1970 Firewall Fuse Troubleshooting

[Tony J. Hurtado]

I am experience a problem with my TCS system on my 1970 big block 4-spd coupe and I may have narrowed it down to the Littelfuse Inc component on the firewall. I removed the connections at this fuse (3961573) and put a ohm meter on the prongs. I found that the lower one has continuity with the upper prong located nearest to the firewall but the upper prong on the engine side is open with respect to the other two.

If this part were properly functioning, should there be a closed loop on all prongs? Has anyone had experience rebuilding (or trying to rebuild) this component? What other vehicles of the era carried the same part?

[Joe L.]

Re: 1970 Firewall Fuse Troubleshooting

Tony-----

The component of which you speak is the TCS relay which was manufactured by automotive electrical components manufacturer Littlefuse. I can't advise relative to troubleshooting. However, be advised that the GM #3961573 relay is still available from GM. It carries a current GM list price of $8.73. In the event that, externally, the part differs in any way from your original, you may be able to use just the "guts" of the new part with your old case. In any event, you could use the part to easily ascertain if your old one is functioning properly. And, then you'd also have a spare as a hedge against the day that you can't get this part any longer.

[Tony J. Hurtado]

Re: 1970 Firewall Fuse Troubleshooting

Apparently, GM#3961573, the TCS relay, was recently discontinued. I found out through my local Chevy parts department. With their help, I was able to locate the part at another dealer and I should have their only TCS relay by next week.

Does anyone know what other vehicles used this relay?

[Joe L.]

Re: 1970 Firewall Fuse Troubleshooting

Tony-----

As far as Chevrolets go, the GM #3961573 was used on ALL 1970 passenger cars and on 1971-1975 Chevelles and Vegas. The relay was also used on certain Oldsmobiles, Pontiacs, and Buicks during the 1970-75 time period.

[Thad L.]

Re: 1970 Firewall Fuse Troubleshooting

Tony, I seem to remember someone told me or I read that the cover of this relay has a tiny date stamped on the top. So you may want to put your origional cover on your new relay assy! Thad LeJeune