 14 gauge (that's right, 14 gauge) aircraft quality wire (fine silver stranded) of approximately 100" and a 14ga ground to the car chassis of about 24". NO RELAY (although there was a thermal reset circuit breaker in the hot wire). Never had the breaker trip or a wire burn up. Had one failed Spal fan in about 150+ installs and over 350 races. I would think that if the sending unit was not heavy duty enough, it would just not pull in the relay (the relay coil should only need less an amp to be pulled in). So it should not fail the relay via the coil. If the relay is a common 30 amp, the 30 amp rating is for the unswitched contact (N.C. 87a) and the rating for the switched contacts (N.O. 87) is only 20 amps. This may be the fail point due to the inrush amperage spike.
I would say the relay is too small for the fan...you need to go bigger. A minimum 50 amp may work.But it is the same price for a 70 amp...........
Go- with 70 amp relay-starting current may be too much for your current relay. See crusty 40's comments above--have found similar amp readings on start and run modes.
Another possibility is the fan short cycling and burning up the relay contacts. IOW, the sending unit brings the fan on, engine cools by 5* and the fan shuts off, rinse and repeat on and on. DC current is really bad to arc across the contacts when the relay opens, several times worse than AC current, and the higher the amperage the worse it will arc.
Very possible, metlmuncher. The racecar fans were manually switched by the driver when needed, not on a temp. sender. The constant cycling could be the culprit, especially if the offset (temperature between on and off) is narrow (like 5* or so). Probably needs to be at least 10*. If it drops 10* and then needs to cycle again shortly thereafter, something else is wrong with the cooling system (unless you're pulling a long grade).
If you need to prevent the relay points from burning up, install a capacitor across the points, much like your breaker points for the ignition.
Appreciate all the input. Wife and I were out last weekend on a 100 mile cruise and five minutes from home the temp. gauge spiked to 225 ! Fortunately it happened on the way home. No long hills and mostly highway speed so short cycling shouldn't be a problem. Usually runs at 195 degrees when working whether cruising or driving around town. The fan is thermostatically controlled but I have a switch to bypass the thermostat for running the fan constantly. Jumped the fan wires and fan runs. Its the relay. I have an inquiry into the Spal tech dept. but no reply as of today. The relay was part of the original Spal fan package and had thought this was adequate but unaware of the amperage rating. I suspect the fan may be bad but have to check actual amperage draw vs rating on relay. The thought of replacing the fan is daunting. Have to remove the grille,radiator,fan shroud etc just to get to the fan.
Anecdotally, the wiring is by EZ Wire, complete harness front to back. It's an all steel car but I guess adding additional grounding won't hurt.
I would think the relay that came with you kit was a cheap one from c*#+a. Up it to a quality unit with more amps and you should be fine. A sending unit is nothing more than a ground when temperature reaches a set point for the sender.
Call Cooling Concepts and spend $260. Run your power wire to the relay run the other wire to the big terminal on your alternator. Install the heat sender and wire it to the relay. Keep it simple and you'll solve your fan problem.
I have had several 30 amp relays over heat and stop working on my electric fan- they were bosch ones that I pulled out of cars in the junkyard. I finally bought a 70 amp and Havent had a problem, I upped the wire size for the power and made sure to have a really good ground. If you have bad grounds they can cause all sorts of problems.
Again, thanks for the input guys. Just got off the tel. with Spal tech. and may have solved problem. When I installed the temp sending unit in the block I used teflon tape on the pipe threads. Obviously, in hindsight, this is incorrect. The threads need to ground to the engine block so I think the problem is a grounding problem at the sender. I am going to a higher rated relay and will clean up the grounding issue as well. Due to change the anti freeze/coolant anyway. Let you all now what I find.
FYI, Ron Francis early wiring kits came with 30 amp resettable c.b.'s that tripped and knocked out the fan just when you needed it the most.
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